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authorphajdan.jr@chromium.org <phajdan.jr@chromium.org@0039d316-1c4b-4281-b951-d872f2087c98>2010-08-18 23:37:03 +0000
committerphajdan.jr@chromium.org <phajdan.jr@chromium.org@0039d316-1c4b-4281-b951-d872f2087c98>2010-08-18 23:37:03 +0000
commite33cba46498a40774bc6d33a9258afbd5fa059e6 (patch)
tree4ce6b22f4f7b2b245b2d89bb9209a53e3274b263 /third_party/sqlite/src/where.c
parentaaf6472fd01db928919d4dc13687bde2a4b5c7b9 (diff)
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Move bundled copy of sqlite one level deeper to better separate it
from our patches, READMEs, etc. Also, add a shim header so we can use it for building with system sqlite. TEST=compile BUG=22208 Review URL: http://codereview.chromium.org/3108030 git-svn-id: svn://svn.chromium.org/chrome/trunk/src@56619 0039d316-1c4b-4281-b951-d872f2087c98
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diff --git a/third_party/sqlite/src/where.c b/third_party/sqlite/src/where.c
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-/*
-** 2001 September 15
-**
-** The author disclaims copyright to this source code. In place of
-** a legal notice, here is a blessing:
-**
-** May you do good and not evil.
-** May you find forgiveness for yourself and forgive others.
-** May you share freely, never taking more than you give.
-**
-*************************************************************************
-** This module contains C code that generates VDBE code used to process
-** the WHERE clause of SQL statements. This module is responsible for
-** generating the code that loops through a table looking for applicable
-** rows. Indices are selected and used to speed the search when doing
-** so is applicable. Because this module is responsible for selecting
-** indices, you might also think of this module as the "query optimizer".
-**
-** $Id: where.c,v 1.411 2009/07/31 06:14:52 danielk1977 Exp $
-*/
-#include "sqliteInt.h"
-
-/*
-** Trace output macros
-*/
-#if defined(SQLITE_TEST) || defined(SQLITE_DEBUG)
-int sqlite3WhereTrace = 0;
-#endif
-#if defined(SQLITE_TEST) && defined(SQLITE_DEBUG)
-# define WHERETRACE(X) if(sqlite3WhereTrace) sqlite3DebugPrintf X
-#else
-# define WHERETRACE(X)
-#endif
-
-/* Forward reference
-*/
-typedef struct WhereClause WhereClause;
-typedef struct WhereMaskSet WhereMaskSet;
-typedef struct WhereOrInfo WhereOrInfo;
-typedef struct WhereAndInfo WhereAndInfo;
-typedef struct WhereCost WhereCost;
-
-/*
-** The query generator uses an array of instances of this structure to
-** help it analyze the subexpressions of the WHERE clause. Each WHERE
-** clause subexpression is separated from the others by AND operators,
-** usually, or sometimes subexpressions separated by OR.
-**
-** All WhereTerms are collected into a single WhereClause structure.
-** The following identity holds:
-**
-** WhereTerm.pWC->a[WhereTerm.idx] == WhereTerm
-**
-** When a term is of the form:
-**
-** X <op> <expr>
-**
-** where X is a column name and <op> is one of certain operators,
-** then WhereTerm.leftCursor and WhereTerm.u.leftColumn record the
-** cursor number and column number for X. WhereTerm.eOperator records
-** the <op> using a bitmask encoding defined by WO_xxx below. The
-** use of a bitmask encoding for the operator allows us to search
-** quickly for terms that match any of several different operators.
-**
-** A WhereTerm might also be two or more subterms connected by OR:
-**
-** (t1.X <op> <expr>) OR (t1.Y <op> <expr>) OR ....
-**
-** In this second case, wtFlag as the TERM_ORINFO set and eOperator==WO_OR
-** and the WhereTerm.u.pOrInfo field points to auxiliary information that
-** is collected about the
-**
-** If a term in the WHERE clause does not match either of the two previous
-** categories, then eOperator==0. The WhereTerm.pExpr field is still set
-** to the original subexpression content and wtFlags is set up appropriately
-** but no other fields in the WhereTerm object are meaningful.
-**
-** When eOperator!=0, prereqRight and prereqAll record sets of cursor numbers,
-** but they do so indirectly. A single WhereMaskSet structure translates
-** cursor number into bits and the translated bit is stored in the prereq
-** fields. The translation is used in order to maximize the number of
-** bits that will fit in a Bitmask. The VDBE cursor numbers might be
-** spread out over the non-negative integers. For example, the cursor
-** numbers might be 3, 8, 9, 10, 20, 23, 41, and 45. The WhereMaskSet
-** translates these sparse cursor numbers into consecutive integers
-** beginning with 0 in order to make the best possible use of the available
-** bits in the Bitmask. So, in the example above, the cursor numbers
-** would be mapped into integers 0 through 7.
-**
-** The number of terms in a join is limited by the number of bits
-** in prereqRight and prereqAll. The default is 64 bits, hence SQLite
-** is only able to process joins with 64 or fewer tables.
-*/
-typedef struct WhereTerm WhereTerm;
-struct WhereTerm {
- Expr *pExpr; /* Pointer to the subexpression that is this term */
- int iParent; /* Disable pWC->a[iParent] when this term disabled */
- int leftCursor; /* Cursor number of X in "X <op> <expr>" */
- union {
- int leftColumn; /* Column number of X in "X <op> <expr>" */
- WhereOrInfo *pOrInfo; /* Extra information if eOperator==WO_OR */
- WhereAndInfo *pAndInfo; /* Extra information if eOperator==WO_AND */
- } u;
- u16 eOperator; /* A WO_xx value describing <op> */
- u8 wtFlags; /* TERM_xxx bit flags. See below */
- u8 nChild; /* Number of children that must disable us */
- WhereClause *pWC; /* The clause this term is part of */
- Bitmask prereqRight; /* Bitmask of tables used by pExpr->pRight */
- Bitmask prereqAll; /* Bitmask of tables referenced by pExpr */
-};
-
-/*
-** Allowed values of WhereTerm.wtFlags
-*/
-#define TERM_DYNAMIC 0x01 /* Need to call sqlite3ExprDelete(db, pExpr) */
-#define TERM_VIRTUAL 0x02 /* Added by the optimizer. Do not code */
-#define TERM_CODED 0x04 /* This term is already coded */
-#define TERM_COPIED 0x08 /* Has a child */
-#define TERM_ORINFO 0x10 /* Need to free the WhereTerm.u.pOrInfo object */
-#define TERM_ANDINFO 0x20 /* Need to free the WhereTerm.u.pAndInfo obj */
-#define TERM_OR_OK 0x40 /* Used during OR-clause processing */
-
-/*
-** An instance of the following structure holds all information about a
-** WHERE clause. Mostly this is a container for one or more WhereTerms.
-*/
-struct WhereClause {
- Parse *pParse; /* The parser context */
- WhereMaskSet *pMaskSet; /* Mapping of table cursor numbers to bitmasks */
- Bitmask vmask; /* Bitmask identifying virtual table cursors */
- u8 op; /* Split operator. TK_AND or TK_OR */
- int nTerm; /* Number of terms */
- int nSlot; /* Number of entries in a[] */
- WhereTerm *a; /* Each a[] describes a term of the WHERE cluase */
-#if defined(SQLITE_SMALL_STACK)
- WhereTerm aStatic[1]; /* Initial static space for a[] */
-#else
- WhereTerm aStatic[8]; /* Initial static space for a[] */
-#endif
-};
-
-/*
-** A WhereTerm with eOperator==WO_OR has its u.pOrInfo pointer set to
-** a dynamically allocated instance of the following structure.
-*/
-struct WhereOrInfo {
- WhereClause wc; /* Decomposition into subterms */
- Bitmask indexable; /* Bitmask of all indexable tables in the clause */
-};
-
-/*
-** A WhereTerm with eOperator==WO_AND has its u.pAndInfo pointer set to
-** a dynamically allocated instance of the following structure.
-*/
-struct WhereAndInfo {
- WhereClause wc; /* The subexpression broken out */
-};
-
-/*
-** An instance of the following structure keeps track of a mapping
-** between VDBE cursor numbers and bits of the bitmasks in WhereTerm.
-**
-** The VDBE cursor numbers are small integers contained in
-** SrcList_item.iCursor and Expr.iTable fields. For any given WHERE
-** clause, the cursor numbers might not begin with 0 and they might
-** contain gaps in the numbering sequence. But we want to make maximum
-** use of the bits in our bitmasks. This structure provides a mapping
-** from the sparse cursor numbers into consecutive integers beginning
-** with 0.
-**
-** If WhereMaskSet.ix[A]==B it means that The A-th bit of a Bitmask
-** corresponds VDBE cursor number B. The A-th bit of a bitmask is 1<<A.
-**
-** For example, if the WHERE clause expression used these VDBE
-** cursors: 4, 5, 8, 29, 57, 73. Then the WhereMaskSet structure
-** would map those cursor numbers into bits 0 through 5.
-**
-** Note that the mapping is not necessarily ordered. In the example
-** above, the mapping might go like this: 4->3, 5->1, 8->2, 29->0,
-** 57->5, 73->4. Or one of 719 other combinations might be used. It
-** does not really matter. What is important is that sparse cursor
-** numbers all get mapped into bit numbers that begin with 0 and contain
-** no gaps.
-*/
-struct WhereMaskSet {
- int n; /* Number of assigned cursor values */
- int ix[BMS]; /* Cursor assigned to each bit */
-};
-
-/*
-** A WhereCost object records a lookup strategy and the estimated
-** cost of pursuing that strategy.
-*/
-struct WhereCost {
- WherePlan plan; /* The lookup strategy */
- double rCost; /* Overall cost of pursuing this search strategy */
- double nRow; /* Estimated number of output rows */
- Bitmask used; /* Bitmask of cursors used by this plan */
-};
-
-/*
-** Bitmasks for the operators that indices are able to exploit. An
-** OR-ed combination of these values can be used when searching for
-** terms in the where clause.
-*/
-#define WO_IN 0x001
-#define WO_EQ 0x002
-#define WO_LT (WO_EQ<<(TK_LT-TK_EQ))
-#define WO_LE (WO_EQ<<(TK_LE-TK_EQ))
-#define WO_GT (WO_EQ<<(TK_GT-TK_EQ))
-#define WO_GE (WO_EQ<<(TK_GE-TK_EQ))
-#define WO_MATCH 0x040
-#define WO_ISNULL 0x080
-#define WO_OR 0x100 /* Two or more OR-connected terms */
-#define WO_AND 0x200 /* Two or more AND-connected terms */
-
-#define WO_ALL 0xfff /* Mask of all possible WO_* values */
-#define WO_SINGLE 0x0ff /* Mask of all non-compound WO_* values */
-
-/*
-** Value for wsFlags returned by bestIndex() and stored in
-** WhereLevel.wsFlags. These flags determine which search
-** strategies are appropriate.
-**
-** The least significant 12 bits is reserved as a mask for WO_ values above.
-** The WhereLevel.wsFlags field is usually set to WO_IN|WO_EQ|WO_ISNULL.
-** But if the table is the right table of a left join, WhereLevel.wsFlags
-** is set to WO_IN|WO_EQ. The WhereLevel.wsFlags field can then be used as
-** the "op" parameter to findTerm when we are resolving equality constraints.
-** ISNULL constraints will then not be used on the right table of a left
-** join. Tickets #2177 and #2189.
-*/
-#define WHERE_ROWID_EQ 0x00001000 /* rowid=EXPR or rowid IN (...) */
-#define WHERE_ROWID_RANGE 0x00002000 /* rowid<EXPR and/or rowid>EXPR */
-#define WHERE_COLUMN_EQ 0x00010000 /* x=EXPR or x IN (...) or x IS NULL */
-#define WHERE_COLUMN_RANGE 0x00020000 /* x<EXPR and/or x>EXPR */
-#define WHERE_COLUMN_IN 0x00040000 /* x IN (...) */
-#define WHERE_COLUMN_NULL 0x00080000 /* x IS NULL */
-#define WHERE_INDEXED 0x000f0000 /* Anything that uses an index */
-#define WHERE_IN_ABLE 0x000f1000 /* Able to support an IN operator */
-#define WHERE_TOP_LIMIT 0x00100000 /* x<EXPR or x<=EXPR constraint */
-#define WHERE_BTM_LIMIT 0x00200000 /* x>EXPR or x>=EXPR constraint */
-#define WHERE_IDX_ONLY 0x00800000 /* Use index only - omit table */
-#define WHERE_ORDERBY 0x01000000 /* Output will appear in correct order */
-#define WHERE_REVERSE 0x02000000 /* Scan in reverse order */
-#define WHERE_UNIQUE 0x04000000 /* Selects no more than one row */
-#define WHERE_VIRTUALTABLE 0x08000000 /* Use virtual-table processing */
-#define WHERE_MULTI_OR 0x10000000 /* OR using multiple indices */
-
-/*
-** Initialize a preallocated WhereClause structure.
-*/
-static void whereClauseInit(
- WhereClause *pWC, /* The WhereClause to be initialized */
- Parse *pParse, /* The parsing context */
- WhereMaskSet *pMaskSet /* Mapping from table cursor numbers to bitmasks */
-){
- pWC->pParse = pParse;
- pWC->pMaskSet = pMaskSet;
- pWC->nTerm = 0;
- pWC->nSlot = ArraySize(pWC->aStatic);
- pWC->a = pWC->aStatic;
- pWC->vmask = 0;
-}
-
-/* Forward reference */
-static void whereClauseClear(WhereClause*);
-
-/*
-** Deallocate all memory associated with a WhereOrInfo object.
-*/
-static void whereOrInfoDelete(sqlite3 *db, WhereOrInfo *p){
- whereClauseClear(&p->wc);
- sqlite3DbFree(db, p);
-}
-
-/*
-** Deallocate all memory associated with a WhereAndInfo object.
-*/
-static void whereAndInfoDelete(sqlite3 *db, WhereAndInfo *p){
- whereClauseClear(&p->wc);
- sqlite3DbFree(db, p);
-}
-
-/*
-** Deallocate a WhereClause structure. The WhereClause structure
-** itself is not freed. This routine is the inverse of whereClauseInit().
-*/
-static void whereClauseClear(WhereClause *pWC){
- int i;
- WhereTerm *a;
- sqlite3 *db = pWC->pParse->db;
- for(i=pWC->nTerm-1, a=pWC->a; i>=0; i--, a++){
- if( a->wtFlags & TERM_DYNAMIC ){
- sqlite3ExprDelete(db, a->pExpr);
- }
- if( a->wtFlags & TERM_ORINFO ){
- whereOrInfoDelete(db, a->u.pOrInfo);
- }else if( a->wtFlags & TERM_ANDINFO ){
- whereAndInfoDelete(db, a->u.pAndInfo);
- }
- }
- if( pWC->a!=pWC->aStatic ){
- sqlite3DbFree(db, pWC->a);
- }
-}
-
-/*
-** Add a single new WhereTerm entry to the WhereClause object pWC.
-** The new WhereTerm object is constructed from Expr p and with wtFlags.
-** The index in pWC->a[] of the new WhereTerm is returned on success.
-** 0 is returned if the new WhereTerm could not be added due to a memory
-** allocation error. The memory allocation failure will be recorded in
-** the db->mallocFailed flag so that higher-level functions can detect it.
-**
-** This routine will increase the size of the pWC->a[] array as necessary.
-**
-** If the wtFlags argument includes TERM_DYNAMIC, then responsibility
-** for freeing the expression p is assumed by the WhereClause object pWC.
-** This is true even if this routine fails to allocate a new WhereTerm.
-**
-** WARNING: This routine might reallocate the space used to store
-** WhereTerms. All pointers to WhereTerms should be invalidated after
-** calling this routine. Such pointers may be reinitialized by referencing
-** the pWC->a[] array.
-*/
-static int whereClauseInsert(WhereClause *pWC, Expr *p, u8 wtFlags){
- WhereTerm *pTerm;
- int idx;
- if( pWC->nTerm>=pWC->nSlot ){
- WhereTerm *pOld = pWC->a;
- sqlite3 *db = pWC->pParse->db;
- pWC->a = sqlite3DbMallocRaw(db, sizeof(pWC->a[0])*pWC->nSlot*2 );
- if( pWC->a==0 ){
- if( wtFlags & TERM_DYNAMIC ){
- sqlite3ExprDelete(db, p);
- }
- pWC->a = pOld;
- return 0;
- }
- memcpy(pWC->a, pOld, sizeof(pWC->a[0])*pWC->nTerm);
- if( pOld!=pWC->aStatic ){
- sqlite3DbFree(db, pOld);
- }
- pWC->nSlot = sqlite3DbMallocSize(db, pWC->a)/sizeof(pWC->a[0]);
- }
- pTerm = &pWC->a[idx = pWC->nTerm++];
- pTerm->pExpr = p;
- pTerm->wtFlags = wtFlags;
- pTerm->pWC = pWC;
- pTerm->iParent = -1;
- return idx;
-}
-
-/*
-** This routine identifies subexpressions in the WHERE clause where
-** each subexpression is separated by the AND operator or some other
-** operator specified in the op parameter. The WhereClause structure
-** is filled with pointers to subexpressions. For example:
-**
-** WHERE a=='hello' AND coalesce(b,11)<10 AND (c+12!=d OR c==22)
-** \________/ \_______________/ \________________/
-** slot[0] slot[1] slot[2]
-**
-** The original WHERE clause in pExpr is unaltered. All this routine
-** does is make slot[] entries point to substructure within pExpr.
-**
-** In the previous sentence and in the diagram, "slot[]" refers to
-** the WhereClause.a[] array. The slot[] array grows as needed to contain
-** all terms of the WHERE clause.
-*/
-static void whereSplit(WhereClause *pWC, Expr *pExpr, int op){
- pWC->op = (u8)op;
- if( pExpr==0 ) return;
- if( pExpr->op!=op ){
- whereClauseInsert(pWC, pExpr, 0);
- }else{
- whereSplit(pWC, pExpr->pLeft, op);
- whereSplit(pWC, pExpr->pRight, op);
- }
-}
-
-/*
-** Initialize an expression mask set (a WhereMaskSet object)
-*/
-#define initMaskSet(P) memset(P, 0, sizeof(*P))
-
-/*
-** Return the bitmask for the given cursor number. Return 0 if
-** iCursor is not in the set.
-*/
-static Bitmask getMask(WhereMaskSet *pMaskSet, int iCursor){
- int i;
- assert( pMaskSet->n<=sizeof(Bitmask)*8 );
- for(i=0; i<pMaskSet->n; i++){
- if( pMaskSet->ix[i]==iCursor ){
- return ((Bitmask)1)<<i;
- }
- }
- return 0;
-}
-
-/*
-** Create a new mask for cursor iCursor.
-**
-** There is one cursor per table in the FROM clause. The number of
-** tables in the FROM clause is limited by a test early in the
-** sqlite3WhereBegin() routine. So we know that the pMaskSet->ix[]
-** array will never overflow.
-*/
-static void createMask(WhereMaskSet *pMaskSet, int iCursor){
- assert( pMaskSet->n < ArraySize(pMaskSet->ix) );
- pMaskSet->ix[pMaskSet->n++] = iCursor;
-}
-
-/*
-** This routine walks (recursively) an expression tree and generates
-** a bitmask indicating which tables are used in that expression
-** tree.
-**
-** In order for this routine to work, the calling function must have
-** previously invoked sqlite3ResolveExprNames() on the expression. See
-** the header comment on that routine for additional information.
-** The sqlite3ResolveExprNames() routines looks for column names and
-** sets their opcodes to TK_COLUMN and their Expr.iTable fields to
-** the VDBE cursor number of the table. This routine just has to
-** translate the cursor numbers into bitmask values and OR all
-** the bitmasks together.
-*/
-static Bitmask exprListTableUsage(WhereMaskSet*, ExprList*);
-static Bitmask exprSelectTableUsage(WhereMaskSet*, Select*);
-static Bitmask exprTableUsage(WhereMaskSet *pMaskSet, Expr *p){
- Bitmask mask = 0;
- if( p==0 ) return 0;
- if( p->op==TK_COLUMN ){
- mask = getMask(pMaskSet, p->iTable);
- return mask;
- }
- mask = exprTableUsage(pMaskSet, p->pRight);
- mask |= exprTableUsage(pMaskSet, p->pLeft);
- if( ExprHasProperty(p, EP_xIsSelect) ){
- mask |= exprSelectTableUsage(pMaskSet, p->x.pSelect);
- }else{
- mask |= exprListTableUsage(pMaskSet, p->x.pList);
- }
- return mask;
-}
-static Bitmask exprListTableUsage(WhereMaskSet *pMaskSet, ExprList *pList){
- int i;
- Bitmask mask = 0;
- if( pList ){
- for(i=0; i<pList->nExpr; i++){
- mask |= exprTableUsage(pMaskSet, pList->a[i].pExpr);
- }
- }
- return mask;
-}
-static Bitmask exprSelectTableUsage(WhereMaskSet *pMaskSet, Select *pS){
- Bitmask mask = 0;
- while( pS ){
- mask |= exprListTableUsage(pMaskSet, pS->pEList);
- mask |= exprListTableUsage(pMaskSet, pS->pGroupBy);
- mask |= exprListTableUsage(pMaskSet, pS->pOrderBy);
- mask |= exprTableUsage(pMaskSet, pS->pWhere);
- mask |= exprTableUsage(pMaskSet, pS->pHaving);
- pS = pS->pPrior;
- }
- return mask;
-}
-
-/*
-** Return TRUE if the given operator is one of the operators that is
-** allowed for an indexable WHERE clause term. The allowed operators are
-** "=", "<", ">", "<=", ">=", and "IN".
-*/
-static int allowedOp(int op){
- assert( TK_GT>TK_EQ && TK_GT<TK_GE );
- assert( TK_LT>TK_EQ && TK_LT<TK_GE );
- assert( TK_LE>TK_EQ && TK_LE<TK_GE );
- assert( TK_GE==TK_EQ+4 );
- return op==TK_IN || (op>=TK_EQ && op<=TK_GE) || op==TK_ISNULL;
-}
-
-/*
-** Swap two objects of type TYPE.
-*/
-#define SWAP(TYPE,A,B) {TYPE t=A; A=B; B=t;}
-
-/*
-** Commute a comparison operator. Expressions of the form "X op Y"
-** are converted into "Y op X".
-**
-** If a collation sequence is associated with either the left or right
-** side of the comparison, it remains associated with the same side after
-** the commutation. So "Y collate NOCASE op X" becomes
-** "X collate NOCASE op Y". This is because any collation sequence on
-** the left hand side of a comparison overrides any collation sequence
-** attached to the right. For the same reason the EP_ExpCollate flag
-** is not commuted.
-*/
-static void exprCommute(Parse *pParse, Expr *pExpr){
- u16 expRight = (pExpr->pRight->flags & EP_ExpCollate);
- u16 expLeft = (pExpr->pLeft->flags & EP_ExpCollate);
- assert( allowedOp(pExpr->op) && pExpr->op!=TK_IN );
- pExpr->pRight->pColl = sqlite3ExprCollSeq(pParse, pExpr->pRight);
- pExpr->pLeft->pColl = sqlite3ExprCollSeq(pParse, pExpr->pLeft);
- SWAP(CollSeq*,pExpr->pRight->pColl,pExpr->pLeft->pColl);
- pExpr->pRight->flags = (pExpr->pRight->flags & ~EP_ExpCollate) | expLeft;
- pExpr->pLeft->flags = (pExpr->pLeft->flags & ~EP_ExpCollate) | expRight;
- SWAP(Expr*,pExpr->pRight,pExpr->pLeft);
- if( pExpr->op>=TK_GT ){
- assert( TK_LT==TK_GT+2 );
- assert( TK_GE==TK_LE+2 );
- assert( TK_GT>TK_EQ );
- assert( TK_GT<TK_LE );
- assert( pExpr->op>=TK_GT && pExpr->op<=TK_GE );
- pExpr->op = ((pExpr->op-TK_GT)^2)+TK_GT;
- }
-}
-
-/*
-** Translate from TK_xx operator to WO_xx bitmask.
-*/
-static u16 operatorMask(int op){
- u16 c;
- assert( allowedOp(op) );
- if( op==TK_IN ){
- c = WO_IN;
- }else if( op==TK_ISNULL ){
- c = WO_ISNULL;
- }else{
- assert( (WO_EQ<<(op-TK_EQ)) < 0x7fff );
- c = (u16)(WO_EQ<<(op-TK_EQ));
- }
- assert( op!=TK_ISNULL || c==WO_ISNULL );
- assert( op!=TK_IN || c==WO_IN );
- assert( op!=TK_EQ || c==WO_EQ );
- assert( op!=TK_LT || c==WO_LT );
- assert( op!=TK_LE || c==WO_LE );
- assert( op!=TK_GT || c==WO_GT );
- assert( op!=TK_GE || c==WO_GE );
- return c;
-}
-
-/*
-** Search for a term in the WHERE clause that is of the form "X <op> <expr>"
-** where X is a reference to the iColumn of table iCur and <op> is one of
-** the WO_xx operator codes specified by the op parameter.
-** Return a pointer to the term. Return 0 if not found.
-*/
-static WhereTerm *findTerm(
- WhereClause *pWC, /* The WHERE clause to be searched */
- int iCur, /* Cursor number of LHS */
- int iColumn, /* Column number of LHS */
- Bitmask notReady, /* RHS must not overlap with this mask */
- u32 op, /* Mask of WO_xx values describing operator */
- Index *pIdx /* Must be compatible with this index, if not NULL */
-){
- WhereTerm *pTerm;
- int k;
- assert( iCur>=0 );
- op &= WO_ALL;
- for(pTerm=pWC->a, k=pWC->nTerm; k; k--, pTerm++){
- if( pTerm->leftCursor==iCur
- && (pTerm->prereqRight & notReady)==0
- && pTerm->u.leftColumn==iColumn
- && (pTerm->eOperator & op)!=0
- ){
- if( pIdx && pTerm->eOperator!=WO_ISNULL ){
- Expr *pX = pTerm->pExpr;
- CollSeq *pColl;
- char idxaff;
- int j;
- Parse *pParse = pWC->pParse;
-
- idxaff = pIdx->pTable->aCol[iColumn].affinity;
- if( !sqlite3IndexAffinityOk(pX, idxaff) ) continue;
-
- /* Figure out the collation sequence required from an index for
- ** it to be useful for optimising expression pX. Store this
- ** value in variable pColl.
- */
- assert(pX->pLeft);
- pColl = sqlite3BinaryCompareCollSeq(pParse, pX->pLeft, pX->pRight);
- assert(pColl || pParse->nErr);
-
- for(j=0; pIdx->aiColumn[j]!=iColumn; j++){
- if( NEVER(j>=pIdx->nColumn) ) return 0;
- }
- if( pColl && sqlite3StrICmp(pColl->zName, pIdx->azColl[j]) ) continue;
- }
- return pTerm;
- }
- }
- return 0;
-}
-
-/* Forward reference */
-static void exprAnalyze(SrcList*, WhereClause*, int);
-
-/*
-** Call exprAnalyze on all terms in a WHERE clause.
-**
-**
-*/
-static void exprAnalyzeAll(
- SrcList *pTabList, /* the FROM clause */
- WhereClause *pWC /* the WHERE clause to be analyzed */
-){
- int i;
- for(i=pWC->nTerm-1; i>=0; i--){
- exprAnalyze(pTabList, pWC, i);
- }
-}
-
-#ifndef SQLITE_OMIT_LIKE_OPTIMIZATION
-/*
-** Check to see if the given expression is a LIKE or GLOB operator that
-** can be optimized using inequality constraints. Return TRUE if it is
-** so and false if not.
-**
-** In order for the operator to be optimizible, the RHS must be a string
-** literal that does not begin with a wildcard.
-*/
-static int isLikeOrGlob(
- Parse *pParse, /* Parsing and code generating context */
- Expr *pExpr, /* Test this expression */
- int *pnPattern, /* Number of non-wildcard prefix characters */
- int *pisComplete, /* True if the only wildcard is % in the last character */
- int *pnoCase /* True if uppercase is equivalent to lowercase */
-){
- const char *z; /* String on RHS of LIKE operator */
- Expr *pRight, *pLeft; /* Right and left size of LIKE operator */
- ExprList *pList; /* List of operands to the LIKE operator */
- int c; /* One character in z[] */
- int cnt; /* Number of non-wildcard prefix characters */
- char wc[3]; /* Wildcard characters */
- CollSeq *pColl; /* Collating sequence for LHS */
- sqlite3 *db = pParse->db; /* Database connection */
-
- if( !sqlite3IsLikeFunction(db, pExpr, pnoCase, wc) ){
- return 0;
- }
-#ifdef SQLITE_EBCDIC
- if( *pnoCase ) return 0;
-#endif
- pList = pExpr->x.pList;
- pRight = pList->a[0].pExpr;
- if( pRight->op!=TK_STRING ){
- return 0;
- }
- pLeft = pList->a[1].pExpr;
- if( pLeft->op!=TK_COLUMN ){
- return 0;
- }
- pColl = sqlite3ExprCollSeq(pParse, pLeft);
- assert( pColl!=0 || pLeft->iColumn==-1 );
- if( pColl==0 ) return 0;
- if( (pColl->type!=SQLITE_COLL_BINARY || *pnoCase) &&
- (pColl->type!=SQLITE_COLL_NOCASE || !*pnoCase) ){
- return 0;
- }
- if( sqlite3ExprAffinity(pLeft)!=SQLITE_AFF_TEXT ) return 0;
- z = pRight->u.zToken;
- if( ALWAYS(z) ){
- cnt = 0;
- while( (c=z[cnt])!=0 && c!=wc[0] && c!=wc[1] && c!=wc[2] ){
- cnt++;
- }
- if( cnt!=0 && c!=0 && 255!=(u8)z[cnt-1] ){
- *pisComplete = z[cnt]==wc[0] && z[cnt+1]==0;
- *pnPattern = cnt;
- return 1;
- }
- }
- return 0;
-}
-#endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */
-
-
-#ifndef SQLITE_OMIT_VIRTUALTABLE
-/*
-** Check to see if the given expression is of the form
-**
-** column MATCH expr
-**
-** If it is then return TRUE. If not, return FALSE.
-*/
-static int isMatchOfColumn(
- Expr *pExpr /* Test this expression */
-){
- ExprList *pList;
-
- if( pExpr->op!=TK_FUNCTION ){
- return 0;
- }
- if( sqlite3StrICmp(pExpr->u.zToken,"match")!=0 ){
- return 0;
- }
- pList = pExpr->x.pList;
- if( pList->nExpr!=2 ){
- return 0;
- }
- if( pList->a[1].pExpr->op != TK_COLUMN ){
- return 0;
- }
- return 1;
-}
-#endif /* SQLITE_OMIT_VIRTUALTABLE */
-
-/*
-** If the pBase expression originated in the ON or USING clause of
-** a join, then transfer the appropriate markings over to derived.
-*/
-static void transferJoinMarkings(Expr *pDerived, Expr *pBase){
- pDerived->flags |= pBase->flags & EP_FromJoin;
- pDerived->iRightJoinTable = pBase->iRightJoinTable;
-}
-
-#if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY)
-/*
-** Analyze a term that consists of two or more OR-connected
-** subterms. So in:
-**
-** ... WHERE (a=5) AND (b=7 OR c=9 OR d=13) AND (d=13)
-** ^^^^^^^^^^^^^^^^^^^^
-**
-** This routine analyzes terms such as the middle term in the above example.
-** A WhereOrTerm object is computed and attached to the term under
-** analysis, regardless of the outcome of the analysis. Hence:
-**
-** WhereTerm.wtFlags |= TERM_ORINFO
-** WhereTerm.u.pOrInfo = a dynamically allocated WhereOrTerm object
-**
-** The term being analyzed must have two or more of OR-connected subterms.
-** A single subterm might be a set of AND-connected sub-subterms.
-** Examples of terms under analysis:
-**
-** (A) t1.x=t2.y OR t1.x=t2.z OR t1.y=15 OR t1.z=t3.a+5
-** (B) x=expr1 OR expr2=x OR x=expr3
-** (C) t1.x=t2.y OR (t1.x=t2.z AND t1.y=15)
-** (D) x=expr1 OR (y>11 AND y<22 AND z LIKE '*hello*')
-** (E) (p.a=1 AND q.b=2 AND r.c=3) OR (p.x=4 AND q.y=5 AND r.z=6)
-**
-** CASE 1:
-**
-** If all subterms are of the form T.C=expr for some single column of C
-** a single table T (as shown in example B above) then create a new virtual
-** term that is an equivalent IN expression. In other words, if the term
-** being analyzed is:
-**
-** x = expr1 OR expr2 = x OR x = expr3
-**
-** then create a new virtual term like this:
-**
-** x IN (expr1,expr2,expr3)
-**
-** CASE 2:
-**
-** If all subterms are indexable by a single table T, then set
-**
-** WhereTerm.eOperator = WO_OR
-** WhereTerm.u.pOrInfo->indexable |= the cursor number for table T
-**
-** A subterm is "indexable" if it is of the form
-** "T.C <op> <expr>" where C is any column of table T and
-** <op> is one of "=", "<", "<=", ">", ">=", "IS NULL", or "IN".
-** A subterm is also indexable if it is an AND of two or more
-** subsubterms at least one of which is indexable. Indexable AND
-** subterms have their eOperator set to WO_AND and they have
-** u.pAndInfo set to a dynamically allocated WhereAndTerm object.
-**
-** From another point of view, "indexable" means that the subterm could
-** potentially be used with an index if an appropriate index exists.
-** This analysis does not consider whether or not the index exists; that
-** is something the bestIndex() routine will determine. This analysis
-** only looks at whether subterms appropriate for indexing exist.
-**
-** All examples A through E above all satisfy case 2. But if a term
-** also statisfies case 1 (such as B) we know that the optimizer will
-** always prefer case 1, so in that case we pretend that case 2 is not
-** satisfied.
-**
-** It might be the case that multiple tables are indexable. For example,
-** (E) above is indexable on tables P, Q, and R.
-**
-** Terms that satisfy case 2 are candidates for lookup by using
-** separate indices to find rowids for each subterm and composing
-** the union of all rowids using a RowSet object. This is similar
-** to "bitmap indices" in other database engines.
-**
-** OTHERWISE:
-**
-** If neither case 1 nor case 2 apply, then leave the eOperator set to
-** zero. This term is not useful for search.
-*/
-static void exprAnalyzeOrTerm(
- SrcList *pSrc, /* the FROM clause */
- WhereClause *pWC, /* the complete WHERE clause */
- int idxTerm /* Index of the OR-term to be analyzed */
-){
- Parse *pParse = pWC->pParse; /* Parser context */
- sqlite3 *db = pParse->db; /* Database connection */
- WhereTerm *pTerm = &pWC->a[idxTerm]; /* The term to be analyzed */
- Expr *pExpr = pTerm->pExpr; /* The expression of the term */
- WhereMaskSet *pMaskSet = pWC->pMaskSet; /* Table use masks */
- int i; /* Loop counters */
- WhereClause *pOrWc; /* Breakup of pTerm into subterms */
- WhereTerm *pOrTerm; /* A Sub-term within the pOrWc */
- WhereOrInfo *pOrInfo; /* Additional information associated with pTerm */
- Bitmask chngToIN; /* Tables that might satisfy case 1 */
- Bitmask indexable; /* Tables that are indexable, satisfying case 2 */
-
- /*
- ** Break the OR clause into its separate subterms. The subterms are
- ** stored in a WhereClause structure containing within the WhereOrInfo
- ** object that is attached to the original OR clause term.
- */
- assert( (pTerm->wtFlags & (TERM_DYNAMIC|TERM_ORINFO|TERM_ANDINFO))==0 );
- assert( pExpr->op==TK_OR );
- pTerm->u.pOrInfo = pOrInfo = sqlite3DbMallocZero(db, sizeof(*pOrInfo));
- if( pOrInfo==0 ) return;
- pTerm->wtFlags |= TERM_ORINFO;
- pOrWc = &pOrInfo->wc;
- whereClauseInit(pOrWc, pWC->pParse, pMaskSet);
- whereSplit(pOrWc, pExpr, TK_OR);
- exprAnalyzeAll(pSrc, pOrWc);
- if( db->mallocFailed ) return;
- assert( pOrWc->nTerm>=2 );
-
- /*
- ** Compute the set of tables that might satisfy cases 1 or 2.
- */
- indexable = ~(Bitmask)0;
- chngToIN = ~(pWC->vmask);
- for(i=pOrWc->nTerm-1, pOrTerm=pOrWc->a; i>=0 && indexable; i--, pOrTerm++){
- if( (pOrTerm->eOperator & WO_SINGLE)==0 ){
- WhereAndInfo *pAndInfo;
- assert( pOrTerm->eOperator==0 );
- assert( (pOrTerm->wtFlags & (TERM_ANDINFO|TERM_ORINFO))==0 );
- chngToIN = 0;
- pAndInfo = sqlite3DbMallocRaw(db, sizeof(*pAndInfo));
- if( pAndInfo ){
- WhereClause *pAndWC;
- WhereTerm *pAndTerm;
- int j;
- Bitmask b = 0;
- pOrTerm->u.pAndInfo = pAndInfo;
- pOrTerm->wtFlags |= TERM_ANDINFO;
- pOrTerm->eOperator = WO_AND;
- pAndWC = &pAndInfo->wc;
- whereClauseInit(pAndWC, pWC->pParse, pMaskSet);
- whereSplit(pAndWC, pOrTerm->pExpr, TK_AND);
- exprAnalyzeAll(pSrc, pAndWC);
- testcase( db->mallocFailed );
- if( !db->mallocFailed ){
- for(j=0, pAndTerm=pAndWC->a; j<pAndWC->nTerm; j++, pAndTerm++){
- assert( pAndTerm->pExpr );
- if( allowedOp(pAndTerm->pExpr->op) ){
- b |= getMask(pMaskSet, pAndTerm->leftCursor);
- }
- }
- }
- indexable &= b;
- }
- }else if( pOrTerm->wtFlags & TERM_COPIED ){
- /* Skip this term for now. We revisit it when we process the
- ** corresponding TERM_VIRTUAL term */
- }else{
- Bitmask b;
- b = getMask(pMaskSet, pOrTerm->leftCursor);
- if( pOrTerm->wtFlags & TERM_VIRTUAL ){
- WhereTerm *pOther = &pOrWc->a[pOrTerm->iParent];
- b |= getMask(pMaskSet, pOther->leftCursor);
- }
- indexable &= b;
- if( pOrTerm->eOperator!=WO_EQ ){
- chngToIN = 0;
- }else{
- chngToIN &= b;
- }
- }
- }
-
- /*
- ** Record the set of tables that satisfy case 2. The set might be
- ** empty.
- */
- pOrInfo->indexable = indexable;
- pTerm->eOperator = indexable==0 ? 0 : WO_OR;
-
- /*
- ** chngToIN holds a set of tables that *might* satisfy case 1. But
- ** we have to do some additional checking to see if case 1 really
- ** is satisfied.
- **
- ** chngToIN will hold either 0, 1, or 2 bits. The 0-bit case means
- ** that there is no possibility of transforming the OR clause into an
- ** IN operator because one or more terms in the OR clause contain
- ** something other than == on a column in the single table. The 1-bit
- ** case means that every term of the OR clause is of the form
- ** "table.column=expr" for some single table. The one bit that is set
- ** will correspond to the common table. We still need to check to make
- ** sure the same column is used on all terms. The 2-bit case is when
- ** the all terms are of the form "table1.column=table2.column". It
- ** might be possible to form an IN operator with either table1.column
- ** or table2.column as the LHS if either is common to every term of
- ** the OR clause.
- **
- ** Note that terms of the form "table.column1=table.column2" (the
- ** same table on both sizes of the ==) cannot be optimized.
- */
- if( chngToIN ){
- int okToChngToIN = 0; /* True if the conversion to IN is valid */
- int iColumn = -1; /* Column index on lhs of IN operator */
- int iCursor = -1; /* Table cursor common to all terms */
- int j = 0; /* Loop counter */
-
- /* Search for a table and column that appears on one side or the
- ** other of the == operator in every subterm. That table and column
- ** will be recorded in iCursor and iColumn. There might not be any
- ** such table and column. Set okToChngToIN if an appropriate table
- ** and column is found but leave okToChngToIN false if not found.
- */
- for(j=0; j<2 && !okToChngToIN; j++){
- pOrTerm = pOrWc->a;
- for(i=pOrWc->nTerm-1; i>=0; i--, pOrTerm++){
- assert( pOrTerm->eOperator==WO_EQ );
- pOrTerm->wtFlags &= ~TERM_OR_OK;
- if( pOrTerm->leftCursor==iCursor ){
- /* This is the 2-bit case and we are on the second iteration and
- ** current term is from the first iteration. So skip this term. */
- assert( j==1 );
- continue;
- }
- if( (chngToIN & getMask(pMaskSet, pOrTerm->leftCursor))==0 ){
- /* This term must be of the form t1.a==t2.b where t2 is in the
- ** chngToIN set but t1 is not. This term will be either preceeded
- ** or follwed by an inverted copy (t2.b==t1.a). Skip this term
- ** and use its inversion. */
- testcase( pOrTerm->wtFlags & TERM_COPIED );
- testcase( pOrTerm->wtFlags & TERM_VIRTUAL );
- assert( pOrTerm->wtFlags & (TERM_COPIED|TERM_VIRTUAL) );
- continue;
- }
- iColumn = pOrTerm->u.leftColumn;
- iCursor = pOrTerm->leftCursor;
- break;
- }
- if( i<0 ){
- /* No candidate table+column was found. This can only occur
- ** on the second iteration */
- assert( j==1 );
- assert( (chngToIN&(chngToIN-1))==0 );
- assert( chngToIN==getMask(pMaskSet, iCursor) );
- break;
- }
- testcase( j==1 );
-
- /* We have found a candidate table and column. Check to see if that
- ** table and column is common to every term in the OR clause */
- okToChngToIN = 1;
- for(; i>=0 && okToChngToIN; i--, pOrTerm++){
- assert( pOrTerm->eOperator==WO_EQ );
- if( pOrTerm->leftCursor!=iCursor ){
- pOrTerm->wtFlags &= ~TERM_OR_OK;
- }else if( pOrTerm->u.leftColumn!=iColumn ){
- okToChngToIN = 0;
- }else{
- int affLeft, affRight;
- /* If the right-hand side is also a column, then the affinities
- ** of both right and left sides must be such that no type
- ** conversions are required on the right. (Ticket #2249)
- */
- affRight = sqlite3ExprAffinity(pOrTerm->pExpr->pRight);
- affLeft = sqlite3ExprAffinity(pOrTerm->pExpr->pLeft);
- if( affRight!=0 && affRight!=affLeft ){
- okToChngToIN = 0;
- }else{
- pOrTerm->wtFlags |= TERM_OR_OK;
- }
- }
- }
- }
-
- /* At this point, okToChngToIN is true if original pTerm satisfies
- ** case 1. In that case, construct a new virtual term that is
- ** pTerm converted into an IN operator.
- */
- if( okToChngToIN ){
- Expr *pDup; /* A transient duplicate expression */
- ExprList *pList = 0; /* The RHS of the IN operator */
- Expr *pLeft = 0; /* The LHS of the IN operator */
- Expr *pNew; /* The complete IN operator */
-
- for(i=pOrWc->nTerm-1, pOrTerm=pOrWc->a; i>=0; i--, pOrTerm++){
- if( (pOrTerm->wtFlags & TERM_OR_OK)==0 ) continue;
- assert( pOrTerm->eOperator==WO_EQ );
- assert( pOrTerm->leftCursor==iCursor );
- assert( pOrTerm->u.leftColumn==iColumn );
- pDup = sqlite3ExprDup(db, pOrTerm->pExpr->pRight, 0);
- pList = sqlite3ExprListAppend(pWC->pParse, pList, pDup);
- pLeft = pOrTerm->pExpr->pLeft;
- }
- assert( pLeft!=0 );
- pDup = sqlite3ExprDup(db, pLeft, 0);
- pNew = sqlite3PExpr(pParse, TK_IN, pDup, 0, 0);
- if( pNew ){
- int idxNew;
- transferJoinMarkings(pNew, pExpr);
- assert( !ExprHasProperty(pNew, EP_xIsSelect) );
- pNew->x.pList = pList;
- idxNew = whereClauseInsert(pWC, pNew, TERM_VIRTUAL|TERM_DYNAMIC);
- testcase( idxNew==0 );
- exprAnalyze(pSrc, pWC, idxNew);
- pTerm = &pWC->a[idxTerm];
- pWC->a[idxNew].iParent = idxTerm;
- pTerm->nChild = 1;
- }else{
- sqlite3ExprListDelete(db, pList);
- }
- pTerm->eOperator = 0; /* case 1 trumps case 2 */
- }
- }
-}
-#endif /* !SQLITE_OMIT_OR_OPTIMIZATION && !SQLITE_OMIT_SUBQUERY */
-
-
-/*
-** The input to this routine is an WhereTerm structure with only the
-** "pExpr" field filled in. The job of this routine is to analyze the
-** subexpression and populate all the other fields of the WhereTerm
-** structure.
-**
-** If the expression is of the form "<expr> <op> X" it gets commuted
-** to the standard form of "X <op> <expr>".
-**
-** If the expression is of the form "X <op> Y" where both X and Y are
-** columns, then the original expression is unchanged and a new virtual
-** term of the form "Y <op> X" is added to the WHERE clause and
-** analyzed separately. The original term is marked with TERM_COPIED
-** and the new term is marked with TERM_DYNAMIC (because it's pExpr
-** needs to be freed with the WhereClause) and TERM_VIRTUAL (because it
-** is a commuted copy of a prior term.) The original term has nChild=1
-** and the copy has idxParent set to the index of the original term.
-*/
-static void exprAnalyze(
- SrcList *pSrc, /* the FROM clause */
- WhereClause *pWC, /* the WHERE clause */
- int idxTerm /* Index of the term to be analyzed */
-){
- WhereTerm *pTerm; /* The term to be analyzed */
- WhereMaskSet *pMaskSet; /* Set of table index masks */
- Expr *pExpr; /* The expression to be analyzed */
- Bitmask prereqLeft; /* Prerequesites of the pExpr->pLeft */
- Bitmask prereqAll; /* Prerequesites of pExpr */
- Bitmask extraRight = 0;
- int nPattern;
- int isComplete;
- int noCase;
- int op; /* Top-level operator. pExpr->op */
- Parse *pParse = pWC->pParse; /* Parsing context */
- sqlite3 *db = pParse->db; /* Database connection */
-
- if( db->mallocFailed ){
- return;
- }
- pTerm = &pWC->a[idxTerm];
- pMaskSet = pWC->pMaskSet;
- pExpr = pTerm->pExpr;
- prereqLeft = exprTableUsage(pMaskSet, pExpr->pLeft);
- op = pExpr->op;
- if( op==TK_IN ){
- assert( pExpr->pRight==0 );
- if( ExprHasProperty(pExpr, EP_xIsSelect) ){
- pTerm->prereqRight = exprSelectTableUsage(pMaskSet, pExpr->x.pSelect);
- }else{
- pTerm->prereqRight = exprListTableUsage(pMaskSet, pExpr->x.pList);
- }
- }else if( op==TK_ISNULL ){
- pTerm->prereqRight = 0;
- }else{
- pTerm->prereqRight = exprTableUsage(pMaskSet, pExpr->pRight);
- }
- prereqAll = exprTableUsage(pMaskSet, pExpr);
- if( ExprHasProperty(pExpr, EP_FromJoin) ){
- Bitmask x = getMask(pMaskSet, pExpr->iRightJoinTable);
- prereqAll |= x;
- extraRight = x-1; /* ON clause terms may not be used with an index
- ** on left table of a LEFT JOIN. Ticket #3015 */
- }
- pTerm->prereqAll = prereqAll;
- pTerm->leftCursor = -1;
- pTerm->iParent = -1;
- pTerm->eOperator = 0;
- if( allowedOp(op) && (pTerm->prereqRight & prereqLeft)==0 ){
- Expr *pLeft = pExpr->pLeft;
- Expr *pRight = pExpr->pRight;
- if( pLeft->op==TK_COLUMN ){
- pTerm->leftCursor = pLeft->iTable;
- pTerm->u.leftColumn = pLeft->iColumn;
- pTerm->eOperator = operatorMask(op);
- }
- if( pRight && pRight->op==TK_COLUMN ){
- WhereTerm *pNew;
- Expr *pDup;
- if( pTerm->leftCursor>=0 ){
- int idxNew;
- pDup = sqlite3ExprDup(db, pExpr, 0);
- if( db->mallocFailed ){
- sqlite3ExprDelete(db, pDup);
- return;
- }
- idxNew = whereClauseInsert(pWC, pDup, TERM_VIRTUAL|TERM_DYNAMIC);
- if( idxNew==0 ) return;
- pNew = &pWC->a[idxNew];
- pNew->iParent = idxTerm;
- pTerm = &pWC->a[idxTerm];
- pTerm->nChild = 1;
- pTerm->wtFlags |= TERM_COPIED;
- }else{
- pDup = pExpr;
- pNew = pTerm;
- }
- exprCommute(pParse, pDup);
- pLeft = pDup->pLeft;
- pNew->leftCursor = pLeft->iTable;
- pNew->u.leftColumn = pLeft->iColumn;
- pNew->prereqRight = prereqLeft;
- pNew->prereqAll = prereqAll;
- pNew->eOperator = operatorMask(pDup->op);
- }
- }
-
-#ifndef SQLITE_OMIT_BETWEEN_OPTIMIZATION
- /* If a term is the BETWEEN operator, create two new virtual terms
- ** that define the range that the BETWEEN implements. For example:
- **
- ** a BETWEEN b AND c
- **
- ** is converted into:
- **
- ** (a BETWEEN b AND c) AND (a>=b) AND (a<=c)
- **
- ** The two new terms are added onto the end of the WhereClause object.
- ** The new terms are "dynamic" and are children of the original BETWEEN
- ** term. That means that if the BETWEEN term is coded, the children are
- ** skipped. Or, if the children are satisfied by an index, the original
- ** BETWEEN term is skipped.
- */
- else if( pExpr->op==TK_BETWEEN && pWC->op==TK_AND ){
- ExprList *pList = pExpr->x.pList;
- int i;
- static const u8 ops[] = {TK_GE, TK_LE};
- assert( pList!=0 );
- assert( pList->nExpr==2 );
- for(i=0; i<2; i++){
- Expr *pNewExpr;
- int idxNew;
- pNewExpr = sqlite3PExpr(pParse, ops[i],
- sqlite3ExprDup(db, pExpr->pLeft, 0),
- sqlite3ExprDup(db, pList->a[i].pExpr, 0), 0);
- idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC);
- testcase( idxNew==0 );
- exprAnalyze(pSrc, pWC, idxNew);
- pTerm = &pWC->a[idxTerm];
- pWC->a[idxNew].iParent = idxTerm;
- }
- pTerm->nChild = 2;
- }
-#endif /* SQLITE_OMIT_BETWEEN_OPTIMIZATION */
-
-#if !defined(SQLITE_OMIT_OR_OPTIMIZATION) && !defined(SQLITE_OMIT_SUBQUERY)
- /* Analyze a term that is composed of two or more subterms connected by
- ** an OR operator.
- */
- else if( pExpr->op==TK_OR ){
- assert( pWC->op==TK_AND );
- exprAnalyzeOrTerm(pSrc, pWC, idxTerm);
- pTerm = &pWC->a[idxTerm];
- }
-#endif /* SQLITE_OMIT_OR_OPTIMIZATION */
-
-#ifndef SQLITE_OMIT_LIKE_OPTIMIZATION
- /* Add constraints to reduce the search space on a LIKE or GLOB
- ** operator.
- **
- ** A like pattern of the form "x LIKE 'abc%'" is changed into constraints
- **
- ** x>='abc' AND x<'abd' AND x LIKE 'abc%'
- **
- ** The last character of the prefix "abc" is incremented to form the
- ** termination condition "abd".
- */
- if( isLikeOrGlob(pParse, pExpr, &nPattern, &isComplete, &noCase)
- && pWC->op==TK_AND ){
- Expr *pLeft, *pRight;
- Expr *pStr1, *pStr2;
- Expr *pNewExpr1, *pNewExpr2;
- int idxNew1, idxNew2;
-
- pLeft = pExpr->x.pList->a[1].pExpr;
- pRight = pExpr->x.pList->a[0].pExpr;
- pStr1 = sqlite3Expr(db, TK_STRING, pRight->u.zToken);
- if( pStr1 ) pStr1->u.zToken[nPattern] = 0;
- pStr2 = sqlite3ExprDup(db, pStr1, 0);
- if( !db->mallocFailed ){
- u8 c, *pC; /* Last character before the first wildcard */
- pC = (u8*)&pStr2->u.zToken[nPattern-1];
- c = *pC;
- if( noCase ){
- /* The point is to increment the last character before the first
- ** wildcard. But if we increment '@', that will push it into the
- ** alphabetic range where case conversions will mess up the
- ** inequality. To avoid this, make sure to also run the full
- ** LIKE on all candidate expressions by clearing the isComplete flag
- */
- if( c=='A'-1 ) isComplete = 0;
-
- c = sqlite3UpperToLower[c];
- }
- *pC = c + 1;
- }
- pNewExpr1 = sqlite3PExpr(pParse, TK_GE, sqlite3ExprDup(db,pLeft,0),pStr1,0);
- idxNew1 = whereClauseInsert(pWC, pNewExpr1, TERM_VIRTUAL|TERM_DYNAMIC);
- testcase( idxNew1==0 );
- exprAnalyze(pSrc, pWC, idxNew1);
- pNewExpr2 = sqlite3PExpr(pParse, TK_LT, sqlite3ExprDup(db,pLeft,0),pStr2,0);
- idxNew2 = whereClauseInsert(pWC, pNewExpr2, TERM_VIRTUAL|TERM_DYNAMIC);
- testcase( idxNew2==0 );
- exprAnalyze(pSrc, pWC, idxNew2);
- pTerm = &pWC->a[idxTerm];
- if( isComplete ){
- pWC->a[idxNew1].iParent = idxTerm;
- pWC->a[idxNew2].iParent = idxTerm;
- pTerm->nChild = 2;
- }
- }
-#endif /* SQLITE_OMIT_LIKE_OPTIMIZATION */
-
-#ifndef SQLITE_OMIT_VIRTUALTABLE
- /* Add a WO_MATCH auxiliary term to the constraint set if the
- ** current expression is of the form: column MATCH expr.
- ** This information is used by the xBestIndex methods of
- ** virtual tables. The native query optimizer does not attempt
- ** to do anything with MATCH functions.
- */
- if( isMatchOfColumn(pExpr) ){
- int idxNew;
- Expr *pRight, *pLeft;
- WhereTerm *pNewTerm;
- Bitmask prereqColumn, prereqExpr;
-
- pRight = pExpr->x.pList->a[0].pExpr;
- pLeft = pExpr->x.pList->a[1].pExpr;
- prereqExpr = exprTableUsage(pMaskSet, pRight);
- prereqColumn = exprTableUsage(pMaskSet, pLeft);
- if( (prereqExpr & prereqColumn)==0 ){
- Expr *pNewExpr;
- pNewExpr = sqlite3PExpr(pParse, TK_MATCH,
- 0, sqlite3ExprDup(db, pRight, 0), 0);
- idxNew = whereClauseInsert(pWC, pNewExpr, TERM_VIRTUAL|TERM_DYNAMIC);
- testcase( idxNew==0 );
- pNewTerm = &pWC->a[idxNew];
- pNewTerm->prereqRight = prereqExpr;
- pNewTerm->leftCursor = pLeft->iTable;
- pNewTerm->u.leftColumn = pLeft->iColumn;
- pNewTerm->eOperator = WO_MATCH;
- pNewTerm->iParent = idxTerm;
- pTerm = &pWC->a[idxTerm];
- pTerm->nChild = 1;
- pTerm->wtFlags |= TERM_COPIED;
- pNewTerm->prereqAll = pTerm->prereqAll;
- }
- }
-#endif /* SQLITE_OMIT_VIRTUALTABLE */
-
- /* Prevent ON clause terms of a LEFT JOIN from being used to drive
- ** an index for tables to the left of the join.
- */
- pTerm->prereqRight |= extraRight;
-}
-
-/*
-** Return TRUE if any of the expressions in pList->a[iFirst...] contain
-** a reference to any table other than the iBase table.
-*/
-static int referencesOtherTables(
- ExprList *pList, /* Search expressions in ths list */
- WhereMaskSet *pMaskSet, /* Mapping from tables to bitmaps */
- int iFirst, /* Be searching with the iFirst-th expression */
- int iBase /* Ignore references to this table */
-){
- Bitmask allowed = ~getMask(pMaskSet, iBase);
- while( iFirst<pList->nExpr ){
- if( (exprTableUsage(pMaskSet, pList->a[iFirst++].pExpr)&allowed)!=0 ){
- return 1;
- }
- }
- return 0;
-}
-
-
-/*
-** This routine decides if pIdx can be used to satisfy the ORDER BY
-** clause. If it can, it returns 1. If pIdx cannot satisfy the
-** ORDER BY clause, this routine returns 0.
-**
-** pOrderBy is an ORDER BY clause from a SELECT statement. pTab is the
-** left-most table in the FROM clause of that same SELECT statement and
-** the table has a cursor number of "base". pIdx is an index on pTab.
-**
-** nEqCol is the number of columns of pIdx that are used as equality
-** constraints. Any of these columns may be missing from the ORDER BY
-** clause and the match can still be a success.
-**
-** All terms of the ORDER BY that match against the index must be either
-** ASC or DESC. (Terms of the ORDER BY clause past the end of a UNIQUE
-** index do not need to satisfy this constraint.) The *pbRev value is
-** set to 1 if the ORDER BY clause is all DESC and it is set to 0 if
-** the ORDER BY clause is all ASC.
-*/
-static int isSortingIndex(
- Parse *pParse, /* Parsing context */
- WhereMaskSet *pMaskSet, /* Mapping from table cursor numbers to bitmaps */
- Index *pIdx, /* The index we are testing */
- int base, /* Cursor number for the table to be sorted */
- ExprList *pOrderBy, /* The ORDER BY clause */
- int nEqCol, /* Number of index columns with == constraints */
- int *pbRev /* Set to 1 if ORDER BY is DESC */
-){
- int i, j; /* Loop counters */
- int sortOrder = 0; /* XOR of index and ORDER BY sort direction */
- int nTerm; /* Number of ORDER BY terms */
- struct ExprList_item *pTerm; /* A term of the ORDER BY clause */
- sqlite3 *db = pParse->db;
-
- assert( pOrderBy!=0 );
- nTerm = pOrderBy->nExpr;
- assert( nTerm>0 );
-
- /* Argument pIdx must either point to a 'real' named index structure,
- ** or an index structure allocated on the stack by bestBtreeIndex() to
- ** represent the rowid index that is part of every table. */
- assert( pIdx->zName || (pIdx->nColumn==1 && pIdx->aiColumn[0]==-1) );
-
- /* Match terms of the ORDER BY clause against columns of
- ** the index.
- **
- ** Note that indices have pIdx->nColumn regular columns plus
- ** one additional column containing the rowid. The rowid column
- ** of the index is also allowed to match against the ORDER BY
- ** clause.
- */
- for(i=j=0, pTerm=pOrderBy->a; j<nTerm && i<=pIdx->nColumn; i++){
- Expr *pExpr; /* The expression of the ORDER BY pTerm */
- CollSeq *pColl; /* The collating sequence of pExpr */
- int termSortOrder; /* Sort order for this term */
- int iColumn; /* The i-th column of the index. -1 for rowid */
- int iSortOrder; /* 1 for DESC, 0 for ASC on the i-th index term */
- const char *zColl; /* Name of the collating sequence for i-th index term */
-
- pExpr = pTerm->pExpr;
- if( pExpr->op!=TK_COLUMN || pExpr->iTable!=base ){
- /* Can not use an index sort on anything that is not a column in the
- ** left-most table of the FROM clause */
- break;
- }
- pColl = sqlite3ExprCollSeq(pParse, pExpr);
- if( !pColl ){
- pColl = db->pDfltColl;
- }
- if( pIdx->zName && i<pIdx->nColumn ){
- iColumn = pIdx->aiColumn[i];
- if( iColumn==pIdx->pTable->iPKey ){
- iColumn = -1;
- }
- iSortOrder = pIdx->aSortOrder[i];
- zColl = pIdx->azColl[i];
- }else{
- iColumn = -1;
- iSortOrder = 0;
- zColl = pColl->zName;
- }
- if( pExpr->iColumn!=iColumn || sqlite3StrICmp(pColl->zName, zColl) ){
- /* Term j of the ORDER BY clause does not match column i of the index */
- if( i<nEqCol ){
- /* If an index column that is constrained by == fails to match an
- ** ORDER BY term, that is OK. Just ignore that column of the index
- */
- continue;
- }else if( i==pIdx->nColumn ){
- /* Index column i is the rowid. All other terms match. */
- break;
- }else{
- /* If an index column fails to match and is not constrained by ==
- ** then the index cannot satisfy the ORDER BY constraint.
- */
- return 0;
- }
- }
- assert( pIdx->aSortOrder!=0 || iColumn==-1 );
- assert( pTerm->sortOrder==0 || pTerm->sortOrder==1 );
- assert( iSortOrder==0 || iSortOrder==1 );
- termSortOrder = iSortOrder ^ pTerm->sortOrder;
- if( i>nEqCol ){
- if( termSortOrder!=sortOrder ){
- /* Indices can only be used if all ORDER BY terms past the
- ** equality constraints are all either DESC or ASC. */
- return 0;
- }
- }else{
- sortOrder = termSortOrder;
- }
- j++;
- pTerm++;
- if( iColumn<0 && !referencesOtherTables(pOrderBy, pMaskSet, j, base) ){
- /* If the indexed column is the primary key and everything matches
- ** so far and none of the ORDER BY terms to the right reference other
- ** tables in the join, then we are assured that the index can be used
- ** to sort because the primary key is unique and so none of the other
- ** columns will make any difference
- */
- j = nTerm;
- }
- }
-
- *pbRev = sortOrder!=0;
- if( j>=nTerm ){
- /* All terms of the ORDER BY clause are covered by this index so
- ** this index can be used for sorting. */
- return 1;
- }
- if( pIdx->onError!=OE_None && i==pIdx->nColumn
- && !referencesOtherTables(pOrderBy, pMaskSet, j, base) ){
- /* All terms of this index match some prefix of the ORDER BY clause
- ** and the index is UNIQUE and no terms on the tail of the ORDER BY
- ** clause reference other tables in a join. If this is all true then
- ** the order by clause is superfluous. */
- return 1;
- }
- return 0;
-}
-
-/*
-** Prepare a crude estimate of the logarithm of the input value.
-** The results need not be exact. This is only used for estimating
-** the total cost of performing operations with O(logN) or O(NlogN)
-** complexity. Because N is just a guess, it is no great tragedy if
-** logN is a little off.
-*/
-static double estLog(double N){
- double logN = 1;
- double x = 10;
- while( N>x ){
- logN += 1;
- x *= 10;
- }
- return logN;
-}
-
-/*
-** Two routines for printing the content of an sqlite3_index_info
-** structure. Used for testing and debugging only. If neither
-** SQLITE_TEST or SQLITE_DEBUG are defined, then these routines
-** are no-ops.
-*/
-#if !defined(SQLITE_OMIT_VIRTUALTABLE) && defined(SQLITE_DEBUG)
-static void TRACE_IDX_INPUTS(sqlite3_index_info *p){
- int i;
- if( !sqlite3WhereTrace ) return;
- for(i=0; i<p->nConstraint; i++){
- sqlite3DebugPrintf(" constraint[%d]: col=%d termid=%d op=%d usabled=%d\n",
- i,
- p->aConstraint[i].iColumn,
- p->aConstraint[i].iTermOffset,
- p->aConstraint[i].op,
- p->aConstraint[i].usable);
- }
- for(i=0; i<p->nOrderBy; i++){
- sqlite3DebugPrintf(" orderby[%d]: col=%d desc=%d\n",
- i,
- p->aOrderBy[i].iColumn,
- p->aOrderBy[i].desc);
- }
-}
-static void TRACE_IDX_OUTPUTS(sqlite3_index_info *p){
- int i;
- if( !sqlite3WhereTrace ) return;
- for(i=0; i<p->nConstraint; i++){
- sqlite3DebugPrintf(" usage[%d]: argvIdx=%d omit=%d\n",
- i,
- p->aConstraintUsage[i].argvIndex,
- p->aConstraintUsage[i].omit);
- }
- sqlite3DebugPrintf(" idxNum=%d\n", p->idxNum);
- sqlite3DebugPrintf(" idxStr=%s\n", p->idxStr);
- sqlite3DebugPrintf(" orderByConsumed=%d\n", p->orderByConsumed);
- sqlite3DebugPrintf(" estimatedCost=%g\n", p->estimatedCost);
-}
-#else
-#define TRACE_IDX_INPUTS(A)
-#define TRACE_IDX_OUTPUTS(A)
-#endif
-
-/*
-** Required because bestIndex() is called by bestOrClauseIndex()
-*/
-static void bestIndex(
- Parse*, WhereClause*, struct SrcList_item*, Bitmask, ExprList*, WhereCost*);
-
-/*
-** This routine attempts to find an scanning strategy that can be used
-** to optimize an 'OR' expression that is part of a WHERE clause.
-**
-** The table associated with FROM clause term pSrc may be either a
-** regular B-Tree table or a virtual table.
-*/
-static void bestOrClauseIndex(
- Parse *pParse, /* The parsing context */
- WhereClause *pWC, /* The WHERE clause */
- struct SrcList_item *pSrc, /* The FROM clause term to search */
- Bitmask notReady, /* Mask of cursors that are not available */
- ExprList *pOrderBy, /* The ORDER BY clause */
- WhereCost *pCost /* Lowest cost query plan */
-){
-#ifndef SQLITE_OMIT_OR_OPTIMIZATION
- const int iCur = pSrc->iCursor; /* The cursor of the table to be accessed */
- const Bitmask maskSrc = getMask(pWC->pMaskSet, iCur); /* Bitmask for pSrc */
- WhereTerm * const pWCEnd = &pWC->a[pWC->nTerm]; /* End of pWC->a[] */
- WhereTerm *pTerm; /* A single term of the WHERE clause */
-
- /* Search the WHERE clause terms for a usable WO_OR term. */
- for(pTerm=pWC->a; pTerm<pWCEnd; pTerm++){
- if( pTerm->eOperator==WO_OR
- && ((pTerm->prereqAll & ~maskSrc) & notReady)==0
- && (pTerm->u.pOrInfo->indexable & maskSrc)!=0
- ){
- WhereClause * const pOrWC = &pTerm->u.pOrInfo->wc;
- WhereTerm * const pOrWCEnd = &pOrWC->a[pOrWC->nTerm];
- WhereTerm *pOrTerm;
- int flags = WHERE_MULTI_OR;
- double rTotal = 0;
- double nRow = 0;
- Bitmask used = 0;
-
- for(pOrTerm=pOrWC->a; pOrTerm<pOrWCEnd; pOrTerm++){
- WhereCost sTermCost;
- WHERETRACE(("... Multi-index OR testing for term %d of %d....\n",
- (pOrTerm - pOrWC->a), (pTerm - pWC->a)
- ));
- if( pOrTerm->eOperator==WO_AND ){
- WhereClause *pAndWC = &pOrTerm->u.pAndInfo->wc;
- bestIndex(pParse, pAndWC, pSrc, notReady, 0, &sTermCost);
- }else if( pOrTerm->leftCursor==iCur ){
- WhereClause tempWC;
- tempWC.pParse = pWC->pParse;
- tempWC.pMaskSet = pWC->pMaskSet;
- tempWC.op = TK_AND;
- tempWC.a = pOrTerm;
- tempWC.nTerm = 1;
- bestIndex(pParse, &tempWC, pSrc, notReady, 0, &sTermCost);
- }else{
- continue;
- }
- rTotal += sTermCost.rCost;
- nRow += sTermCost.nRow;
- used |= sTermCost.used;
- if( rTotal>=pCost->rCost ) break;
- }
-
- /* If there is an ORDER BY clause, increase the scan cost to account
- ** for the cost of the sort. */
- if( pOrderBy!=0 ){
- rTotal += nRow*estLog(nRow);
- WHERETRACE(("... sorting increases OR cost to %.9g\n", rTotal));
- }
-
- /* If the cost of scanning using this OR term for optimization is
- ** less than the current cost stored in pCost, replace the contents
- ** of pCost. */
- WHERETRACE(("... multi-index OR cost=%.9g nrow=%.9g\n", rTotal, nRow));
- if( rTotal<pCost->rCost ){
- pCost->rCost = rTotal;
- pCost->nRow = nRow;
- pCost->used = used;
- pCost->plan.wsFlags = flags;
- pCost->plan.u.pTerm = pTerm;
- }
- }
- }
-#endif /* SQLITE_OMIT_OR_OPTIMIZATION */
-}
-
-#ifndef SQLITE_OMIT_VIRTUALTABLE
-/*
-** Allocate and populate an sqlite3_index_info structure. It is the
-** responsibility of the caller to eventually release the structure
-** by passing the pointer returned by this function to sqlite3_free().
-*/
-static sqlite3_index_info *allocateIndexInfo(
- Parse *pParse,
- WhereClause *pWC,
- struct SrcList_item *pSrc,
- ExprList *pOrderBy
-){
- int i, j;
- int nTerm;
- struct sqlite3_index_constraint *pIdxCons;
- struct sqlite3_index_orderby *pIdxOrderBy;
- struct sqlite3_index_constraint_usage *pUsage;
- WhereTerm *pTerm;
- int nOrderBy;
- sqlite3_index_info *pIdxInfo;
-
- WHERETRACE(("Recomputing index info for %s...\n", pSrc->pTab->zName));
-
- /* Count the number of possible WHERE clause constraints referring
- ** to this virtual table */
- for(i=nTerm=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
- if( pTerm->leftCursor != pSrc->iCursor ) continue;
- assert( (pTerm->eOperator&(pTerm->eOperator-1))==0 );
- testcase( pTerm->eOperator==WO_IN );
- testcase( pTerm->eOperator==WO_ISNULL );
- if( pTerm->eOperator & (WO_IN|WO_ISNULL) ) continue;
- nTerm++;
- }
-
- /* If the ORDER BY clause contains only columns in the current
- ** virtual table then allocate space for the aOrderBy part of
- ** the sqlite3_index_info structure.
- */
- nOrderBy = 0;
- if( pOrderBy ){
- for(i=0; i<pOrderBy->nExpr; i++){
- Expr *pExpr = pOrderBy->a[i].pExpr;
- if( pExpr->op!=TK_COLUMN || pExpr->iTable!=pSrc->iCursor ) break;
- }
- if( i==pOrderBy->nExpr ){
- nOrderBy = pOrderBy->nExpr;
- }
- }
-
- /* Allocate the sqlite3_index_info structure
- */
- pIdxInfo = sqlite3DbMallocZero(pParse->db, sizeof(*pIdxInfo)
- + (sizeof(*pIdxCons) + sizeof(*pUsage))*nTerm
- + sizeof(*pIdxOrderBy)*nOrderBy );
- if( pIdxInfo==0 ){
- sqlite3ErrorMsg(pParse, "out of memory");
- /* (double)0 In case of SQLITE_OMIT_FLOATING_POINT... */
- return 0;
- }
-
- /* Initialize the structure. The sqlite3_index_info structure contains
- ** many fields that are declared "const" to prevent xBestIndex from
- ** changing them. We have to do some funky casting in order to
- ** initialize those fields.
- */
- pIdxCons = (struct sqlite3_index_constraint*)&pIdxInfo[1];
- pIdxOrderBy = (struct sqlite3_index_orderby*)&pIdxCons[nTerm];
- pUsage = (struct sqlite3_index_constraint_usage*)&pIdxOrderBy[nOrderBy];
- *(int*)&pIdxInfo->nConstraint = nTerm;
- *(int*)&pIdxInfo->nOrderBy = nOrderBy;
- *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint = pIdxCons;
- *(struct sqlite3_index_orderby**)&pIdxInfo->aOrderBy = pIdxOrderBy;
- *(struct sqlite3_index_constraint_usage**)&pIdxInfo->aConstraintUsage =
- pUsage;
-
- for(i=j=0, pTerm=pWC->a; i<pWC->nTerm; i++, pTerm++){
- if( pTerm->leftCursor != pSrc->iCursor ) continue;
- assert( (pTerm->eOperator&(pTerm->eOperator-1))==0 );
- testcase( pTerm->eOperator==WO_IN );
- testcase( pTerm->eOperator==WO_ISNULL );
- if( pTerm->eOperator & (WO_IN|WO_ISNULL) ) continue;
- pIdxCons[j].iColumn = pTerm->u.leftColumn;
- pIdxCons[j].iTermOffset = i;
- pIdxCons[j].op = (u8)pTerm->eOperator;
- /* The direct assignment in the previous line is possible only because
- ** the WO_ and SQLITE_INDEX_CONSTRAINT_ codes are identical. The
- ** following asserts verify this fact. */
- assert( WO_EQ==SQLITE_INDEX_CONSTRAINT_EQ );
- assert( WO_LT==SQLITE_INDEX_CONSTRAINT_LT );
- assert( WO_LE==SQLITE_INDEX_CONSTRAINT_LE );
- assert( WO_GT==SQLITE_INDEX_CONSTRAINT_GT );
- assert( WO_GE==SQLITE_INDEX_CONSTRAINT_GE );
- assert( WO_MATCH==SQLITE_INDEX_CONSTRAINT_MATCH );
- assert( pTerm->eOperator & (WO_EQ|WO_LT|WO_LE|WO_GT|WO_GE|WO_MATCH) );
- j++;
- }
- for(i=0; i<nOrderBy; i++){
- Expr *pExpr = pOrderBy->a[i].pExpr;
- pIdxOrderBy[i].iColumn = pExpr->iColumn;
- pIdxOrderBy[i].desc = pOrderBy->a[i].sortOrder;
- }
-
- return pIdxInfo;
-}
-
-/*
-** The table object reference passed as the second argument to this function
-** must represent a virtual table. This function invokes the xBestIndex()
-** method of the virtual table with the sqlite3_index_info pointer passed
-** as the argument.
-**
-** If an error occurs, pParse is populated with an error message and a
-** non-zero value is returned. Otherwise, 0 is returned and the output
-** part of the sqlite3_index_info structure is left populated.
-**
-** Whether or not an error is returned, it is the responsibility of the
-** caller to eventually free p->idxStr if p->needToFreeIdxStr indicates
-** that this is required.
-*/
-static int vtabBestIndex(Parse *pParse, Table *pTab, sqlite3_index_info *p){
- sqlite3_vtab *pVtab = sqlite3GetVTable(pParse->db, pTab)->pVtab;
- int i;
- int rc;
-
- (void)sqlite3SafetyOff(pParse->db);
- WHERETRACE(("xBestIndex for %s\n", pTab->zName));
- TRACE_IDX_INPUTS(p);
- rc = pVtab->pModule->xBestIndex(pVtab, p);
- TRACE_IDX_OUTPUTS(p);
- (void)sqlite3SafetyOn(pParse->db);
-
- if( rc!=SQLITE_OK ){
- if( rc==SQLITE_NOMEM ){
- pParse->db->mallocFailed = 1;
- }else if( !pVtab->zErrMsg ){
- sqlite3ErrorMsg(pParse, "%s", sqlite3ErrStr(rc));
- }else{
- sqlite3ErrorMsg(pParse, "%s", pVtab->zErrMsg);
- }
- }
- sqlite3DbFree(pParse->db, pVtab->zErrMsg);
- pVtab->zErrMsg = 0;
-
- for(i=0; i<p->nConstraint; i++){
- if( !p->aConstraint[i].usable && p->aConstraintUsage[i].argvIndex>0 ){
- sqlite3ErrorMsg(pParse,
- "table %s: xBestIndex returned an invalid plan", pTab->zName);
- }
- }
-
- return pParse->nErr;
-}
-
-
-/*
-** Compute the best index for a virtual table.
-**
-** The best index is computed by the xBestIndex method of the virtual
-** table module. This routine is really just a wrapper that sets up
-** the sqlite3_index_info structure that is used to communicate with
-** xBestIndex.
-**
-** In a join, this routine might be called multiple times for the
-** same virtual table. The sqlite3_index_info structure is created
-** and initialized on the first invocation and reused on all subsequent
-** invocations. The sqlite3_index_info structure is also used when
-** code is generated to access the virtual table. The whereInfoDelete()
-** routine takes care of freeing the sqlite3_index_info structure after
-** everybody has finished with it.
-*/
-static void bestVirtualIndex(
- Parse *pParse, /* The parsing context */
- WhereClause *pWC, /* The WHERE clause */
- struct SrcList_item *pSrc, /* The FROM clause term to search */
- Bitmask notReady, /* Mask of cursors that are not available */
- ExprList *pOrderBy, /* The order by clause */
- WhereCost *pCost, /* Lowest cost query plan */
- sqlite3_index_info **ppIdxInfo /* Index information passed to xBestIndex */
-){
- Table *pTab = pSrc->pTab;
- sqlite3_index_info *pIdxInfo;
- struct sqlite3_index_constraint *pIdxCons;
- struct sqlite3_index_constraint_usage *pUsage;
- WhereTerm *pTerm;
- int i, j;
- int nOrderBy;
-
- /* Make sure wsFlags is initialized to some sane value. Otherwise, if the
- ** malloc in allocateIndexInfo() fails and this function returns leaving
- ** wsFlags in an uninitialized state, the caller may behave unpredictably.
- */
- memset(pCost, 0, sizeof(*pCost));
- pCost->plan.wsFlags = WHERE_VIRTUALTABLE;
-
- /* If the sqlite3_index_info structure has not been previously
- ** allocated and initialized, then allocate and initialize it now.
- */
- pIdxInfo = *ppIdxInfo;
- if( pIdxInfo==0 ){
- *ppIdxInfo = pIdxInfo = allocateIndexInfo(pParse, pWC, pSrc, pOrderBy);
- }
- if( pIdxInfo==0 ){
- return;
- }
-
- /* At this point, the sqlite3_index_info structure that pIdxInfo points
- ** to will have been initialized, either during the current invocation or
- ** during some prior invocation. Now we just have to customize the
- ** details of pIdxInfo for the current invocation and pass it to
- ** xBestIndex.
- */
-
- /* The module name must be defined. Also, by this point there must
- ** be a pointer to an sqlite3_vtab structure. Otherwise
- ** sqlite3ViewGetColumnNames() would have picked up the error.
- */
- assert( pTab->azModuleArg && pTab->azModuleArg[0] );
- assert( sqlite3GetVTable(pParse->db, pTab) );
-
- /* Set the aConstraint[].usable fields and initialize all
- ** output variables to zero.
- **
- ** aConstraint[].usable is true for constraints where the right-hand
- ** side contains only references to tables to the left of the current
- ** table. In other words, if the constraint is of the form:
- **
- ** column = expr
- **
- ** and we are evaluating a join, then the constraint on column is
- ** only valid if all tables referenced in expr occur to the left
- ** of the table containing column.
- **
- ** The aConstraints[] array contains entries for all constraints
- ** on the current table. That way we only have to compute it once
- ** even though we might try to pick the best index multiple times.
- ** For each attempt at picking an index, the order of tables in the
- ** join might be different so we have to recompute the usable flag
- ** each time.
- */
- pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
- pUsage = pIdxInfo->aConstraintUsage;
- for(i=0; i<pIdxInfo->nConstraint; i++, pIdxCons++){
- j = pIdxCons->iTermOffset;
- pTerm = &pWC->a[j];
- pIdxCons->usable = (pTerm->prereqRight&notReady) ? 0 : 1;
- }
- memset(pUsage, 0, sizeof(pUsage[0])*pIdxInfo->nConstraint);
- if( pIdxInfo->needToFreeIdxStr ){
- sqlite3_free(pIdxInfo->idxStr);
- }
- pIdxInfo->idxStr = 0;
- pIdxInfo->idxNum = 0;
- pIdxInfo->needToFreeIdxStr = 0;
- pIdxInfo->orderByConsumed = 0;
- /* ((double)2) In case of SQLITE_OMIT_FLOATING_POINT... */
- pIdxInfo->estimatedCost = SQLITE_BIG_DBL / ((double)2);
- nOrderBy = pIdxInfo->nOrderBy;
- if( !pOrderBy ){
- pIdxInfo->nOrderBy = 0;
- }
-
- if( vtabBestIndex(pParse, pTab, pIdxInfo) ){
- return;
- }
-
- pIdxCons = *(struct sqlite3_index_constraint**)&pIdxInfo->aConstraint;
- for(i=0; i<pIdxInfo->nConstraint; i++){
- if( pUsage[i].argvIndex>0 ){
- pCost->used |= pWC->a[pIdxCons[i].iTermOffset].prereqRight;
- }
- }
-
- /* The cost is not allowed to be larger than SQLITE_BIG_DBL (the
- ** inital value of lowestCost in this loop. If it is, then the
- ** (cost<lowestCost) test below will never be true.
- **
- ** Use "(double)2" instead of "2.0" in case OMIT_FLOATING_POINT
- ** is defined.
- */
- if( (SQLITE_BIG_DBL/((double)2))<pIdxInfo->estimatedCost ){
- pCost->rCost = (SQLITE_BIG_DBL/((double)2));
- }else{
- pCost->rCost = pIdxInfo->estimatedCost;
- }
- pCost->plan.u.pVtabIdx = pIdxInfo;
- if( pIdxInfo->orderByConsumed ){
- pCost->plan.wsFlags |= WHERE_ORDERBY;
- }
- pCost->plan.nEq = 0;
- pIdxInfo->nOrderBy = nOrderBy;
-
- /* Try to find a more efficient access pattern by using multiple indexes
- ** to optimize an OR expression within the WHERE clause.
- */
- bestOrClauseIndex(pParse, pWC, pSrc, notReady, pOrderBy, pCost);
-}
-#endif /* SQLITE_OMIT_VIRTUALTABLE */
-
-/*
-** Argument pIdx is a pointer to an index structure that has an array of
-** SQLITE_INDEX_SAMPLES evenly spaced samples of the first indexed column
-** stored in Index.aSample. The domain of values stored in said column
-** may be thought of as divided into (SQLITE_INDEX_SAMPLES+1) regions.
-** Region 0 contains all values smaller than the first sample value. Region
-** 1 contains values larger than or equal to the value of the first sample,
-** but smaller than the value of the second. And so on.
-**
-** If successful, this function determines which of the regions value
-** pVal lies in, sets *piRegion to the region index (a value between 0
-** and SQLITE_INDEX_SAMPLES+1, inclusive) and returns SQLITE_OK.
-** Or, if an OOM occurs while converting text values between encodings,
-** SQLITE_NOMEM is returned and *piRegion is undefined.
-*/
-#ifdef SQLITE_ENABLE_STAT2
-static int whereRangeRegion(
- Parse *pParse, /* Database connection */
- Index *pIdx, /* Index to consider domain of */
- sqlite3_value *pVal, /* Value to consider */
- int *piRegion /* OUT: Region of domain in which value lies */
-){
- if( ALWAYS(pVal) ){
- IndexSample *aSample = pIdx->aSample;
- int i = 0;
- int eType = sqlite3_value_type(pVal);
-
- if( eType==SQLITE_INTEGER || eType==SQLITE_FLOAT ){
- double r = sqlite3_value_double(pVal);
- for(i=0; i<SQLITE_INDEX_SAMPLES; i++){
- if( aSample[i].eType==SQLITE_NULL ) continue;
- if( aSample[i].eType>=SQLITE_TEXT || aSample[i].u.r>r ) break;
- }
- }else{
- sqlite3 *db = pParse->db;
- CollSeq *pColl;
- const u8 *z;
- int n;
-
- /* pVal comes from sqlite3ValueFromExpr() so the type cannot be NULL */
- assert( eType==SQLITE_TEXT || eType==SQLITE_BLOB );
-
- if( eType==SQLITE_BLOB ){
- z = (const u8 *)sqlite3_value_blob(pVal);
- pColl = db->pDfltColl;
- assert( pColl->enc==SQLITE_UTF8 );
- }else{
- pColl = sqlite3GetCollSeq(db, SQLITE_UTF8, 0, *pIdx->azColl);
- if( pColl==0 ){
- sqlite3ErrorMsg(pParse, "no such collation sequence: %s",
- *pIdx->azColl);
- return SQLITE_ERROR;
- }
- z = (const u8 *)sqlite3ValueText(pVal, pColl->enc);
- if( !z ){
- return SQLITE_NOMEM;
- }
- assert( z && pColl && pColl->xCmp );
- }
- n = sqlite3ValueBytes(pVal, pColl->enc);
-
- for(i=0; i<SQLITE_INDEX_SAMPLES; i++){
- int r;
- int eSampletype = aSample[i].eType;
- if( eSampletype==SQLITE_NULL || eSampletype<eType ) continue;
- if( (eSampletype!=eType) ) break;
- if( pColl->enc==SQLITE_UTF8 ){
- r = pColl->xCmp(pColl->pUser, aSample[i].nByte, aSample[i].u.z, n, z);
- }else{
- int nSample;
- char *zSample = sqlite3Utf8to16(
- db, pColl->enc, aSample[i].u.z, aSample[i].nByte, &nSample
- );
- if( !zSample ){
- assert( db->mallocFailed );
- return SQLITE_NOMEM;
- }
- r = pColl->xCmp(pColl->pUser, nSample, zSample, n, z);
- sqlite3DbFree(db, zSample);
- }
- if( r>0 ) break;
- }
- }
-
- assert( i>=0 && i<=SQLITE_INDEX_SAMPLES );
- *piRegion = i;
- }
- return SQLITE_OK;
-}
-#endif /* #ifdef SQLITE_ENABLE_STAT2 */
-
-/*
-** This function is used to estimate the number of rows that will be visited
-** by scanning an index for a range of values. The range may have an upper
-** bound, a lower bound, or both. The WHERE clause terms that set the upper
-** and lower bounds are represented by pLower and pUpper respectively. For
-** example, assuming that index p is on t1(a):
-**
-** ... FROM t1 WHERE a > ? AND a < ? ...
-** |_____| |_____|
-** | |
-** pLower pUpper
-**
-** If either of the upper or lower bound is not present, then NULL is passed in
-** place of the corresponding WhereTerm.
-**
-** The nEq parameter is passed the index of the index column subject to the
-** range constraint. Or, equivalently, the number of equality constraints
-** optimized by the proposed index scan. For example, assuming index p is
-** on t1(a, b), and the SQL query is:
-**
-** ... FROM t1 WHERE a = ? AND b > ? AND b < ? ...
-**
-** then nEq should be passed the value 1 (as the range restricted column,
-** b, is the second left-most column of the index). Or, if the query is:
-**
-** ... FROM t1 WHERE a > ? AND a < ? ...
-**
-** then nEq should be passed 0.
-**
-** The returned value is an integer between 1 and 100, inclusive. A return
-** value of 1 indicates that the proposed range scan is expected to visit
-** approximately 1/100th (1%) of the rows selected by the nEq equality
-** constraints (if any). A return value of 100 indicates that it is expected
-** that the range scan will visit every row (100%) selected by the equality
-** constraints.
-**
-** In the absence of sqlite_stat2 ANALYZE data, each range inequality
-** reduces the search space by 2/3rds. Hence a single constraint (x>?)
-** results in a return of 33 and a range constraint (x>? AND x<?) results
-** in a return of 11.
-*/
-static int whereRangeScanEst(
- Parse *pParse, /* Parsing & code generating context */
- Index *p, /* The index containing the range-compared column; "x" */
- int nEq, /* index into p->aCol[] of the range-compared column */
- WhereTerm *pLower, /* Lower bound on the range. ex: "x>123" Might be NULL */
- WhereTerm *pUpper, /* Upper bound on the range. ex: "x<455" Might be NULL */
- int *piEst /* OUT: Return value */
-){
- int rc = SQLITE_OK;
-
-#ifdef SQLITE_ENABLE_STAT2
- sqlite3 *db = pParse->db;
- sqlite3_value *pLowerVal = 0;
- sqlite3_value *pUpperVal = 0;
-
- if( nEq==0 && p->aSample ){
- int iEst;
- int iLower = 0;
- int iUpper = SQLITE_INDEX_SAMPLES;
- u8 aff = p->pTable->aCol[0].affinity;
-
- if( pLower ){
- Expr *pExpr = pLower->pExpr->pRight;
- rc = sqlite3ValueFromExpr(db, pExpr, SQLITE_UTF8, aff, &pLowerVal);
- }
- if( rc==SQLITE_OK && pUpper ){
- Expr *pExpr = pUpper->pExpr->pRight;
- rc = sqlite3ValueFromExpr(db, pExpr, SQLITE_UTF8, aff, &pUpperVal);
- }
-
- if( rc!=SQLITE_OK || (pLowerVal==0 && pUpperVal==0) ){
- sqlite3ValueFree(pLowerVal);
- sqlite3ValueFree(pUpperVal);
- goto range_est_fallback;
- }else if( pLowerVal==0 ){
- rc = whereRangeRegion(pParse, p, pUpperVal, &iUpper);
- if( pLower ) iLower = iUpper/2;
- }else if( pUpperVal==0 ){
- rc = whereRangeRegion(pParse, p, pLowerVal, &iLower);
- if( pUpper ) iUpper = (iLower + SQLITE_INDEX_SAMPLES + 1)/2;
- }else{
- rc = whereRangeRegion(pParse, p, pUpperVal, &iUpper);
- if( rc==SQLITE_OK ){
- rc = whereRangeRegion(pParse, p, pLowerVal, &iLower);
- }
- }
-
- iEst = iUpper - iLower;
- testcase( iEst==SQLITE_INDEX_SAMPLES );
- assert( iEst<=SQLITE_INDEX_SAMPLES );
- if( iEst<1 ){
- iEst = 1;
- }
-
- sqlite3ValueFree(pLowerVal);
- sqlite3ValueFree(pUpperVal);
- *piEst = (iEst * 100)/SQLITE_INDEX_SAMPLES;
- return rc;
- }
-range_est_fallback:
-#else
- UNUSED_PARAMETER(pParse);
- UNUSED_PARAMETER(p);
- UNUSED_PARAMETER(nEq);
-#endif
- assert( pLower || pUpper );
- if( pLower && pUpper ){
- *piEst = 11;
- }else{
- *piEst = 33;
- }
- return rc;
-}
-
-
-/*
-** Find the query plan for accessing a particular table. Write the
-** best query plan and its cost into the WhereCost object supplied as the
-** last parameter.
-**
-** The lowest cost plan wins. The cost is an estimate of the amount of
-** CPU and disk I/O need to process the request using the selected plan.
-** Factors that influence cost include:
-**
-** * The estimated number of rows that will be retrieved. (The
-** fewer the better.)
-**
-** * Whether or not sorting must occur.
-**
-** * Whether or not there must be separate lookups in the
-** index and in the main table.
-**
-** If there was an INDEXED BY clause (pSrc->pIndex) attached to the table in
-** the SQL statement, then this function only considers plans using the
-** named index. If no such plan is found, then the returned cost is
-** SQLITE_BIG_DBL. If a plan is found that uses the named index,
-** then the cost is calculated in the usual way.
-**
-** If a NOT INDEXED clause (pSrc->notIndexed!=0) was attached to the table
-** in the SELECT statement, then no indexes are considered. However, the
-** selected plan may still take advantage of the tables built-in rowid
-** index.
-*/
-static void bestBtreeIndex(
- Parse *pParse, /* The parsing context */
- WhereClause *pWC, /* The WHERE clause */
- struct SrcList_item *pSrc, /* The FROM clause term to search */
- Bitmask notReady, /* Mask of cursors that are not available */
- ExprList *pOrderBy, /* The ORDER BY clause */
- WhereCost *pCost /* Lowest cost query plan */
-){
- int iCur = pSrc->iCursor; /* The cursor of the table to be accessed */
- Index *pProbe; /* An index we are evaluating */
- Index *pIdx; /* Copy of pProbe, or zero for IPK index */
- int eqTermMask; /* Current mask of valid equality operators */
- int idxEqTermMask; /* Index mask of valid equality operators */
- Index sPk; /* A fake index object for the primary key */
- unsigned int aiRowEstPk[2]; /* The aiRowEst[] value for the sPk index */
- int aiColumnPk = -1; /* The aColumn[] value for the sPk index */
- int wsFlagMask; /* Allowed flags in pCost->plan.wsFlag */
-
- /* Initialize the cost to a worst-case value */
- memset(pCost, 0, sizeof(*pCost));
- pCost->rCost = SQLITE_BIG_DBL;
-
- /* If the pSrc table is the right table of a LEFT JOIN then we may not
- ** use an index to satisfy IS NULL constraints on that table. This is
- ** because columns might end up being NULL if the table does not match -
- ** a circumstance which the index cannot help us discover. Ticket #2177.
- */
- if( pSrc->jointype & JT_LEFT ){
- idxEqTermMask = WO_EQ|WO_IN;
- }else{
- idxEqTermMask = WO_EQ|WO_IN|WO_ISNULL;
- }
-
- if( pSrc->pIndex ){
- /* An INDEXED BY clause specifies a particular index to use */
- pIdx = pProbe = pSrc->pIndex;
- wsFlagMask = ~(WHERE_ROWID_EQ|WHERE_ROWID_RANGE);
- eqTermMask = idxEqTermMask;
- }else{
- /* There is no INDEXED BY clause. Create a fake Index object to
- ** represent the primary key */
- Index *pFirst; /* Any other index on the table */
- memset(&sPk, 0, sizeof(Index));
- sPk.nColumn = 1;
- sPk.aiColumn = &aiColumnPk;
- sPk.aiRowEst = aiRowEstPk;
- aiRowEstPk[1] = 1;
- sPk.onError = OE_Replace;
- sPk.pTable = pSrc->pTab;
- pFirst = pSrc->pTab->pIndex;
- if( pSrc->notIndexed==0 ){
- sPk.pNext = pFirst;
- }
- /* The aiRowEstPk[0] is an estimate of the total number of rows in the
- ** table. Get this information from the ANALYZE information if it is
- ** available. If not available, assume the table 1 million rows in size.
- */
- if( pFirst ){
- assert( pFirst->aiRowEst!=0 ); /* Allocated together with pFirst */
- aiRowEstPk[0] = pFirst->aiRowEst[0];
- }else{
- aiRowEstPk[0] = 1000000;
- }
- pProbe = &sPk;
- wsFlagMask = ~(
- WHERE_COLUMN_IN|WHERE_COLUMN_EQ|WHERE_COLUMN_NULL|WHERE_COLUMN_RANGE
- );
- eqTermMask = WO_EQ|WO_IN;
- pIdx = 0;
- }
-
- /* Loop over all indices looking for the best one to use
- */
- for(; pProbe; pIdx=pProbe=pProbe->pNext){
- const unsigned int * const aiRowEst = pProbe->aiRowEst;
- double cost; /* Cost of using pProbe */
- double nRow; /* Estimated number of rows in result set */
- int rev; /* True to scan in reverse order */
- int wsFlags = 0;
- Bitmask used = 0;
-
- /* The following variables are populated based on the properties of
- ** scan being evaluated. They are then used to determine the expected
- ** cost and number of rows returned.
- **
- ** nEq:
- ** Number of equality terms that can be implemented using the index.
- **
- ** nInMul:
- ** The "in-multiplier". This is an estimate of how many seek operations
- ** SQLite must perform on the index in question. For example, if the
- ** WHERE clause is:
- **
- ** WHERE a IN (1, 2, 3) AND b IN (4, 5, 6)
- **
- ** SQLite must perform 9 lookups on an index on (a, b), so nInMul is
- ** set to 9. Given the same schema and either of the following WHERE
- ** clauses:
- **
- ** WHERE a = 1
- ** WHERE a >= 2
- **
- ** nInMul is set to 1.
- **
- ** If there exists a WHERE term of the form "x IN (SELECT ...)", then
- ** the sub-select is assumed to return 25 rows for the purposes of
- ** determining nInMul.
- **
- ** bInEst:
- ** Set to true if there was at least one "x IN (SELECT ...)" term used
- ** in determining the value of nInMul.
- **
- ** nBound:
- ** An estimate on the amount of the table that must be searched. A
- ** value of 100 means the entire table is searched. Range constraints
- ** might reduce this to a value less than 100 to indicate that only
- ** a fraction of the table needs searching. In the absence of
- ** sqlite_stat2 ANALYZE data, a single inequality reduces the search
- ** space to 1/3rd its original size. So an x>? constraint reduces
- ** nBound to 33. Two constraints (x>? AND x<?) reduce nBound to 11.
- **
- ** bSort:
- ** Boolean. True if there is an ORDER BY clause that will require an
- ** external sort (i.e. scanning the index being evaluated will not
- ** correctly order records).
- **
- ** bLookup:
- ** Boolean. True if for each index entry visited a lookup on the
- ** corresponding table b-tree is required. This is always false
- ** for the rowid index. For other indexes, it is true unless all the
- ** columns of the table used by the SELECT statement are present in
- ** the index (such an index is sometimes described as a covering index).
- ** For example, given the index on (a, b), the second of the following
- ** two queries requires table b-tree lookups, but the first does not.
- **
- ** SELECT a, b FROM tbl WHERE a = 1;
- ** SELECT a, b, c FROM tbl WHERE a = 1;
- */
- int nEq;
- int bInEst = 0;
- int nInMul = 1;
- int nBound = 100;
- int bSort = 0;
- int bLookup = 0;
-
- /* Determine the values of nEq and nInMul */
- for(nEq=0; nEq<pProbe->nColumn; nEq++){
- WhereTerm *pTerm; /* A single term of the WHERE clause */
- int j = pProbe->aiColumn[nEq];
- pTerm = findTerm(pWC, iCur, j, notReady, eqTermMask, pIdx);
- if( pTerm==0 ) break;
- wsFlags |= (WHERE_COLUMN_EQ|WHERE_ROWID_EQ);
- if( pTerm->eOperator & WO_IN ){
- Expr *pExpr = pTerm->pExpr;
- wsFlags |= WHERE_COLUMN_IN;
- if( ExprHasProperty(pExpr, EP_xIsSelect) ){
- nInMul *= 25;
- bInEst = 1;
- }else if( pExpr->x.pList ){
- nInMul *= pExpr->x.pList->nExpr + 1;
- }
- }else if( pTerm->eOperator & WO_ISNULL ){
- wsFlags |= WHERE_COLUMN_NULL;
- }
- used |= pTerm->prereqRight;
- }
-
- /* Determine the value of nBound. */
- if( nEq<pProbe->nColumn ){
- int j = pProbe->aiColumn[nEq];
- if( findTerm(pWC, iCur, j, notReady, WO_LT|WO_LE|WO_GT|WO_GE, pIdx) ){
- WhereTerm *pTop = findTerm(pWC, iCur, j, notReady, WO_LT|WO_LE, pIdx);
- WhereTerm *pBtm = findTerm(pWC, iCur, j, notReady, WO_GT|WO_GE, pIdx);
- whereRangeScanEst(pParse, pProbe, nEq, pBtm, pTop, &nBound);
- if( pTop ){
- wsFlags |= WHERE_TOP_LIMIT;
- used |= pTop->prereqRight;
- }
- if( pBtm ){
- wsFlags |= WHERE_BTM_LIMIT;
- used |= pBtm->prereqRight;
- }
- wsFlags |= (WHERE_COLUMN_RANGE|WHERE_ROWID_RANGE);
- }
- }else if( pProbe->onError!=OE_None ){
- testcase( wsFlags & WHERE_COLUMN_IN );
- testcase( wsFlags & WHERE_COLUMN_NULL );
- if( (wsFlags & (WHERE_COLUMN_IN|WHERE_COLUMN_NULL))==0 ){
- wsFlags |= WHERE_UNIQUE;
- }
- }
-
- /* If there is an ORDER BY clause and the index being considered will
- ** naturally scan rows in the required order, set the appropriate flags
- ** in wsFlags. Otherwise, if there is an ORDER BY clause but the index
- ** will scan rows in a different order, set the bSort variable. */
- if( pOrderBy ){
- if( (wsFlags & (WHERE_COLUMN_IN|WHERE_COLUMN_NULL))==0
- && isSortingIndex(pParse,pWC->pMaskSet,pProbe,iCur,pOrderBy,nEq,&rev)
- ){
- wsFlags |= WHERE_ROWID_RANGE|WHERE_COLUMN_RANGE|WHERE_ORDERBY;
- wsFlags |= (rev ? WHERE_REVERSE : 0);
- }else{
- bSort = 1;
- }
- }
-
- /* If currently calculating the cost of using an index (not the IPK
- ** index), determine if all required column data may be obtained without
- ** seeking to entries in the main table (i.e. if the index is a covering
- ** index for this query). If it is, set the WHERE_IDX_ONLY flag in
- ** wsFlags. Otherwise, set the bLookup variable to true. */
- if( pIdx && wsFlags ){
- Bitmask m = pSrc->colUsed;
- int j;
- for(j=0; j<pIdx->nColumn; j++){
- int x = pIdx->aiColumn[j];
- if( x<BMS-1 ){
- m &= ~(((Bitmask)1)<<x);
- }
- }
- if( m==0 ){
- wsFlags |= WHERE_IDX_ONLY;
- }else{
- bLookup = 1;
- }
- }
-
- /**** Begin adding up the cost of using this index (Needs improvements)
- **
- ** Estimate the number of rows of output. For an IN operator,
- ** do not let the estimate exceed half the rows in the table.
- */
- nRow = (double)(aiRowEst[nEq] * nInMul);
- if( bInEst && nRow*2>aiRowEst[0] ){
- nRow = aiRowEst[0]/2;
- nInMul = (int)(nRow / aiRowEst[nEq]);
- }
-
- /* Assume constant cost to access a row and logarithmic cost to
- ** do a binary search. Hence, the initial cost is the number of output
- ** rows plus log2(table-size) times the number of binary searches.
- */
- cost = nRow + nInMul*estLog(aiRowEst[0]);
-
- /* Adjust the number of rows and the cost downward to reflect rows
- ** that are excluded by range constraints.
- */
- nRow = (nRow * (double)nBound) / (double)100;
- cost = (cost * (double)nBound) / (double)100;
-
- /* Add in the estimated cost of sorting the result
- */
- if( bSort ){
- cost += cost*estLog(cost);
- }
-
- /* If all information can be taken directly from the index, we avoid
- ** doing table lookups. This reduces the cost by half. (Not really -
- ** this needs to be fixed.)
- */
- if( pIdx && bLookup==0 ){
- cost /= (double)2;
- }
- /**** Cost of using this index has now been computed ****/
-
- WHERETRACE((
- "tbl=%s idx=%s nEq=%d nInMul=%d nBound=%d bSort=%d bLookup=%d"
- " wsFlags=%d (nRow=%.2f cost=%.2f)\n",
- pSrc->pTab->zName, (pIdx ? pIdx->zName : "ipk"),
- nEq, nInMul, nBound, bSort, bLookup, wsFlags, nRow, cost
- ));
-
- /* If this index is the best we have seen so far, then record this
- ** index and its cost in the pCost structure.
- */
- if( (!pIdx || wsFlags) && cost<pCost->rCost ){
- pCost->rCost = cost;
- pCost->nRow = nRow;
- pCost->used = used;
- pCost->plan.wsFlags = (wsFlags&wsFlagMask);
- pCost->plan.nEq = nEq;
- pCost->plan.u.pIdx = pIdx;
- }
-
- /* If there was an INDEXED BY clause, then only that one index is
- ** considered. */
- if( pSrc->pIndex ) break;
-
- /* Reset masks for the next index in the loop */
- wsFlagMask = ~(WHERE_ROWID_EQ|WHERE_ROWID_RANGE);
- eqTermMask = idxEqTermMask;
- }
-
- /* If there is no ORDER BY clause and the SQLITE_ReverseOrder flag
- ** is set, then reverse the order that the index will be scanned
- ** in. This is used for application testing, to help find cases
- ** where application behaviour depends on the (undefined) order that
- ** SQLite outputs rows in in the absence of an ORDER BY clause. */
- if( !pOrderBy && pParse->db->flags & SQLITE_ReverseOrder ){
- pCost->plan.wsFlags |= WHERE_REVERSE;
- }
-
- assert( pOrderBy || (pCost->plan.wsFlags&WHERE_ORDERBY)==0 );
- assert( pCost->plan.u.pIdx==0 || (pCost->plan.wsFlags&WHERE_ROWID_EQ)==0 );
- assert( pSrc->pIndex==0
- || pCost->plan.u.pIdx==0
- || pCost->plan.u.pIdx==pSrc->pIndex
- );
-
- WHERETRACE(("best index is: %s\n",
- (pCost->plan.u.pIdx ? pCost->plan.u.pIdx->zName : "ipk")
- ));
-
- bestOrClauseIndex(pParse, pWC, pSrc, notReady, pOrderBy, pCost);
- pCost->plan.wsFlags |= eqTermMask;
-}
-
-/*
-** Find the query plan for accessing table pSrc->pTab. Write the
-** best query plan and its cost into the WhereCost object supplied
-** as the last parameter. This function may calculate the cost of
-** both real and virtual table scans.
-*/
-static void bestIndex(
- Parse *pParse, /* The parsing context */
- WhereClause *pWC, /* The WHERE clause */
- struct SrcList_item *pSrc, /* The FROM clause term to search */
- Bitmask notReady, /* Mask of cursors that are not available */
- ExprList *pOrderBy, /* The ORDER BY clause */
- WhereCost *pCost /* Lowest cost query plan */
-){
-#ifndef SQLITE_OMIT_VIRTUALTABLE
- if( IsVirtual(pSrc->pTab) ){
- sqlite3_index_info *p = 0;
- bestVirtualIndex(pParse, pWC, pSrc, notReady, pOrderBy, pCost, &p);
- if( p->needToFreeIdxStr ){
- sqlite3_free(p->idxStr);
- }
- sqlite3DbFree(pParse->db, p);
- }else
-#endif
- {
- bestBtreeIndex(pParse, pWC, pSrc, notReady, pOrderBy, pCost);
- }
-}
-
-/*
-** Disable a term in the WHERE clause. Except, do not disable the term
-** if it controls a LEFT OUTER JOIN and it did not originate in the ON
-** or USING clause of that join.
-**
-** Consider the term t2.z='ok' in the following queries:
-**
-** (1) SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x WHERE t2.z='ok'
-** (2) SELECT * FROM t1 LEFT JOIN t2 ON t1.a=t2.x AND t2.z='ok'
-** (3) SELECT * FROM t1, t2 WHERE t1.a=t2.x AND t2.z='ok'
-**
-** The t2.z='ok' is disabled in the in (2) because it originates
-** in the ON clause. The term is disabled in (3) because it is not part
-** of a LEFT OUTER JOIN. In (1), the term is not disabled.
-**
-** Disabling a term causes that term to not be tested in the inner loop
-** of the join. Disabling is an optimization. When terms are satisfied
-** by indices, we disable them to prevent redundant tests in the inner
-** loop. We would get the correct results if nothing were ever disabled,
-** but joins might run a little slower. The trick is to disable as much
-** as we can without disabling too much. If we disabled in (1), we'd get
-** the wrong answer. See ticket #813.
-*/
-static void disableTerm(WhereLevel *pLevel, WhereTerm *pTerm){
- if( pTerm
- && ALWAYS((pTerm->wtFlags & TERM_CODED)==0)
- && (pLevel->iLeftJoin==0 || ExprHasProperty(pTerm->pExpr, EP_FromJoin))
- ){
- pTerm->wtFlags |= TERM_CODED;
- if( pTerm->iParent>=0 ){
- WhereTerm *pOther = &pTerm->pWC->a[pTerm->iParent];
- if( (--pOther->nChild)==0 ){
- disableTerm(pLevel, pOther);
- }
- }
- }
-}
-
-/*
-** Code an OP_Affinity opcode to apply the column affinity string zAff
-** to the n registers starting at base.
-**
-** Buffer zAff was allocated using sqlite3DbMalloc(). It is the
-** responsibility of this function to arrange for it to be eventually
-** freed using sqlite3DbFree().
-*/
-static void codeApplyAffinity(Parse *pParse, int base, int n, char *zAff){
- Vdbe *v = pParse->pVdbe;
- assert( v!=0 );
- sqlite3VdbeAddOp2(v, OP_Affinity, base, n);
- sqlite3VdbeChangeP4(v, -1, zAff, P4_DYNAMIC);
- sqlite3ExprCacheAffinityChange(pParse, base, n);
-}
-
-
-/*
-** Generate code for a single equality term of the WHERE clause. An equality
-** term can be either X=expr or X IN (...). pTerm is the term to be
-** coded.
-**
-** The current value for the constraint is left in register iReg.
-**
-** For a constraint of the form X=expr, the expression is evaluated and its
-** result is left on the stack. For constraints of the form X IN (...)
-** this routine sets up a loop that will iterate over all values of X.
-*/
-static int codeEqualityTerm(
- Parse *pParse, /* The parsing context */
- WhereTerm *pTerm, /* The term of the WHERE clause to be coded */
- WhereLevel *pLevel, /* When level of the FROM clause we are working on */
- int iTarget /* Attempt to leave results in this register */
-){
- Expr *pX = pTerm->pExpr;
- Vdbe *v = pParse->pVdbe;
- int iReg; /* Register holding results */
-
- assert( iTarget>0 );
- if( pX->op==TK_EQ ){
- iReg = sqlite3ExprCodeTarget(pParse, pX->pRight, iTarget);
- }else if( pX->op==TK_ISNULL ){
- iReg = iTarget;
- sqlite3VdbeAddOp2(v, OP_Null, 0, iReg);
-#ifndef SQLITE_OMIT_SUBQUERY
- }else{
- int eType;
- int iTab;
- struct InLoop *pIn;
-
- assert( pX->op==TK_IN );
- iReg = iTarget;
- eType = sqlite3FindInIndex(pParse, pX, 0);
- iTab = pX->iTable;
- sqlite3VdbeAddOp2(v, OP_Rewind, iTab, 0);
- assert( pLevel->plan.wsFlags & WHERE_IN_ABLE );
- if( pLevel->u.in.nIn==0 ){
- pLevel->addrNxt = sqlite3VdbeMakeLabel(v);
- }
- pLevel->u.in.nIn++;
- pLevel->u.in.aInLoop =
- sqlite3DbReallocOrFree(pParse->db, pLevel->u.in.aInLoop,
- sizeof(pLevel->u.in.aInLoop[0])*pLevel->u.in.nIn);
- pIn = pLevel->u.in.aInLoop;
- if( pIn ){
- pIn += pLevel->u.in.nIn - 1;
- pIn->iCur = iTab;
- if( eType==IN_INDEX_ROWID ){
- pIn->addrInTop = sqlite3VdbeAddOp2(v, OP_Rowid, iTab, iReg);
- }else{
- pIn->addrInTop = sqlite3VdbeAddOp3(v, OP_Column, iTab, 0, iReg);
- }
- sqlite3VdbeAddOp1(v, OP_IsNull, iReg);
- }else{
- pLevel->u.in.nIn = 0;
- }
-#endif
- }
- disableTerm(pLevel, pTerm);
- return iReg;
-}
-
-/*
-** Generate code that will evaluate all == and IN constraints for an
-** index. The values for all constraints are left on the stack.
-**
-** For example, consider table t1(a,b,c,d,e,f) with index i1(a,b,c).
-** Suppose the WHERE clause is this: a==5 AND b IN (1,2,3) AND c>5 AND c<10
-** The index has as many as three equality constraints, but in this
-** example, the third "c" value is an inequality. So only two
-** constraints are coded. This routine will generate code to evaluate
-** a==5 and b IN (1,2,3). The current values for a and b will be stored
-** in consecutive registers and the index of the first register is returned.
-**
-** In the example above nEq==2. But this subroutine works for any value
-** of nEq including 0. If nEq==0, this routine is nearly a no-op.
-** The only thing it does is allocate the pLevel->iMem memory cell.
-**
-** This routine always allocates at least one memory cell and returns
-** the index of that memory cell. The code that
-** calls this routine will use that memory cell to store the termination
-** key value of the loop. If one or more IN operators appear, then
-** this routine allocates an additional nEq memory cells for internal
-** use.
-**
-** Before returning, *pzAff is set to point to a buffer containing a
-** copy of the column affinity string of the index allocated using
-** sqlite3DbMalloc(). Except, entries in the copy of the string associated
-** with equality constraints that use NONE affinity are set to
-** SQLITE_AFF_NONE. This is to deal with SQL such as the following:
-**
-** CREATE TABLE t1(a TEXT PRIMARY KEY, b);
-** SELECT ... FROM t1 AS t2, t1 WHERE t1.a = t2.b;
-**
-** In the example above, the index on t1(a) has TEXT affinity. But since
-** the right hand side of the equality constraint (t2.b) has NONE affinity,
-** no conversion should be attempted before using a t2.b value as part of
-** a key to search the index. Hence the first byte in the returned affinity
-** string in this example would be set to SQLITE_AFF_NONE.
-*/
-static int codeAllEqualityTerms(
- Parse *pParse, /* Parsing context */
- WhereLevel *pLevel, /* Which nested loop of the FROM we are coding */
- WhereClause *pWC, /* The WHERE clause */
- Bitmask notReady, /* Which parts of FROM have not yet been coded */
- int nExtraReg, /* Number of extra registers to allocate */
- char **pzAff /* OUT: Set to point to affinity string */
-){
- int nEq = pLevel->plan.nEq; /* The number of == or IN constraints to code */
- Vdbe *v = pParse->pVdbe; /* The vm under construction */
- Index *pIdx; /* The index being used for this loop */
- int iCur = pLevel->iTabCur; /* The cursor of the table */
- WhereTerm *pTerm; /* A single constraint term */
- int j; /* Loop counter */
- int regBase; /* Base register */
- int nReg; /* Number of registers to allocate */
- char *zAff; /* Affinity string to return */
-
- /* This module is only called on query plans that use an index. */
- assert( pLevel->plan.wsFlags & WHERE_INDEXED );
- pIdx = pLevel->plan.u.pIdx;
-
- /* Figure out how many memory cells we will need then allocate them.
- */
- regBase = pParse->nMem + 1;
- nReg = pLevel->plan.nEq + nExtraReg;
- pParse->nMem += nReg;
-
- zAff = sqlite3DbStrDup(pParse->db, sqlite3IndexAffinityStr(v, pIdx));
- if( !zAff ){
- pParse->db->mallocFailed = 1;
- }
-
- /* Evaluate the equality constraints
- */
- assert( pIdx->nColumn>=nEq );
- for(j=0; j<nEq; j++){
- int r1;
- int k = pIdx->aiColumn[j];
- pTerm = findTerm(pWC, iCur, k, notReady, pLevel->plan.wsFlags, pIdx);
- if( NEVER(pTerm==0) ) break;
- assert( (pTerm->wtFlags & TERM_CODED)==0 );
- r1 = codeEqualityTerm(pParse, pTerm, pLevel, regBase+j);
- if( r1!=regBase+j ){
- if( nReg==1 ){
- sqlite3ReleaseTempReg(pParse, regBase);
- regBase = r1;
- }else{
- sqlite3VdbeAddOp2(v, OP_SCopy, r1, regBase+j);
- }
- }
- testcase( pTerm->eOperator & WO_ISNULL );
- testcase( pTerm->eOperator & WO_IN );
- if( (pTerm->eOperator & (WO_ISNULL|WO_IN))==0 ){
- sqlite3VdbeAddOp2(v, OP_IsNull, regBase+j, pLevel->addrBrk);
- if( zAff
- && sqlite3CompareAffinity(pTerm->pExpr->pRight, zAff[j])==SQLITE_AFF_NONE
- ){
- zAff[j] = SQLITE_AFF_NONE;
- }
- }
- }
- *pzAff = zAff;
- return regBase;
-}
-
-/*
-** Generate code for the start of the iLevel-th loop in the WHERE clause
-** implementation described by pWInfo.
-*/
-static Bitmask codeOneLoopStart(
- WhereInfo *pWInfo, /* Complete information about the WHERE clause */
- int iLevel, /* Which level of pWInfo->a[] should be coded */
- u16 wctrlFlags, /* One of the WHERE_* flags defined in sqliteInt.h */
- Bitmask notReady /* Which tables are currently available */
-){
- int j, k; /* Loop counters */
- int iCur; /* The VDBE cursor for the table */
- int addrNxt; /* Where to jump to continue with the next IN case */
- int omitTable; /* True if we use the index only */
- int bRev; /* True if we need to scan in reverse order */
- WhereLevel *pLevel; /* The where level to be coded */
- WhereClause *pWC; /* Decomposition of the entire WHERE clause */
- WhereTerm *pTerm; /* A WHERE clause term */
- Parse *pParse; /* Parsing context */
- Vdbe *v; /* The prepared stmt under constructions */
- struct SrcList_item *pTabItem; /* FROM clause term being coded */
- int addrBrk; /* Jump here to break out of the loop */
- int addrCont; /* Jump here to continue with next cycle */
- int iRowidReg = 0; /* Rowid is stored in this register, if not zero */
- int iReleaseReg = 0; /* Temp register to free before returning */
-
- pParse = pWInfo->pParse;
- v = pParse->pVdbe;
- pWC = pWInfo->pWC;
- pLevel = &pWInfo->a[iLevel];
- pTabItem = &pWInfo->pTabList->a[pLevel->iFrom];
- iCur = pTabItem->iCursor;
- bRev = (pLevel->plan.wsFlags & WHERE_REVERSE)!=0;
- omitTable = (pLevel->plan.wsFlags & WHERE_IDX_ONLY)!=0
- && (wctrlFlags & WHERE_FORCE_TABLE)==0;
-
- /* Create labels for the "break" and "continue" instructions
- ** for the current loop. Jump to addrBrk to break out of a loop.
- ** Jump to cont to go immediately to the next iteration of the
- ** loop.
- **
- ** When there is an IN operator, we also have a "addrNxt" label that
- ** means to continue with the next IN value combination. When
- ** there are no IN operators in the constraints, the "addrNxt" label
- ** is the same as "addrBrk".
- */
- addrBrk = pLevel->addrBrk = pLevel->addrNxt = sqlite3VdbeMakeLabel(v);
- addrCont = pLevel->addrCont = sqlite3VdbeMakeLabel(v);
-
- /* If this is the right table of a LEFT OUTER JOIN, allocate and
- ** initialize a memory cell that records if this table matches any
- ** row of the left table of the join.
- */
- if( pLevel->iFrom>0 && (pTabItem[0].jointype & JT_LEFT)!=0 ){
- pLevel->iLeftJoin = ++pParse->nMem;
- sqlite3VdbeAddOp2(v, OP_Integer, 0, pLevel->iLeftJoin);
- VdbeComment((v, "init LEFT JOIN no-match flag"));
- }
-
-#ifndef SQLITE_OMIT_VIRTUALTABLE
- if( (pLevel->plan.wsFlags & WHERE_VIRTUALTABLE)!=0 ){
- /* Case 0: The table is a virtual-table. Use the VFilter and VNext
- ** to access the data.
- */
- int iReg; /* P3 Value for OP_VFilter */
- sqlite3_index_info *pVtabIdx = pLevel->plan.u.pVtabIdx;
- int nConstraint = pVtabIdx->nConstraint;
- struct sqlite3_index_constraint_usage *aUsage =
- pVtabIdx->aConstraintUsage;
- const struct sqlite3_index_constraint *aConstraint =
- pVtabIdx->aConstraint;
-
- iReg = sqlite3GetTempRange(pParse, nConstraint+2);
- for(j=1; j<=nConstraint; j++){
- for(k=0; k<nConstraint; k++){
- if( aUsage[k].argvIndex==j ){
- int iTerm = aConstraint[k].iTermOffset;
- sqlite3ExprCode(pParse, pWC->a[iTerm].pExpr->pRight, iReg+j+1);
- break;
- }
- }
- if( k==nConstraint ) break;
- }
- sqlite3VdbeAddOp2(v, OP_Integer, pVtabIdx->idxNum, iReg);
- sqlite3VdbeAddOp2(v, OP_Integer, j-1, iReg+1);
- sqlite3VdbeAddOp4(v, OP_VFilter, iCur, addrBrk, iReg, pVtabIdx->idxStr,
- pVtabIdx->needToFreeIdxStr ? P4_MPRINTF : P4_STATIC);
- pVtabIdx->needToFreeIdxStr = 0;
- for(j=0; j<nConstraint; j++){
- if( aUsage[j].omit ){
- int iTerm = aConstraint[j].iTermOffset;
- disableTerm(pLevel, &pWC->a[iTerm]);
- }
- }
- pLevel->op = OP_VNext;
- pLevel->p1 = iCur;
- pLevel->p2 = sqlite3VdbeCurrentAddr(v);
- sqlite3ReleaseTempRange(pParse, iReg, nConstraint+2);
- }else
-#endif /* SQLITE_OMIT_VIRTUALTABLE */
-
- if( pLevel->plan.wsFlags & WHERE_ROWID_EQ ){
- /* Case 1: We can directly reference a single row using an
- ** equality comparison against the ROWID field. Or
- ** we reference multiple rows using a "rowid IN (...)"
- ** construct.
- */
- iReleaseReg = sqlite3GetTempReg(pParse);
- pTerm = findTerm(pWC, iCur, -1, notReady, WO_EQ|WO_IN, 0);
- assert( pTerm!=0 );
- assert( pTerm->pExpr!=0 );
- assert( pTerm->leftCursor==iCur );
- assert( omitTable==0 );
- iRowidReg = codeEqualityTerm(pParse, pTerm, pLevel, iReleaseReg);
- addrNxt = pLevel->addrNxt;
- sqlite3VdbeAddOp2(v, OP_MustBeInt, iRowidReg, addrNxt);
- sqlite3VdbeAddOp3(v, OP_NotExists, iCur, addrNxt, iRowidReg);
- sqlite3ExprCacheStore(pParse, iCur, -1, iRowidReg);
- VdbeComment((v, "pk"));
- pLevel->op = OP_Noop;
- }else if( pLevel->plan.wsFlags & WHERE_ROWID_RANGE ){
- /* Case 2: We have an inequality comparison against the ROWID field.
- */
- int testOp = OP_Noop;
- int start;
- int memEndValue = 0;
- WhereTerm *pStart, *pEnd;
-
- assert( omitTable==0 );
- pStart = findTerm(pWC, iCur, -1, notReady, WO_GT|WO_GE, 0);
- pEnd = findTerm(pWC, iCur, -1, notReady, WO_LT|WO_LE, 0);
- if( bRev ){
- pTerm = pStart;
- pStart = pEnd;
- pEnd = pTerm;
- }
- if( pStart ){
- Expr *pX; /* The expression that defines the start bound */
- int r1, rTemp; /* Registers for holding the start boundary */
-
- /* The following constant maps TK_xx codes into corresponding
- ** seek opcodes. It depends on a particular ordering of TK_xx
- */
- const u8 aMoveOp[] = {
- /* TK_GT */ OP_SeekGt,
- /* TK_LE */ OP_SeekLe,
- /* TK_LT */ OP_SeekLt,
- /* TK_GE */ OP_SeekGe
- };
- assert( TK_LE==TK_GT+1 ); /* Make sure the ordering.. */
- assert( TK_LT==TK_GT+2 ); /* ... of the TK_xx values... */
- assert( TK_GE==TK_GT+3 ); /* ... is correcct. */
-
- pX = pStart->pExpr;
- assert( pX!=0 );
- assert( pStart->leftCursor==iCur );
- r1 = sqlite3ExprCodeTemp(pParse, pX->pRight, &rTemp);
- sqlite3VdbeAddOp3(v, aMoveOp[pX->op-TK_GT], iCur, addrBrk, r1);
- VdbeComment((v, "pk"));
- sqlite3ExprCacheAffinityChange(pParse, r1, 1);
- sqlite3ReleaseTempReg(pParse, rTemp);
- disableTerm(pLevel, pStart);
- }else{
- sqlite3VdbeAddOp2(v, bRev ? OP_Last : OP_Rewind, iCur, addrBrk);
- }
- if( pEnd ){
- Expr *pX;
- pX = pEnd->pExpr;
- assert( pX!=0 );
- assert( pEnd->leftCursor==iCur );
- memEndValue = ++pParse->nMem;
- sqlite3ExprCode(pParse, pX->pRight, memEndValue);
- if( pX->op==TK_LT || pX->op==TK_GT ){
- testOp = bRev ? OP_Le : OP_Ge;
- }else{
- testOp = bRev ? OP_Lt : OP_Gt;
- }
- disableTerm(pLevel, pEnd);
- }
- start = sqlite3VdbeCurrentAddr(v);
- pLevel->op = bRev ? OP_Prev : OP_Next;
- pLevel->p1 = iCur;
- pLevel->p2 = start;
- pLevel->p5 = (pStart==0 && pEnd==0) ?1:0;
- if( testOp!=OP_Noop ){
- iRowidReg = iReleaseReg = sqlite3GetTempReg(pParse);
- sqlite3VdbeAddOp2(v, OP_Rowid, iCur, iRowidReg);
- sqlite3ExprCacheStore(pParse, iCur, -1, iRowidReg);
- sqlite3VdbeAddOp3(v, testOp, memEndValue, addrBrk, iRowidReg);
- sqlite3VdbeChangeP5(v, SQLITE_AFF_NUMERIC | SQLITE_JUMPIFNULL);
- }
- }else if( pLevel->plan.wsFlags & (WHERE_COLUMN_RANGE|WHERE_COLUMN_EQ) ){
- /* Case 3: A scan using an index.
- **
- ** The WHERE clause may contain zero or more equality
- ** terms ("==" or "IN" operators) that refer to the N
- ** left-most columns of the index. It may also contain
- ** inequality constraints (>, <, >= or <=) on the indexed
- ** column that immediately follows the N equalities. Only
- ** the right-most column can be an inequality - the rest must
- ** use the "==" and "IN" operators. For example, if the
- ** index is on (x,y,z), then the following clauses are all
- ** optimized:
- **
- ** x=5
- ** x=5 AND y=10
- ** x=5 AND y<10
- ** x=5 AND y>5 AND y<10
- ** x=5 AND y=5 AND z<=10
- **
- ** The z<10 term of the following cannot be used, only
- ** the x=5 term:
- **
- ** x=5 AND z<10
- **
- ** N may be zero if there are inequality constraints.
- ** If there are no inequality constraints, then N is at
- ** least one.
- **
- ** This case is also used when there are no WHERE clause
- ** constraints but an index is selected anyway, in order
- ** to force the output order to conform to an ORDER BY.
- */
- int aStartOp[] = {
- 0,
- 0,
- OP_Rewind, /* 2: (!start_constraints && startEq && !bRev) */
- OP_Last, /* 3: (!start_constraints && startEq && bRev) */
- OP_SeekGt, /* 4: (start_constraints && !startEq && !bRev) */
- OP_SeekLt, /* 5: (start_constraints && !startEq && bRev) */
- OP_SeekGe, /* 6: (start_constraints && startEq && !bRev) */
- OP_SeekLe /* 7: (start_constraints && startEq && bRev) */
- };
- int aEndOp[] = {
- OP_Noop, /* 0: (!end_constraints) */
- OP_IdxGE, /* 1: (end_constraints && !bRev) */
- OP_IdxLT /* 2: (end_constraints && bRev) */
- };
- int nEq = pLevel->plan.nEq;
- int isMinQuery = 0; /* If this is an optimized SELECT min(x).. */
- int regBase; /* Base register holding constraint values */
- int r1; /* Temp register */
- WhereTerm *pRangeStart = 0; /* Inequality constraint at range start */
- WhereTerm *pRangeEnd = 0; /* Inequality constraint at range end */
- int startEq; /* True if range start uses ==, >= or <= */
- int endEq; /* True if range end uses ==, >= or <= */
- int start_constraints; /* Start of range is constrained */
- int nConstraint; /* Number of constraint terms */
- Index *pIdx; /* The index we will be using */
- int iIdxCur; /* The VDBE cursor for the index */
- int nExtraReg = 0; /* Number of extra registers needed */
- int op; /* Instruction opcode */
- char *zAff;
-
- pIdx = pLevel->plan.u.pIdx;
- iIdxCur = pLevel->iIdxCur;
- k = pIdx->aiColumn[nEq]; /* Column for inequality constraints */
-
- /* If this loop satisfies a sort order (pOrderBy) request that
- ** was passed to this function to implement a "SELECT min(x) ..."
- ** query, then the caller will only allow the loop to run for
- ** a single iteration. This means that the first row returned
- ** should not have a NULL value stored in 'x'. If column 'x' is
- ** the first one after the nEq equality constraints in the index,
- ** this requires some special handling.
- */
- if( (wctrlFlags&WHERE_ORDERBY_MIN)!=0
- && (pLevel->plan.wsFlags&WHERE_ORDERBY)
- && (pIdx->nColumn>nEq)
- ){
- /* assert( pOrderBy->nExpr==1 ); */
- /* assert( pOrderBy->a[0].pExpr->iColumn==pIdx->aiColumn[nEq] ); */
- isMinQuery = 1;
- nExtraReg = 1;
- }
-
- /* Find any inequality constraint terms for the start and end
- ** of the range.
- */
- if( pLevel->plan.wsFlags & WHERE_TOP_LIMIT ){
- pRangeEnd = findTerm(pWC, iCur, k, notReady, (WO_LT|WO_LE), pIdx);
- nExtraReg = 1;
- }
- if( pLevel->plan.wsFlags & WHERE_BTM_LIMIT ){
- pRangeStart = findTerm(pWC, iCur, k, notReady, (WO_GT|WO_GE), pIdx);
- nExtraReg = 1;
- }
-
- /* Generate code to evaluate all constraint terms using == or IN
- ** and store the values of those terms in an array of registers
- ** starting at regBase.
- */
- regBase = codeAllEqualityTerms(
- pParse, pLevel, pWC, notReady, nExtraReg, &zAff
- );
- addrNxt = pLevel->addrNxt;
-
- /* If we are doing a reverse order scan on an ascending index, or
- ** a forward order scan on a descending index, interchange the
- ** start and end terms (pRangeStart and pRangeEnd).
- */
- if( bRev==(pIdx->aSortOrder[nEq]==SQLITE_SO_ASC) ){
- SWAP(WhereTerm *, pRangeEnd, pRangeStart);
- }
-
- testcase( pRangeStart && pRangeStart->eOperator & WO_LE );
- testcase( pRangeStart && pRangeStart->eOperator & WO_GE );
- testcase( pRangeEnd && pRangeEnd->eOperator & WO_LE );
- testcase( pRangeEnd && pRangeEnd->eOperator & WO_GE );
- startEq = !pRangeStart || pRangeStart->eOperator & (WO_LE|WO_GE);
- endEq = !pRangeEnd || pRangeEnd->eOperator & (WO_LE|WO_GE);
- start_constraints = pRangeStart || nEq>0;
-
- /* Seek the index cursor to the start of the range. */
- nConstraint = nEq;
- if( pRangeStart ){
- Expr *pRight = pRangeStart->pExpr->pRight;
- sqlite3ExprCode(pParse, pRight, regBase+nEq);
- sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, addrNxt);
- if( zAff
- && sqlite3CompareAffinity(pRight, zAff[nConstraint])==SQLITE_AFF_NONE
- ){
- /* Since the comparison is to be performed with no conversions applied
- ** to the operands, set the affinity to apply to pRight to
- ** SQLITE_AFF_NONE. */
- zAff[nConstraint] = SQLITE_AFF_NONE;
- }
- nConstraint++;
- }else if( isMinQuery ){
- sqlite3VdbeAddOp2(v, OP_Null, 0, regBase+nEq);
- nConstraint++;
- startEq = 0;
- start_constraints = 1;
- }
- codeApplyAffinity(pParse, regBase, nConstraint, zAff);
- op = aStartOp[(start_constraints<<2) + (startEq<<1) + bRev];
- assert( op!=0 );
- testcase( op==OP_Rewind );
- testcase( op==OP_Last );
- testcase( op==OP_SeekGt );
- testcase( op==OP_SeekGe );
- testcase( op==OP_SeekLe );
- testcase( op==OP_SeekLt );
- sqlite3VdbeAddOp4(v, op, iIdxCur, addrNxt, regBase,
- SQLITE_INT_TO_PTR(nConstraint), P4_INT32);
-
- /* Load the value for the inequality constraint at the end of the
- ** range (if any).
- */
- nConstraint = nEq;
- if( pRangeEnd ){
- Expr *pRight = pRangeEnd->pExpr->pRight;
- sqlite3ExprCacheRemove(pParse, regBase+nEq);
- sqlite3ExprCode(pParse, pRight, regBase+nEq);
- sqlite3VdbeAddOp2(v, OP_IsNull, regBase+nEq, addrNxt);
- zAff = sqlite3DbStrDup(pParse->db, zAff);
- if( zAff
- && sqlite3CompareAffinity(pRight, zAff[nConstraint])==SQLITE_AFF_NONE
- ){
- /* Since the comparison is to be performed with no conversions applied
- ** to the operands, set the affinity to apply to pRight to
- ** SQLITE_AFF_NONE. */
- zAff[nConstraint] = SQLITE_AFF_NONE;
- }
- codeApplyAffinity(pParse, regBase, nEq+1, zAff);
- nConstraint++;
- }
-
- /* Top of the loop body */
- pLevel->p2 = sqlite3VdbeCurrentAddr(v);
-
- /* Check if the index cursor is past the end of the range. */
- op = aEndOp[(pRangeEnd || nEq) * (1 + bRev)];
- testcase( op==OP_Noop );
- testcase( op==OP_IdxGE );
- testcase( op==OP_IdxLT );
- if( op!=OP_Noop ){
- sqlite3VdbeAddOp4(v, op, iIdxCur, addrNxt, regBase,
- SQLITE_INT_TO_PTR(nConstraint), P4_INT32);
- sqlite3VdbeChangeP5(v, endEq!=bRev ?1:0);
- }
-
- /* If there are inequality constraints, check that the value
- ** of the table column that the inequality contrains is not NULL.
- ** If it is, jump to the next iteration of the loop.
- */
- r1 = sqlite3GetTempReg(pParse);
- testcase( pLevel->plan.wsFlags & WHERE_BTM_LIMIT );
- testcase( pLevel->plan.wsFlags & WHERE_TOP_LIMIT );
- if( pLevel->plan.wsFlags & (WHERE_BTM_LIMIT|WHERE_TOP_LIMIT) ){
- sqlite3VdbeAddOp3(v, OP_Column, iIdxCur, nEq, r1);
- sqlite3VdbeAddOp2(v, OP_IsNull, r1, addrCont);
- }
- sqlite3ReleaseTempReg(pParse, r1);
-
- /* Seek the table cursor, if required */
- disableTerm(pLevel, pRangeStart);
- disableTerm(pLevel, pRangeEnd);
- if( !omitTable ){
- iRowidReg = iReleaseReg = sqlite3GetTempReg(pParse);
- sqlite3VdbeAddOp2(v, OP_IdxRowid, iIdxCur, iRowidReg);
- sqlite3ExprCacheStore(pParse, iCur, -1, iRowidReg);
- sqlite3VdbeAddOp2(v, OP_Seek, iCur, iRowidReg); /* Deferred seek */
- }
-
- /* Record the instruction used to terminate the loop. Disable
- ** WHERE clause terms made redundant by the index range scan.
- */
- pLevel->op = bRev ? OP_Prev : OP_Next;
- pLevel->p1 = iIdxCur;
- }else
-
-#ifndef SQLITE_OMIT_OR_OPTIMIZATION
- if( pLevel->plan.wsFlags & WHERE_MULTI_OR ){
- /* Case 4: Two or more separately indexed terms connected by OR
- **
- ** Example:
- **
- ** CREATE TABLE t1(a,b,c,d);
- ** CREATE INDEX i1 ON t1(a);
- ** CREATE INDEX i2 ON t1(b);
- ** CREATE INDEX i3 ON t1(c);
- **
- ** SELECT * FROM t1 WHERE a=5 OR b=7 OR (c=11 AND d=13)
- **
- ** In the example, there are three indexed terms connected by OR.
- ** The top of the loop looks like this:
- **
- ** Null 1 # Zero the rowset in reg 1
- **
- ** Then, for each indexed term, the following. The arguments to
- ** RowSetTest are such that the rowid of the current row is inserted
- ** into the RowSet. If it is already present, control skips the
- ** Gosub opcode and jumps straight to the code generated by WhereEnd().
- **
- ** sqlite3WhereBegin(<term>)
- ** RowSetTest # Insert rowid into rowset
- ** Gosub 2 A
- ** sqlite3WhereEnd()
- **
- ** Following the above, code to terminate the loop. Label A, the target
- ** of the Gosub above, jumps to the instruction right after the Goto.
- **
- ** Null 1 # Zero the rowset in reg 1
- ** Goto B # The loop is finished.
- **
- ** A: <loop body> # Return data, whatever.
- **
- ** Return 2 # Jump back to the Gosub
- **
- ** B: <after the loop>
- **
- */
- WhereClause *pOrWc; /* The OR-clause broken out into subterms */
- WhereTerm *pFinal; /* Final subterm within the OR-clause. */
- SrcList oneTab; /* Shortened table list */
-
- int regReturn = ++pParse->nMem; /* Register used with OP_Gosub */
- int regRowset = 0; /* Register for RowSet object */
- int regRowid = 0; /* Register holding rowid */
- int iLoopBody = sqlite3VdbeMakeLabel(v); /* Start of loop body */
- int iRetInit; /* Address of regReturn init */
- int ii;
-
- pTerm = pLevel->plan.u.pTerm;
- assert( pTerm!=0 );
- assert( pTerm->eOperator==WO_OR );
- assert( (pTerm->wtFlags & TERM_ORINFO)!=0 );
- pOrWc = &pTerm->u.pOrInfo->wc;
- pFinal = &pOrWc->a[pOrWc->nTerm-1];
-
- /* Set up a SrcList containing just the table being scanned by this loop. */
- oneTab.nSrc = 1;
- oneTab.nAlloc = 1;
- oneTab.a[0] = *pTabItem;
-
- /* Initialize the rowset register to contain NULL. An SQL NULL is
- ** equivalent to an empty rowset.
- **
- ** Also initialize regReturn to contain the address of the instruction
- ** immediately following the OP_Return at the bottom of the loop. This
- ** is required in a few obscure LEFT JOIN cases where control jumps
- ** over the top of the loop into the body of it. In this case the
- ** correct response for the end-of-loop code (the OP_Return) is to
- ** fall through to the next instruction, just as an OP_Next does if
- ** called on an uninitialized cursor.
- */
- if( (wctrlFlags & WHERE_DUPLICATES_OK)==0 ){
- regRowset = ++pParse->nMem;
- regRowid = ++pParse->nMem;
- sqlite3VdbeAddOp2(v, OP_Null, 0, regRowset);
- }
- iRetInit = sqlite3VdbeAddOp2(v, OP_Integer, 0, regReturn);
-
- for(ii=0; ii<pOrWc->nTerm; ii++){
- WhereTerm *pOrTerm = &pOrWc->a[ii];
- if( pOrTerm->leftCursor==iCur || pOrTerm->eOperator==WO_AND ){
- WhereInfo *pSubWInfo; /* Info for single OR-term scan */
- /* Loop through table entries that match term pOrTerm. */
- pSubWInfo = sqlite3WhereBegin(pParse, &oneTab, pOrTerm->pExpr, 0,
- WHERE_OMIT_OPEN | WHERE_OMIT_CLOSE | WHERE_FORCE_TABLE);
- if( pSubWInfo ){
- if( (wctrlFlags & WHERE_DUPLICATES_OK)==0 ){
- int iSet = ((ii==pOrWc->nTerm-1)?-1:ii);
- int r;
- r = sqlite3ExprCodeGetColumn(pParse, pTabItem->pTab, -1, iCur,
- regRowid, 0);
- sqlite3VdbeAddOp4(v, OP_RowSetTest, regRowset,
- sqlite3VdbeCurrentAddr(v)+2,
- r, SQLITE_INT_TO_PTR(iSet), P4_INT32);
- }
- sqlite3VdbeAddOp2(v, OP_Gosub, regReturn, iLoopBody);
-
- /* Finish the loop through table entries that match term pOrTerm. */
- sqlite3WhereEnd(pSubWInfo);
- }
- }
- }
- sqlite3VdbeChangeP1(v, iRetInit, sqlite3VdbeCurrentAddr(v));
- /* sqlite3VdbeAddOp2(v, OP_Null, 0, regRowset); */
- sqlite3VdbeAddOp2(v, OP_Goto, 0, pLevel->addrBrk);
- sqlite3VdbeResolveLabel(v, iLoopBody);
-
- pLevel->op = OP_Return;
- pLevel->p1 = regReturn;
- disableTerm(pLevel, pTerm);
- }else
-#endif /* SQLITE_OMIT_OR_OPTIMIZATION */
-
- {
- /* Case 5: There is no usable index. We must do a complete
- ** scan of the entire table.
- */
- static const u8 aStep[] = { OP_Next, OP_Prev };
- static const u8 aStart[] = { OP_Rewind, OP_Last };
- assert( bRev==0 || bRev==1 );
- assert( omitTable==0 );
- pLevel->op = aStep[bRev];
- pLevel->p1 = iCur;
- pLevel->p2 = 1 + sqlite3VdbeAddOp2(v, aStart[bRev], iCur, addrBrk);
- pLevel->p5 = SQLITE_STMTSTATUS_FULLSCAN_STEP;
- }
- notReady &= ~getMask(pWC->pMaskSet, iCur);
-
- /* Insert code to test every subexpression that can be completely
- ** computed using the current set of tables.
- */
- k = 0;
- for(pTerm=pWC->a, j=pWC->nTerm; j>0; j--, pTerm++){
- Expr *pE;
- testcase( pTerm->wtFlags & TERM_VIRTUAL );
- testcase( pTerm->wtFlags & TERM_CODED );
- if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
- if( (pTerm->prereqAll & notReady)!=0 ) continue;
- pE = pTerm->pExpr;
- assert( pE!=0 );
- if( pLevel->iLeftJoin && !ExprHasProperty(pE, EP_FromJoin) ){
- continue;
- }
- sqlite3ExprIfFalse(pParse, pE, addrCont, SQLITE_JUMPIFNULL);
- k = 1;
- pTerm->wtFlags |= TERM_CODED;
- }
-
- /* For a LEFT OUTER JOIN, generate code that will record the fact that
- ** at least one row of the right table has matched the left table.
- */
- if( pLevel->iLeftJoin ){
- pLevel->addrFirst = sqlite3VdbeCurrentAddr(v);
- sqlite3VdbeAddOp2(v, OP_Integer, 1, pLevel->iLeftJoin);
- VdbeComment((v, "record LEFT JOIN hit"));
- sqlite3ExprCacheClear(pParse);
- for(pTerm=pWC->a, j=0; j<pWC->nTerm; j++, pTerm++){
- testcase( pTerm->wtFlags & TERM_VIRTUAL );
- testcase( pTerm->wtFlags & TERM_CODED );
- if( pTerm->wtFlags & (TERM_VIRTUAL|TERM_CODED) ) continue;
- if( (pTerm->prereqAll & notReady)!=0 ) continue;
- assert( pTerm->pExpr );
- sqlite3ExprIfFalse(pParse, pTerm->pExpr, addrCont, SQLITE_JUMPIFNULL);
- pTerm->wtFlags |= TERM_CODED;
- }
- }
- sqlite3ReleaseTempReg(pParse, iReleaseReg);
-
- return notReady;
-}
-
-#if defined(SQLITE_TEST)
-/*
-** The following variable holds a text description of query plan generated
-** by the most recent call to sqlite3WhereBegin(). Each call to WhereBegin
-** overwrites the previous. This information is used for testing and
-** analysis only.
-*/
-char sqlite3_query_plan[BMS*2*40]; /* Text of the join */
-static int nQPlan = 0; /* Next free slow in _query_plan[] */
-
-#endif /* SQLITE_TEST */
-
-
-/*
-** Free a WhereInfo structure
-*/
-static void whereInfoFree(sqlite3 *db, WhereInfo *pWInfo){
- if( pWInfo ){
- int i;
- for(i=0; i<pWInfo->nLevel; i++){
- sqlite3_index_info *pInfo = pWInfo->a[i].pIdxInfo;
- if( pInfo ){
- /* assert( pInfo->needToFreeIdxStr==0 || db->mallocFailed ); */
- if( pInfo->needToFreeIdxStr ){
- sqlite3_free(pInfo->idxStr);
- }
- sqlite3DbFree(db, pInfo);
- }
- }
- whereClauseClear(pWInfo->pWC);
- sqlite3DbFree(db, pWInfo);
- }
-}
-
-
-/*
-** Generate the beginning of the loop used for WHERE clause processing.
-** The return value is a pointer to an opaque structure that contains
-** information needed to terminate the loop. Later, the calling routine
-** should invoke sqlite3WhereEnd() with the return value of this function
-** in order to complete the WHERE clause processing.
-**
-** If an error occurs, this routine returns NULL.
-**
-** The basic idea is to do a nested loop, one loop for each table in
-** the FROM clause of a select. (INSERT and UPDATE statements are the
-** same as a SELECT with only a single table in the FROM clause.) For
-** example, if the SQL is this:
-**
-** SELECT * FROM t1, t2, t3 WHERE ...;
-**
-** Then the code generated is conceptually like the following:
-**
-** foreach row1 in t1 do \ Code generated
-** foreach row2 in t2 do |-- by sqlite3WhereBegin()
-** foreach row3 in t3 do /
-** ...
-** end \ Code generated
-** end |-- by sqlite3WhereEnd()
-** end /
-**
-** Note that the loops might not be nested in the order in which they
-** appear in the FROM clause if a different order is better able to make
-** use of indices. Note also that when the IN operator appears in
-** the WHERE clause, it might result in additional nested loops for
-** scanning through all values on the right-hand side of the IN.
-**
-** There are Btree cursors associated with each table. t1 uses cursor
-** number pTabList->a[0].iCursor. t2 uses the cursor pTabList->a[1].iCursor.
-** And so forth. This routine generates code to open those VDBE cursors
-** and sqlite3WhereEnd() generates the code to close them.
-**
-** The code that sqlite3WhereBegin() generates leaves the cursors named
-** in pTabList pointing at their appropriate entries. The [...] code
-** can use OP_Column and OP_Rowid opcodes on these cursors to extract
-** data from the various tables of the loop.
-**
-** If the WHERE clause is empty, the foreach loops must each scan their
-** entire tables. Thus a three-way join is an O(N^3) operation. But if
-** the tables have indices and there are terms in the WHERE clause that
-** refer to those indices, a complete table scan can be avoided and the
-** code will run much faster. Most of the work of this routine is checking
-** to see if there are indices that can be used to speed up the loop.
-**
-** Terms of the WHERE clause are also used to limit which rows actually
-** make it to the "..." in the middle of the loop. After each "foreach",
-** terms of the WHERE clause that use only terms in that loop and outer
-** loops are evaluated and if false a jump is made around all subsequent
-** inner loops (or around the "..." if the test occurs within the inner-
-** most loop)
-**
-** OUTER JOINS
-**
-** An outer join of tables t1 and t2 is conceptally coded as follows:
-**
-** foreach row1 in t1 do
-** flag = 0
-** foreach row2 in t2 do
-** start:
-** ...
-** flag = 1
-** end
-** if flag==0 then
-** move the row2 cursor to a null row
-** goto start
-** fi
-** end
-**
-** ORDER BY CLAUSE PROCESSING
-**
-** *ppOrderBy is a pointer to the ORDER BY clause of a SELECT statement,
-** if there is one. If there is no ORDER BY clause or if this routine
-** is called from an UPDATE or DELETE statement, then ppOrderBy is NULL.
-**
-** If an index can be used so that the natural output order of the table
-** scan is correct for the ORDER BY clause, then that index is used and
-** *ppOrderBy is set to NULL. This is an optimization that prevents an
-** unnecessary sort of the result set if an index appropriate for the
-** ORDER BY clause already exists.
-**
-** If the where clause loops cannot be arranged to provide the correct
-** output order, then the *ppOrderBy is unchanged.
-*/
-WhereInfo *sqlite3WhereBegin(
- Parse *pParse, /* The parser context */
- SrcList *pTabList, /* A list of all tables to be scanned */
- Expr *pWhere, /* The WHERE clause */
- ExprList **ppOrderBy, /* An ORDER BY clause, or NULL */
- u16 wctrlFlags /* One of the WHERE_* flags defined in sqliteInt.h */
-){
- int i; /* Loop counter */
- int nByteWInfo; /* Num. bytes allocated for WhereInfo struct */
- WhereInfo *pWInfo; /* Will become the return value of this function */
- Vdbe *v = pParse->pVdbe; /* The virtual database engine */
- Bitmask notReady; /* Cursors that are not yet positioned */
- WhereMaskSet *pMaskSet; /* The expression mask set */
- WhereClause *pWC; /* Decomposition of the WHERE clause */
- struct SrcList_item *pTabItem; /* A single entry from pTabList */
- WhereLevel *pLevel; /* A single level in the pWInfo list */
- int iFrom; /* First unused FROM clause element */
- int andFlags; /* AND-ed combination of all pWC->a[].wtFlags */
- sqlite3 *db; /* Database connection */
-
- /* The number of tables in the FROM clause is limited by the number of
- ** bits in a Bitmask
- */
- if( pTabList->nSrc>BMS ){
- sqlite3ErrorMsg(pParse, "at most %d tables in a join", BMS);
- return 0;
- }
-
- /* Allocate and initialize the WhereInfo structure that will become the
- ** return value. A single allocation is used to store the WhereInfo
- ** struct, the contents of WhereInfo.a[], the WhereClause structure
- ** and the WhereMaskSet structure. Since WhereClause contains an 8-byte
- ** field (type Bitmask) it must be aligned on an 8-byte boundary on
- ** some architectures. Hence the ROUND8() below.
- */
- db = pParse->db;
- nByteWInfo = ROUND8(sizeof(WhereInfo)+(pTabList->nSrc-1)*sizeof(WhereLevel));
- pWInfo = sqlite3DbMallocZero(db,
- nByteWInfo +
- sizeof(WhereClause) +
- sizeof(WhereMaskSet)
- );
- if( db->mallocFailed ){
- goto whereBeginError;
- }
- pWInfo->nLevel = pTabList->nSrc;
- pWInfo->pParse = pParse;
- pWInfo->pTabList = pTabList;
- pWInfo->iBreak = sqlite3VdbeMakeLabel(v);
- pWInfo->pWC = pWC = (WhereClause *)&((u8 *)pWInfo)[nByteWInfo];
- pWInfo->wctrlFlags = wctrlFlags;
- pMaskSet = (WhereMaskSet*)&pWC[1];
-
- /* Split the WHERE clause into separate subexpressions where each
- ** subexpression is separated by an AND operator.
- */
- initMaskSet(pMaskSet);
- whereClauseInit(pWC, pParse, pMaskSet);
- sqlite3ExprCodeConstants(pParse, pWhere);
- whereSplit(pWC, pWhere, TK_AND);
-
- /* Special case: a WHERE clause that is constant. Evaluate the
- ** expression and either jump over all of the code or fall thru.
- */
- if( pWhere && (pTabList->nSrc==0 || sqlite3ExprIsConstantNotJoin(pWhere)) ){
- sqlite3ExprIfFalse(pParse, pWhere, pWInfo->iBreak, SQLITE_JUMPIFNULL);
- pWhere = 0;
- }
-
- /* Assign a bit from the bitmask to every term in the FROM clause.
- **
- ** When assigning bitmask values to FROM clause cursors, it must be
- ** the case that if X is the bitmask for the N-th FROM clause term then
- ** the bitmask for all FROM clause terms to the left of the N-th term
- ** is (X-1). An expression from the ON clause of a LEFT JOIN can use
- ** its Expr.iRightJoinTable value to find the bitmask of the right table
- ** of the join. Subtracting one from the right table bitmask gives a
- ** bitmask for all tables to the left of the join. Knowing the bitmask
- ** for all tables to the left of a left join is important. Ticket #3015.
- **
- ** Configure the WhereClause.vmask variable so that bits that correspond
- ** to virtual table cursors are set. This is used to selectively disable
- ** the OR-to-IN transformation in exprAnalyzeOrTerm(). It is not helpful
- ** with virtual tables.
- */
- assert( pWC->vmask==0 && pMaskSet->n==0 );
- for(i=0; i<pTabList->nSrc; i++){
- createMask(pMaskSet, pTabList->a[i].iCursor);
-#ifndef SQLITE_OMIT_VIRTUALTABLE
- if( ALWAYS(pTabList->a[i].pTab) && IsVirtual(pTabList->a[i].pTab) ){
- pWC->vmask |= ((Bitmask)1 << i);
- }
-#endif
- }
-#ifndef NDEBUG
- {
- Bitmask toTheLeft = 0;
- for(i=0; i<pTabList->nSrc; i++){
- Bitmask m = getMask(pMaskSet, pTabList->a[i].iCursor);
- assert( (m-1)==toTheLeft );
- toTheLeft |= m;
- }
- }
-#endif
-
- /* Analyze all of the subexpressions. Note that exprAnalyze() might
- ** add new virtual terms onto the end of the WHERE clause. We do not
- ** want to analyze these virtual terms, so start analyzing at the end
- ** and work forward so that the added virtual terms are never processed.
- */
- exprAnalyzeAll(pTabList, pWC);
- if( db->mallocFailed ){
- goto whereBeginError;
- }
-
- /* Chose the best index to use for each table in the FROM clause.
- **
- ** This loop fills in the following fields:
- **
- ** pWInfo->a[].pIdx The index to use for this level of the loop.
- ** pWInfo->a[].wsFlags WHERE_xxx flags associated with pIdx
- ** pWInfo->a[].nEq The number of == and IN constraints
- ** pWInfo->a[].iFrom Which term of the FROM clause is being coded
- ** pWInfo->a[].iTabCur The VDBE cursor for the database table
- ** pWInfo->a[].iIdxCur The VDBE cursor for the index
- ** pWInfo->a[].pTerm When wsFlags==WO_OR, the OR-clause term
- **
- ** This loop also figures out the nesting order of tables in the FROM
- ** clause.
- */
- notReady = ~(Bitmask)0;
- pTabItem = pTabList->a;
- pLevel = pWInfo->a;
- andFlags = ~0;
- WHERETRACE(("*** Optimizer Start ***\n"));
- for(i=iFrom=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){
- WhereCost bestPlan; /* Most efficient plan seen so far */
- Index *pIdx; /* Index for FROM table at pTabItem */
- int j; /* For looping over FROM tables */
- int bestJ = -1; /* The value of j */
- Bitmask m; /* Bitmask value for j or bestJ */
- int isOptimal; /* Iterator for optimal/non-optimal search */
-
- memset(&bestPlan, 0, sizeof(bestPlan));
- bestPlan.rCost = SQLITE_BIG_DBL;
-
- /* Loop through the remaining entries in the FROM clause to find the
- ** next nested loop. The FROM clause entries may be iterated through
- ** either once or twice.
- **
- ** The first iteration, which is always performed, searches for the
- ** FROM clause entry that permits the lowest-cost, "optimal" scan. In
- ** this context an optimal scan is one that uses the same strategy
- ** for the given FROM clause entry as would be selected if the entry
- ** were used as the innermost nested loop. In other words, a table
- ** is chosen such that the cost of running that table cannot be reduced
- ** by waiting for other tables to run first.
- **
- ** The second iteration is only performed if no optimal scan strategies
- ** were found by the first. This iteration is used to search for the
- ** lowest cost scan overall.
- **
- ** Previous versions of SQLite performed only the second iteration -
- ** the next outermost loop was always that with the lowest overall
- ** cost. However, this meant that SQLite could select the wrong plan
- ** for scripts such as the following:
- **
- ** CREATE TABLE t1(a, b);
- ** CREATE TABLE t2(c, d);
- ** SELECT * FROM t2, t1 WHERE t2.rowid = t1.a;
- **
- ** The best strategy is to iterate through table t1 first. However it
- ** is not possible to determine this with a simple greedy algorithm.
- ** However, since the cost of a linear scan through table t2 is the same
- ** as the cost of a linear scan through table t1, a simple greedy
- ** algorithm may choose to use t2 for the outer loop, which is a much
- ** costlier approach.
- */
- for(isOptimal=1; isOptimal>=0 && bestJ<0; isOptimal--){
- Bitmask mask = (isOptimal ? 0 : notReady);
- assert( (pTabList->nSrc-iFrom)>1 || isOptimal );
- for(j=iFrom, pTabItem=&pTabList->a[j]; j<pTabList->nSrc; j++, pTabItem++){
- int doNotReorder; /* True if this table should not be reordered */
- WhereCost sCost; /* Cost information from best[Virtual]Index() */
- ExprList *pOrderBy; /* ORDER BY clause for index to optimize */
-
- doNotReorder = (pTabItem->jointype & (JT_LEFT|JT_CROSS))!=0;
- if( j!=iFrom && doNotReorder ) break;
- m = getMask(pMaskSet, pTabItem->iCursor);
- if( (m & notReady)==0 ){
- if( j==iFrom ) iFrom++;
- continue;
- }
- pOrderBy = ((i==0 && ppOrderBy )?*ppOrderBy:0);
-
- assert( pTabItem->pTab );
-#ifndef SQLITE_OMIT_VIRTUALTABLE
- if( IsVirtual(pTabItem->pTab) ){
- sqlite3_index_info **pp = &pWInfo->a[j].pIdxInfo;
- bestVirtualIndex(pParse, pWC, pTabItem, mask, pOrderBy, &sCost, pp);
- }else
-#endif
- {
- bestBtreeIndex(pParse, pWC, pTabItem, mask, pOrderBy, &sCost);
- }
- assert( isOptimal || (sCost.used&notReady)==0 );
-
- if( (sCost.used&notReady)==0
- && (j==iFrom || sCost.rCost<bestPlan.rCost)
- ){
- bestPlan = sCost;
- bestJ = j;
- }
- if( doNotReorder ) break;
- }
- }
- assert( bestJ>=0 );
- assert( notReady & getMask(pMaskSet, pTabList->a[bestJ].iCursor) );
- WHERETRACE(("*** Optimizer selects table %d for loop %d\n", bestJ,
- pLevel-pWInfo->a));
- if( (bestPlan.plan.wsFlags & WHERE_ORDERBY)!=0 ){
- *ppOrderBy = 0;
- }
- andFlags &= bestPlan.plan.wsFlags;
- pLevel->plan = bestPlan.plan;
- if( bestPlan.plan.wsFlags & WHERE_INDEXED ){
- pLevel->iIdxCur = pParse->nTab++;
- }else{
- pLevel->iIdxCur = -1;
- }
- notReady &= ~getMask(pMaskSet, pTabList->a[bestJ].iCursor);
- pLevel->iFrom = (u8)bestJ;
-
- /* Check that if the table scanned by this loop iteration had an
- ** INDEXED BY clause attached to it, that the named index is being
- ** used for the scan. If not, then query compilation has failed.
- ** Return an error.
- */
- pIdx = pTabList->a[bestJ].pIndex;
- if( pIdx ){
- if( (bestPlan.plan.wsFlags & WHERE_INDEXED)==0 ){
- sqlite3ErrorMsg(pParse, "cannot use index: %s", pIdx->zName);
- goto whereBeginError;
- }else{
- /* If an INDEXED BY clause is used, the bestIndex() function is
- ** guaranteed to find the index specified in the INDEXED BY clause
- ** if it find an index at all. */
- assert( bestPlan.plan.u.pIdx==pIdx );
- }
- }
- }
- WHERETRACE(("*** Optimizer Finished ***\n"));
- if( pParse->nErr || db->mallocFailed ){
- goto whereBeginError;
- }
-
- /* If the total query only selects a single row, then the ORDER BY
- ** clause is irrelevant.
- */
- if( (andFlags & WHERE_UNIQUE)!=0 && ppOrderBy ){
- *ppOrderBy = 0;
- }
-
- /* If the caller is an UPDATE or DELETE statement that is requesting
- ** to use a one-pass algorithm, determine if this is appropriate.
- ** The one-pass algorithm only works if the WHERE clause constraints
- ** the statement to update a single row.
- */
- assert( (wctrlFlags & WHERE_ONEPASS_DESIRED)==0 || pWInfo->nLevel==1 );
- if( (wctrlFlags & WHERE_ONEPASS_DESIRED)!=0 && (andFlags & WHERE_UNIQUE)!=0 ){
- pWInfo->okOnePass = 1;
- pWInfo->a[0].plan.wsFlags &= ~WHERE_IDX_ONLY;
- }
-
- /* Open all tables in the pTabList and any indices selected for
- ** searching those tables.
- */
- sqlite3CodeVerifySchema(pParse, -1); /* Insert the cookie verifier Goto */
- for(i=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){
- Table *pTab; /* Table to open */
- int iDb; /* Index of database containing table/index */
-
-#ifndef SQLITE_OMIT_EXPLAIN
- if( pParse->explain==2 ){
- char *zMsg;
- struct SrcList_item *pItem = &pTabList->a[pLevel->iFrom];
- zMsg = sqlite3MPrintf(db, "TABLE %s", pItem->zName);
- if( pItem->zAlias ){
- zMsg = sqlite3MAppendf(db, zMsg, "%s AS %s", zMsg, pItem->zAlias);
- }
- if( (pLevel->plan.wsFlags & WHERE_INDEXED)!=0 ){
- zMsg = sqlite3MAppendf(db, zMsg, "%s WITH INDEX %s",
- zMsg, pLevel->plan.u.pIdx->zName);
- }else if( pLevel->plan.wsFlags & WHERE_MULTI_OR ){
- zMsg = sqlite3MAppendf(db, zMsg, "%s VIA MULTI-INDEX UNION", zMsg);
- }else if( pLevel->plan.wsFlags & (WHERE_ROWID_EQ|WHERE_ROWID_RANGE) ){
- zMsg = sqlite3MAppendf(db, zMsg, "%s USING PRIMARY KEY", zMsg);
- }
-#ifndef SQLITE_OMIT_VIRTUALTABLE
- else if( (pLevel->plan.wsFlags & WHERE_VIRTUALTABLE)!=0 ){
- sqlite3_index_info *pVtabIdx = pLevel->plan.u.pVtabIdx;
- zMsg = sqlite3MAppendf(db, zMsg, "%s VIRTUAL TABLE INDEX %d:%s", zMsg,
- pVtabIdx->idxNum, pVtabIdx->idxStr);
- }
-#endif
- if( pLevel->plan.wsFlags & WHERE_ORDERBY ){
- zMsg = sqlite3MAppendf(db, zMsg, "%s ORDER BY", zMsg);
- }
- sqlite3VdbeAddOp4(v, OP_Explain, i, pLevel->iFrom, 0, zMsg, P4_DYNAMIC);
- }
-#endif /* SQLITE_OMIT_EXPLAIN */
- pTabItem = &pTabList->a[pLevel->iFrom];
- pTab = pTabItem->pTab;
- iDb = sqlite3SchemaToIndex(db, pTab->pSchema);
- if( (pTab->tabFlags & TF_Ephemeral)!=0 || pTab->pSelect ) continue;
-#ifndef SQLITE_OMIT_VIRTUALTABLE
- if( (pLevel->plan.wsFlags & WHERE_VIRTUALTABLE)!=0 ){
- const char *pVTab = (const char *)sqlite3GetVTable(db, pTab);
- int iCur = pTabItem->iCursor;
- sqlite3VdbeAddOp4(v, OP_VOpen, iCur, 0, 0, pVTab, P4_VTAB);
- }else
-#endif
- if( (pLevel->plan.wsFlags & WHERE_IDX_ONLY)==0
- && (wctrlFlags & WHERE_OMIT_OPEN)==0 ){
- int op = pWInfo->okOnePass ? OP_OpenWrite : OP_OpenRead;
- sqlite3OpenTable(pParse, pTabItem->iCursor, iDb, pTab, op);
- if( !pWInfo->okOnePass && pTab->nCol<BMS ){
- Bitmask b = pTabItem->colUsed;
- int n = 0;
- for(; b; b=b>>1, n++){}
- sqlite3VdbeChangeP4(v, sqlite3VdbeCurrentAddr(v)-1, SQLITE_INT_TO_PTR(n), P4_INT32);
- assert( n<=pTab->nCol );
- }
- }else{
- sqlite3TableLock(pParse, iDb, pTab->tnum, 0, pTab->zName);
- }
- pLevel->iTabCur = pTabItem->iCursor;
- if( (pLevel->plan.wsFlags & WHERE_INDEXED)!=0 ){
- Index *pIx = pLevel->plan.u.pIdx;
- KeyInfo *pKey = sqlite3IndexKeyinfo(pParse, pIx);
- int iIdxCur = pLevel->iIdxCur;
- assert( pIx->pSchema==pTab->pSchema );
- assert( iIdxCur>=0 );
- sqlite3VdbeAddOp4(v, OP_OpenRead, iIdxCur, pIx->tnum, iDb,
- (char*)pKey, P4_KEYINFO_HANDOFF);
- VdbeComment((v, "%s", pIx->zName));
- }
- sqlite3CodeVerifySchema(pParse, iDb);
- }
- pWInfo->iTop = sqlite3VdbeCurrentAddr(v);
-
- /* Generate the code to do the search. Each iteration of the for
- ** loop below generates code for a single nested loop of the VM
- ** program.
- */
- notReady = ~(Bitmask)0;
- for(i=0; i<pTabList->nSrc; i++){
- notReady = codeOneLoopStart(pWInfo, i, wctrlFlags, notReady);
- pWInfo->iContinue = pWInfo->a[i].addrCont;
- }
-
-#ifdef SQLITE_TEST /* For testing and debugging use only */
- /* Record in the query plan information about the current table
- ** and the index used to access it (if any). If the table itself
- ** is not used, its name is just '{}'. If no index is used
- ** the index is listed as "{}". If the primary key is used the
- ** index name is '*'.
- */
- for(i=0; i<pTabList->nSrc; i++){
- char *z;
- int n;
- pLevel = &pWInfo->a[i];
- pTabItem = &pTabList->a[pLevel->iFrom];
- z = pTabItem->zAlias;
- if( z==0 ) z = pTabItem->pTab->zName;
- n = sqlite3Strlen30(z);
- if( n+nQPlan < sizeof(sqlite3_query_plan)-10 ){
- if( pLevel->plan.wsFlags & WHERE_IDX_ONLY ){
- memcpy(&sqlite3_query_plan[nQPlan], "{}", 2);
- nQPlan += 2;
- }else{
- memcpy(&sqlite3_query_plan[nQPlan], z, n);
- nQPlan += n;
- }
- sqlite3_query_plan[nQPlan++] = ' ';
- }
- testcase( pLevel->plan.wsFlags & WHERE_ROWID_EQ );
- testcase( pLevel->plan.wsFlags & WHERE_ROWID_RANGE );
- if( pLevel->plan.wsFlags & (WHERE_ROWID_EQ|WHERE_ROWID_RANGE) ){
- memcpy(&sqlite3_query_plan[nQPlan], "* ", 2);
- nQPlan += 2;
- }else if( (pLevel->plan.wsFlags & WHERE_INDEXED)!=0 ){
- n = sqlite3Strlen30(pLevel->plan.u.pIdx->zName);
- if( n+nQPlan < sizeof(sqlite3_query_plan)-2 ){
- memcpy(&sqlite3_query_plan[nQPlan], pLevel->plan.u.pIdx->zName, n);
- nQPlan += n;
- sqlite3_query_plan[nQPlan++] = ' ';
- }
- }else{
- memcpy(&sqlite3_query_plan[nQPlan], "{} ", 3);
- nQPlan += 3;
- }
- }
- while( nQPlan>0 && sqlite3_query_plan[nQPlan-1]==' ' ){
- sqlite3_query_plan[--nQPlan] = 0;
- }
- sqlite3_query_plan[nQPlan] = 0;
- nQPlan = 0;
-#endif /* SQLITE_TEST // Testing and debugging use only */
-
- /* Record the continuation address in the WhereInfo structure. Then
- ** clean up and return.
- */
- return pWInfo;
-
- /* Jump here if malloc fails */
-whereBeginError:
- whereInfoFree(db, pWInfo);
- return 0;
-}
-
-/*
-** Generate the end of the WHERE loop. See comments on
-** sqlite3WhereBegin() for additional information.
-*/
-void sqlite3WhereEnd(WhereInfo *pWInfo){
- Parse *pParse = pWInfo->pParse;
- Vdbe *v = pParse->pVdbe;
- int i;
- WhereLevel *pLevel;
- SrcList *pTabList = pWInfo->pTabList;
- sqlite3 *db = pParse->db;
-
- /* Generate loop termination code.
- */
- sqlite3ExprCacheClear(pParse);
- for(i=pTabList->nSrc-1; i>=0; i--){
- pLevel = &pWInfo->a[i];
- sqlite3VdbeResolveLabel(v, pLevel->addrCont);
- if( pLevel->op!=OP_Noop ){
- sqlite3VdbeAddOp2(v, pLevel->op, pLevel->p1, pLevel->p2);
- sqlite3VdbeChangeP5(v, pLevel->p5);
- }
- if( pLevel->plan.wsFlags & WHERE_IN_ABLE && pLevel->u.in.nIn>0 ){
- struct InLoop *pIn;
- int j;
- sqlite3VdbeResolveLabel(v, pLevel->addrNxt);
- for(j=pLevel->u.in.nIn, pIn=&pLevel->u.in.aInLoop[j-1]; j>0; j--, pIn--){
- sqlite3VdbeJumpHere(v, pIn->addrInTop+1);
- sqlite3VdbeAddOp2(v, OP_Next, pIn->iCur, pIn->addrInTop);
- sqlite3VdbeJumpHere(v, pIn->addrInTop-1);
- }
- sqlite3DbFree(db, pLevel->u.in.aInLoop);
- }
- sqlite3VdbeResolveLabel(v, pLevel->addrBrk);
- if( pLevel->iLeftJoin ){
- int addr;
- addr = sqlite3VdbeAddOp1(v, OP_IfPos, pLevel->iLeftJoin);
- sqlite3VdbeAddOp1(v, OP_NullRow, pTabList->a[i].iCursor);
- if( pLevel->iIdxCur>=0 ){
- sqlite3VdbeAddOp1(v, OP_NullRow, pLevel->iIdxCur);
- }
- if( pLevel->op==OP_Return ){
- sqlite3VdbeAddOp2(v, OP_Gosub, pLevel->p1, pLevel->addrFirst);
- }else{
- sqlite3VdbeAddOp2(v, OP_Goto, 0, pLevel->addrFirst);
- }
- sqlite3VdbeJumpHere(v, addr);
- }
- }
-
- /* The "break" point is here, just past the end of the outer loop.
- ** Set it.
- */
- sqlite3VdbeResolveLabel(v, pWInfo->iBreak);
-
- /* Close all of the cursors that were opened by sqlite3WhereBegin.
- */
- for(i=0, pLevel=pWInfo->a; i<pTabList->nSrc; i++, pLevel++){
- struct SrcList_item *pTabItem = &pTabList->a[pLevel->iFrom];
- Table *pTab = pTabItem->pTab;
- assert( pTab!=0 );
- if( (pTab->tabFlags & TF_Ephemeral)!=0 || pTab->pSelect ) continue;
- if( (pWInfo->wctrlFlags & WHERE_OMIT_CLOSE)==0 ){
- if( !pWInfo->okOnePass && (pLevel->plan.wsFlags & WHERE_IDX_ONLY)==0 ){
- sqlite3VdbeAddOp1(v, OP_Close, pTabItem->iCursor);
- }
- if( (pLevel->plan.wsFlags & WHERE_INDEXED)!=0 ){
- sqlite3VdbeAddOp1(v, OP_Close, pLevel->iIdxCur);
- }
- }
-
- /* If this scan uses an index, make code substitutions to read data
- ** from the index in preference to the table. Sometimes, this means
- ** the table need never be read from. This is a performance boost,
- ** as the vdbe level waits until the table is read before actually
- ** seeking the table cursor to the record corresponding to the current
- ** position in the index.
- **
- ** Calls to the code generator in between sqlite3WhereBegin and
- ** sqlite3WhereEnd will have created code that references the table
- ** directly. This loop scans all that code looking for opcodes
- ** that reference the table and converts them into opcodes that
- ** reference the index.
- */
- if( (pLevel->plan.wsFlags & WHERE_INDEXED)!=0 && !db->mallocFailed){
- int k, j, last;
- VdbeOp *pOp;
- Index *pIdx = pLevel->plan.u.pIdx;
- int useIndexOnly = pLevel->plan.wsFlags & WHERE_IDX_ONLY;
-
- assert( pIdx!=0 );
- pOp = sqlite3VdbeGetOp(v, pWInfo->iTop);
- last = sqlite3VdbeCurrentAddr(v);
- for(k=pWInfo->iTop; k<last; k++, pOp++){
- if( pOp->p1!=pLevel->iTabCur ) continue;
- if( pOp->opcode==OP_Column ){
- for(j=0; j<pIdx->nColumn; j++){
- if( pOp->p2==pIdx->aiColumn[j] ){
- pOp->p2 = j;
- pOp->p1 = pLevel->iIdxCur;
- break;
- }
- }
- assert(!useIndexOnly || j<pIdx->nColumn);
- }else if( pOp->opcode==OP_Rowid ){
- pOp->p1 = pLevel->iIdxCur;
- pOp->opcode = OP_IdxRowid;
- }else if( pOp->opcode==OP_NullRow && useIndexOnly ){
- pOp->opcode = OP_Noop;
- }
- }
- }
- }
-
- /* Final cleanup
- */
- whereInfoFree(db, pWInfo);
- return;
-}
generated by cgit v1.1 at 2025-02-18 23:24:07 +0000