[sql] Recover Favicons v5 databases, with more recovery automation.

An entirely automated recovery system runs afoul of questions about
whether the corrupt database's schema can be trusted.
sql::Recovery::AutoRecoverTable() uses a schema created by the caller
to construct the recovery virtual table and then copies the data over.

sql::Recovery::SetupMeta() and GetMetaVersionNumber() simplify
accessing meta-table info in the corrupt database.

sql::test::IntegrityCheck() and CorruptSizeInHeader() helpers to
simplify common testing operations.

Rewrite ThumbnailDatabase v6 and v7 recovery code and tests using
these changes, and add a v5 recovery path.  Additionally handle
deprecated versions.

BUG=240396,109482

Review URL: https://codereview.chromium.org/50493012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235492 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 40 insertions, 0 deletions

diff --git a/sql/recovery.h b/sql/recovery.h
index be23e97..2475b0f 100644
--- a/sql/recovery.h
+++ b/sql/recovery.h
@@ -93,6 +93,46 @@ class SQL_EXPORT Recovery {
   // Handle to the temporary recovery database.
   sql::Connection* db() { return &recover_db_; }
 
+  // Attempt to recover the named table from the corrupt database into
+  // the recovery database using a temporary recover virtual table.
+  // The virtual table schema is derived from the named table's schema
+  // in database [main].  Data is copied using INSERT OR REPLACE, so
+  // duplicates overwrite each other.
+  //
+  // |extend_columns| allows recovering tables which have excess
+  // columns relative to the target schema.  The recover virtual table
+  // treats more data than specified as a sign of corruption.
+  //
+  // Returns true if all operations succeeded, with the number of rows
+  // recovered in |*rows_recovered|.
+  //
+  // NOTE(shess): Due to a flaw in the recovery virtual table, at this
+  // time this code injects the DEFAULT value of the target table in
+  // locations where the recovery table returns NULL.  This is not
+  // entirely correct, because it happens both when there is a short
+  // row (correct) but also where there is an actual NULL value
+  // (incorrect).
+  //
+  // TODO(shess): Flag for INSERT OR REPLACE vs IGNORE.
+  // TODO(shess): Handle extended table names.
+  bool AutoRecoverTable(const char* table_name,
+                        size_t extend_columns,
+                        size_t* rows_recovered);
+
+  // Setup a recover virtual table at temp.recover_meta, reading from
+  // corrupt.meta.  Returns true if created.
+  // TODO(shess): Perhaps integrate into Begin().
+  // TODO(shess): Add helpers to fetch additional items from the meta
+  // table as needed.
+  bool SetupMeta();
+
+  // Fetch the version number from temp.recover_meta.  Returns false
+  // if the query fails, or if there is no version row.  Otherwise
+  // returns true, with the version in |*version_number|.
+  //
+  // Only valid to call after successful SetupMeta().
+  bool GetMetaVersionNumber(int* version_number);
+
  private:
   explicit Recovery(Connection* connection);