Move app/sql/* files to sql/ directory.

I can't remove app/app.gyp and app/app_base.gypi yet because they are referenced
by third_party gyp files :(

BUG=72317
TEST=None

R=rsesek@chromium.org

move app/sql to sql

Review URL: http://codereview.chromium.org/7353026

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@93069 0039d316-1c4b-4281-b951-d872f2087c98

17 files changed, 2153 insertions, 15 deletions

diff --git a/sql/DEPS b/sql/DEPS
new file mode 100644
index 0000000..0f76c3a
--- /dev/null
+++ b/sql/DEPS
@@ -0,0 +1,3 @@
+include_rules = [
+  "+third_party/sqlite",
+]
diff --git a/sql/connection.cc b/sql/connection.cc
new file mode 100644
index 0000000..3f63301
--- /dev/null
+++ b/sql/connection.cc
@@ -0,0 +1,420 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "sql/connection.h"
+
+#include <string.h>
+
+#include "base/file_path.h"
+#include "base/logging.h"
+#include "base/string_util.h"
+#include "base/stringprintf.h"
+#include "base/utf_string_conversions.h"
+#include "sql/statement.h"
+#include "third_party/sqlite/sqlite3.h"
+
+namespace {
+
+// Spin for up to a second waiting for the lock to clear when setting
+// up the database.
+// TODO(shess): Better story on this.  http://crbug.com/56559
+const base::TimeDelta kBusyTimeout = base::TimeDelta::FromSeconds(1);
+
+class ScopedBusyTimeout {
+ public:
+  explicit ScopedBusyTimeout(sqlite3* db)
+      : db_(db) {
+  }
+  ~ScopedBusyTimeout() {
+    sqlite3_busy_timeout(db_, 0);
+  }
+
+  int SetTimeout(base::TimeDelta timeout) {
+    DCHECK_LT(timeout.InMilliseconds(), INT_MAX);
+    return sqlite3_busy_timeout(db_,
+                                static_cast<int>(timeout.InMilliseconds()));
+  }
+
+ private:
+  sqlite3* db_;
+};
+
+}  // namespace
+
+namespace sql {
+
+bool StatementID::operator<(const StatementID& other) const {
+  if (number_ != other.number_)
+    return number_ < other.number_;
+  return strcmp(str_, other.str_) < 0;
+}
+
+ErrorDelegate::ErrorDelegate() {
+}
+
+ErrorDelegate::~ErrorDelegate() {
+}
+
+Connection::StatementRef::StatementRef()
+    : connection_(NULL),
+      stmt_(NULL) {
+}
+
+Connection::StatementRef::StatementRef(Connection* connection,
+                                       sqlite3_stmt* stmt)
+    : connection_(connection),
+      stmt_(stmt) {
+  connection_->StatementRefCreated(this);
+}
+
+Connection::StatementRef::~StatementRef() {
+  if (connection_)
+    connection_->StatementRefDeleted(this);
+  Close();
+}
+
+void Connection::StatementRef::Close() {
+  if (stmt_) {
+    sqlite3_finalize(stmt_);
+    stmt_ = NULL;
+  }
+  connection_ = NULL;  // The connection may be getting deleted.
+}
+
+Connection::Connection()
+    : db_(NULL),
+      page_size_(0),
+      cache_size_(0),
+      exclusive_locking_(false),
+      transaction_nesting_(0),
+      needs_rollback_(false) {
+}
+
+Connection::~Connection() {
+  Close();
+}
+
+bool Connection::Open(const FilePath& path) {
+#if defined(OS_WIN)
+  return OpenInternal(WideToUTF8(path.value()));
+#elif defined(OS_POSIX)
+  return OpenInternal(path.value());
+#endif
+}
+
+bool Connection::OpenInMemory() {
+  return OpenInternal(":memory:");
+}
+
+void Connection::Close() {
+  statement_cache_.clear();
+  DCHECK(open_statements_.empty());
+  if (db_) {
+    sqlite3_close(db_);
+    db_ = NULL;
+  }
+}
+
+void Connection::Preload() {
+  if (!db_) {
+    NOTREACHED();
+    return;
+  }
+
+  // A statement must be open for the preload command to work. If the meta
+  // table doesn't exist, it probably means this is a new database and there
+  // is nothing to preload (so it's OK we do nothing).
+  if (!DoesTableExist("meta"))
+    return;
+  Statement dummy(GetUniqueStatement("SELECT * FROM meta"));
+  if (!dummy || !dummy.Step())
+    return;
+
+#if !defined(USE_SYSTEM_SQLITE)
+  // This function is only defined in Chromium's version of sqlite.
+  // Do not call it when using system sqlite.
+  sqlite3_preload(db_);
+#endif
+}
+
+bool Connection::BeginTransaction() {
+  if (needs_rollback_) {
+    DCHECK_GT(transaction_nesting_, 0);
+
+    // When we're going to rollback, fail on this begin and don't actually
+    // mark us as entering the nested transaction.
+    return false;
+  }
+
+  bool success = true;
+  if (!transaction_nesting_) {
+    needs_rollback_ = false;
+
+    Statement begin(GetCachedStatement(SQL_FROM_HERE, "BEGIN TRANSACTION"));
+    if (!begin || !begin.Run())
+      return false;
+  }
+  transaction_nesting_++;
+  return success;
+}
+
+void Connection::RollbackTransaction() {
+  if (!transaction_nesting_) {
+    NOTREACHED() << "Rolling back a nonexistent transaction";
+    return;
+  }
+
+  transaction_nesting_--;
+
+  if (transaction_nesting_ > 0) {
+    // Mark the outermost transaction as needing rollback.
+    needs_rollback_ = true;
+    return;
+  }
+
+  DoRollback();
+}
+
+bool Connection::CommitTransaction() {
+  if (!transaction_nesting_) {
+    NOTREACHED() << "Rolling back a nonexistent transaction";
+    return false;
+  }
+  transaction_nesting_--;
+
+  if (transaction_nesting_ > 0) {
+    // Mark any nested transactions as failing after we've already got one.
+    return !needs_rollback_;
+  }
+
+  if (needs_rollback_) {
+    DoRollback();
+    return false;
+  }
+
+  Statement commit(GetCachedStatement(SQL_FROM_HERE, "COMMIT"));
+  if (!commit)
+    return false;
+  return commit.Run();
+}
+
+bool Connection::Execute(const char* sql) {
+  if (!db_)
+    return false;
+  return sqlite3_exec(db_, sql, NULL, NULL, NULL) == SQLITE_OK;
+}
+
+bool Connection::ExecuteWithTimeout(const char* sql, base::TimeDelta timeout) {
+  if (!db_)
+    return false;
+
+  ScopedBusyTimeout busy_timeout(db_);
+  busy_timeout.SetTimeout(timeout);
+  return sqlite3_exec(db_, sql, NULL, NULL, NULL) == SQLITE_OK;
+}
+
+bool Connection::HasCachedStatement(const StatementID& id) const {
+  return statement_cache_.find(id) != statement_cache_.end();
+}
+
+scoped_refptr<Connection::StatementRef> Connection::GetCachedStatement(
+    const StatementID& id,
+    const char* sql) {
+  CachedStatementMap::iterator i = statement_cache_.find(id);
+  if (i != statement_cache_.end()) {
+    // Statement is in the cache. It should still be active (we're the only
+    // one invalidating cached statements, and we'll remove it from the cache
+    // if we do that. Make sure we reset it before giving out the cached one in
+    // case it still has some stuff bound.
+    DCHECK(i->second->is_valid());
+    sqlite3_reset(i->second->stmt());
+    return i->second;
+  }
+
+  scoped_refptr<StatementRef> statement = GetUniqueStatement(sql);
+  if (statement->is_valid())
+    statement_cache_[id] = statement;  // Only cache valid statements.
+  return statement;
+}
+
+scoped_refptr<Connection::StatementRef> Connection::GetUniqueStatement(
+    const char* sql) {
+  if (!db_)
+    return new StatementRef(this, NULL);  // Return inactive statement.
+
+  sqlite3_stmt* stmt = NULL;
+  if (sqlite3_prepare_v2(db_, sql, -1, &stmt, NULL) != SQLITE_OK) {
+    // Treat this as non-fatal, it can occur in a number of valid cases, and
+    // callers should be doing their own error handling.
+    DLOG(WARNING) << "SQL compile error " << GetErrorMessage();
+    return new StatementRef(this, NULL);
+  }
+  return new StatementRef(this, stmt);
+}
+
+bool Connection::DoesTableExist(const char* table_name) const {
+  // GetUniqueStatement can't be const since statements may modify the
+  // database, but we know ours doesn't modify it, so the cast is safe.
+  Statement statement(const_cast<Connection*>(this)->GetUniqueStatement(
+      "SELECT name FROM sqlite_master "
+      "WHERE type='table' AND name=?"));
+  if (!statement)
+    return false;
+  statement.BindString(0, table_name);
+  return statement.Step();  // Table exists if any row was returned.
+}
+
+bool Connection::DoesColumnExist(const char* table_name,
+                                 const char* column_name) const {
+  std::string sql("PRAGMA TABLE_INFO(");
+  sql.append(table_name);
+  sql.append(")");
+
+  // Our SQL is non-mutating, so this cast is OK.
+  Statement statement(const_cast<Connection*>(this)->GetUniqueStatement(
+      sql.c_str()));
+  if (!statement)
+    return false;
+
+  while (statement.Step()) {
+    if (!statement.ColumnString(1).compare(column_name))
+      return true;
+  }
+  return false;
+}
+
+int64 Connection::GetLastInsertRowId() const {
+  if (!db_) {
+    NOTREACHED();
+    return 0;
+  }
+  return sqlite3_last_insert_rowid(db_);
+}
+
+int Connection::GetLastChangeCount() const {
+  if (!db_) {
+    NOTREACHED();
+    return 0;
+  }
+  return sqlite3_changes(db_);
+}
+
+int Connection::GetErrorCode() const {
+  if (!db_)
+    return SQLITE_ERROR;
+  return sqlite3_errcode(db_);
+}
+
+int Connection::GetLastErrno() const {
+  if (!db_)
+    return -1;
+
+  int err = 0;
+  if (SQLITE_OK != sqlite3_file_control(db_, NULL, SQLITE_LAST_ERRNO, &err))
+    return -2;
+
+  return err;
+}
+
+const char* Connection::GetErrorMessage() const {
+  if (!db_)
+    return "sql::Connection has no connection.";
+  return sqlite3_errmsg(db_);
+}
+
+bool Connection::OpenInternal(const std::string& file_name) {
+  if (db_) {
+    NOTREACHED() << "sql::Connection is already open.";
+    return false;
+  }
+
+  int err = sqlite3_open(file_name.c_str(), &db_);
+  if (err != SQLITE_OK) {
+    OnSqliteError(err, NULL);
+    db_ = NULL;
+    return false;
+  }
+
+  // Enable extended result codes to provide more color on I/O errors.
+  // Not having extended result codes is not a fatal problem, as
+  // Chromium code does not attempt to handle I/O errors anyhow.  The
+  // current implementation always returns SQLITE_OK, the DCHECK is to
+  // quickly notify someone if SQLite changes.
+  err = sqlite3_extended_result_codes(db_, 1);
+  DCHECK_EQ(err, SQLITE_OK) << "Could not enable extended result codes";
+
+  // If indicated, lock up the database before doing anything else, so
+  // that the following code doesn't have to deal with locking.
+  // TODO(shess): This code is brittle.  Find the cases where code
+  // doesn't request |exclusive_locking_| and audit that it does the
+  // right thing with SQLITE_BUSY, and that it doesn't make
+  // assumptions about who might change things in the database.
+  // http://crbug.com/56559
+  if (exclusive_locking_) {
+    // TODO(shess): This should probably be a full CHECK().  Code
+    // which requests exclusive locking but doesn't get it is almost
+    // certain to be ill-tested.
+    if (!Execute("PRAGMA locking_mode=EXCLUSIVE"))
+      NOTREACHED() << "Could not set locking mode: " << GetErrorMessage();
+  }
+
+  if (page_size_ != 0) {
+    // Enforce SQLite restrictions on |page_size_|.
+    DCHECK(!(page_size_ & (page_size_ - 1)))
+        << " page_size_ " << page_size_ << " is not a power of two.";
+    static const int kSqliteMaxPageSize = 32768;  // from sqliteLimit.h
+    DCHECK_LE(page_size_, kSqliteMaxPageSize);
+    const std::string sql = StringPrintf("PRAGMA page_size=%d", page_size_);
+    if (!ExecuteWithTimeout(sql.c_str(), kBusyTimeout))
+      NOTREACHED() << "Could not set page size: " << GetErrorMessage();
+  }
+
+  if (cache_size_ != 0) {
+    const std::string sql = StringPrintf("PRAGMA cache_size=%d", cache_size_);
+    if (!ExecuteWithTimeout(sql.c_str(), kBusyTimeout))
+      NOTREACHED() << "Could not set cache size: " << GetErrorMessage();
+  }
+
+  return true;
+}
+
+void Connection::DoRollback() {
+  Statement rollback(GetCachedStatement(SQL_FROM_HERE, "ROLLBACK"));
+  if (rollback)
+    rollback.Run();
+}
+
+void Connection::StatementRefCreated(StatementRef* ref) {
+  DCHECK(open_statements_.find(ref) == open_statements_.end());
+  open_statements_.insert(ref);
+}
+
+void Connection::StatementRefDeleted(StatementRef* ref) {
+  StatementRefSet::iterator i = open_statements_.find(ref);
+  if (i == open_statements_.end())
+    NOTREACHED();
+  else
+    open_statements_.erase(i);
+}
+
+void Connection::ClearCache() {
+  statement_cache_.clear();
+
+  // The cache clear will get most statements. There may be still be references
+  // to some statements that are held by others (including one-shot statements).
+  // This will deactivate them so they can't be used again.
+  for (StatementRefSet::iterator i = open_statements_.begin();
+       i != open_statements_.end(); ++i)
+    (*i)->Close();
+}
+
+int Connection::OnSqliteError(int err, sql::Statement *stmt) {
+  if (error_delegate_.get())
+    return error_delegate_->OnError(err, this, stmt);
+  // The default handling is to assert on debug and to ignore on release.
+  NOTREACHED() << GetErrorMessage();
+  return err;
+}
+
+}  // namespace sql
diff --git a/sql/connection.h b/sql/connection.h
new file mode 100644
index 0000000..5807e36
--- /dev/null
+++ b/sql/connection.h
@@ -0,0 +1,387 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef SQL_CONNECTION_H_
+#define SQL_CONNECTION_H_
+#pragma once
+
+#include <map>
+#include <set>
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/memory/ref_counted.h"
+#include "base/time.h"
+
+class FilePath;
+struct sqlite3;
+struct sqlite3_stmt;
+
+namespace sql {
+
+class Statement;
+
+// Uniquely identifies a statement. There are two modes of operation:
+//
+// - In the most common mode, you will use the source file and line number to
+//   identify your statement. This is a convienient way to get uniqueness for
+//   a statement that is only used in one place. Use the SQL_FROM_HERE macro
+//   to generate a StatementID.
+//
+// - In the "custom" mode you may use the statement from different places or
+//   need to manage it yourself for whatever reason. In this case, you should
+//   make up your own unique name and pass it to the StatementID. This name
+//   must be a static string, since this object only deals with pointers and
+//   assumes the underlying string doesn't change or get deleted.
+//
+// This object is copyable and assignable using the compiler-generated
+// operator= and copy constructor.
+class StatementID {
+ public:
+  // Creates a uniquely named statement with the given file ane line number.
+  // Normally you will use SQL_FROM_HERE instead of calling yourself.
+  StatementID(const char* file, int line)
+      : number_(line),
+        str_(file) {
+  }
+
+  // Creates a uniquely named statement with the given user-defined name.
+  explicit StatementID(const char* unique_name)
+      : number_(-1),
+        str_(unique_name) {
+  }
+
+  // This constructor is unimplemented and will generate a linker error if
+  // called. It is intended to try to catch people dynamically generating
+  // a statement name that will be deallocated and will cause a crash later.
+  // All strings must be static and unchanging!
+  explicit StatementID(const std::string& dont_ever_do_this);
+
+  // We need this to insert into our map.
+  bool operator<(const StatementID& other) const;
+
+ private:
+  int number_;
+  const char* str_;
+};
+
+#define SQL_FROM_HERE sql::StatementID(__FILE__, __LINE__)
+
+class Connection;
+
+// ErrorDelegate defines the interface to implement error handling and recovery
+// for sqlite operations. This allows the rest of the classes to return true or
+// false while the actual error code and causing statement are delivered using
+// the OnError() callback.
+// The tipical usage is to centralize the code designed to handle database
+// corruption, low-level IO errors or locking violations.
+class ErrorDelegate : public base::RefCounted<ErrorDelegate> {
+ public:
+  ErrorDelegate();
+
+  // |error| is an sqlite result code as seen in sqlite\preprocessed\sqlite3.h
+  // |connection| is db connection where the error happened and |stmt| is
+  // our best guess at the statement that triggered the error.  Do not store
+  // these pointers.
+  //
+  // |stmt| MAY BE NULL if there is no statement causing the problem (i.e. on
+  // initialization).
+  //
+  // If the error condition has been fixed an the original statement succesfuly
+  // re-tried then returning SQLITE_OK is appropiate; otherwise is recomended
+  // that you return the original |error| or the appropiae error code.
+  virtual int OnError(int error, Connection* connection, Statement* stmt) = 0;
+
+ protected:
+  friend class base::RefCounted<ErrorDelegate>;
+
+  virtual ~ErrorDelegate();
+};
+
+class Connection {
+ private:
+  class StatementRef;  // Forward declaration, see real one below.
+
+ public:
+  // The database is opened by calling Open[InMemory](). Any uncommitted
+  // transactions will be rolled back when this object is deleted.
+  Connection();
+  ~Connection();
+
+  // Pre-init configuration ----------------------------------------------------
+
+  // Sets the page size that will be used when creating a new database. This
+  // must be called before Init(), and will only have an effect on new
+  // databases.
+  //
+  // From sqlite.org: "The page size must be a power of two greater than or
+  // equal to 512 and less than or equal to SQLITE_MAX_PAGE_SIZE. The maximum
+  // value for SQLITE_MAX_PAGE_SIZE is 32768."
+  void set_page_size(int page_size) { page_size_ = page_size; }
+
+  // Sets the number of pages that will be cached in memory by sqlite. The
+  // total cache size in bytes will be page_size * cache_size. This must be
+  // called before Open() to have an effect.
+  void set_cache_size(int cache_size) { cache_size_ = cache_size; }
+
+  // Call to put the database in exclusive locking mode. There is no "back to
+  // normal" flag because of some additional requirements sqlite puts on this
+  // transaition (requires another access to the DB) and because we don't
+  // actually need it.
+  //
+  // Exclusive mode means that the database is not unlocked at the end of each
+  // transaction, which means there may be less time spent initializing the
+  // next transaction because it doesn't have to re-aquire locks.
+  //
+  // This must be called before Open() to have an effect.
+  void set_exclusive_locking() { exclusive_locking_ = true; }
+
+  // Sets the object that will handle errors. Recomended that it should be set
+  // before calling Open(). If not set, the default is to ignore errors on
+  // release and assert on debug builds.
+  void set_error_delegate(ErrorDelegate* delegate) {
+    error_delegate_ = delegate;
+  }
+
+  // Initialization ------------------------------------------------------------
+
+  // Initializes the SQL connection for the given file, returning true if the
+  // file could be opened. You can call this or OpenInMemory.
+  bool Open(const FilePath& path);
+
+  // Initializes the SQL connection for a temporary in-memory database. There
+  // will be no associated file on disk, and the initial database will be
+  // empty. You can call this or Open.
+  bool OpenInMemory();
+
+  // Returns trie if the database has been successfully opened.
+  bool is_open() const { return !!db_; }
+
+  // Closes the database. This is automatically performed on destruction for
+  // you, but this allows you to close the database early. You must not call
+  // any other functions after closing it. It is permissable to call Close on
+  // an uninitialized or already-closed database.
+  void Close();
+
+  // Pre-loads the first <cache-size> pages into the cache from the file.
+  // If you expect to soon use a substantial portion of the database, this
+  // is much more efficient than allowing the pages to be populated organically
+  // since there is no per-page hard drive seeking. If the file is larger than
+  // the cache, the last part that doesn't fit in the cache will be brought in
+  // organically.
+  //
+  // This function assumes your class is using a meta table on the current
+  // database, as it openes a transaction on the meta table to force the
+  // database to be initialized. You should feel free to initialize the meta
+  // table after calling preload since the meta table will already be in the
+  // database if it exists, and if it doesn't exist, the database won't
+  // generally exist either.
+  void Preload();
+
+  // Transactions --------------------------------------------------------------
+
+  // Transaction management. We maintain a virtual transaction stack to emulate
+  // nested transactions since sqlite can't do nested transactions. The
+  // limitation is you can't roll back a sub transaction: if any transaction
+  // fails, all transactions open will also be rolled back. Any nested
+  // transactions after one has rolled back will return fail for Begin(). If
+  // Begin() fails, you must not call Commit or Rollback().
+  //
+  // Normally you should use sql::Transaction to manage a transaction, which
+  // will scope it to a C++ context.
+  bool BeginTransaction();
+  void RollbackTransaction();
+  bool CommitTransaction();
+
+  // Returns the current transaction nesting, which will be 0 if there are
+  // no open transactions.
+  int transaction_nesting() const { return transaction_nesting_; }
+
+  // Statements ----------------------------------------------------------------
+
+  // Executes the given SQL string, returning true on success. This is
+  // normally used for simple, 1-off statements that don't take any bound
+  // parameters and don't return any data (e.g. CREATE TABLE).
+  bool Execute(const char* sql);
+
+  // Returns true if we have a statement with the given identifier already
+  // cached. This is normally not necessary to call, but can be useful if the
+  // caller has to dynamically build up SQL to avoid doing so if it's already
+  // cached.
+  bool HasCachedStatement(const StatementID& id) const;
+
+  // Returns a statement for the given SQL using the statement cache. It can
+  // take a nontrivial amount of work to parse and compile a statement, so
+  // keeping commonly-used ones around for future use is important for
+  // performance.
+  //
+  // The SQL may have an error, so the caller must check validity of the
+  // statement before using it.
+  //
+  // The StatementID and the SQL must always correspond to one-another. The
+  // ID is the lookup into the cache, so crazy things will happen if you use
+  // different SQL with the same ID.
+  //
+  // You will normally use the SQL_FROM_HERE macro to generate a statement
+  // ID associated with the current line of code. This gives uniqueness without
+  // you having to manage unique names. See StatementID above for more.
+  //
+  // Example:
+  //   sql::Statement stmt(connection_.GetCachedStatement(
+  //       SQL_FROM_HERE, "SELECT * FROM foo"));
+  //   if (!stmt)
+  //     return false;  // Error creating statement.
+  scoped_refptr<StatementRef> GetCachedStatement(const StatementID& id,
+                                                 const char* sql);
+
+  // Returns a non-cached statement for the given SQL. Use this for SQL that
+  // is only executed once or only rarely (there is overhead associated with
+  // keeping a statement cached).
+  //
+  // See GetCachedStatement above for examples and error information.
+  scoped_refptr<StatementRef> GetUniqueStatement(const char* sql);
+
+  // Info querying -------------------------------------------------------------
+
+  // Returns true if the given table exists.
+  bool DoesTableExist(const char* table_name) const;
+
+  // Returns true if a column with the given name exists in the given table.
+  bool DoesColumnExist(const char* table_name, const char* column_name) const;
+
+  // Returns sqlite's internal ID for the last inserted row. Valid only
+  // immediately after an insert.
+  int64 GetLastInsertRowId() const;
+
+  // Returns sqlite's count of the number of rows modified by the last
+  // statement executed. Will be 0 if no statement has executed or the database
+  // is closed.
+  int GetLastChangeCount() const;
+
+  // Errors --------------------------------------------------------------------
+
+  // Returns the error code associated with the last sqlite operation.
+  int GetErrorCode() const;
+
+  // Returns the errno associated with GetErrorCode().  See
+  // SQLITE_LAST_ERRNO in SQLite documentation.
+  int GetLastErrno() const;
+
+  // Returns a pointer to a statically allocated string associated with the
+  // last sqlite operation.
+  const char* GetErrorMessage() const;
+
+ private:
+  // Statement access StatementRef which we don't want to expose to erverybody
+  // (they should go through Statement).
+  friend class Statement;
+
+  // Internal initialize function used by both Init and InitInMemory. The file
+  // name is always 8 bits since we want to use the 8-bit version of
+  // sqlite3_open. The string can also be sqlite's special ":memory:" string.
+  bool OpenInternal(const std::string& file_name);
+
+  // A StatementRef is a refcounted wrapper around a sqlite statement pointer.
+  // Refcounting allows us to give these statements out to sql::Statement
+  // objects while also optionally maintaining a cache of compiled statements
+  // by just keeping a refptr to these objects.
+  //
+  // A statement ref can be valid, in which case it can be used, or invalid to
+  // indicate that the statement hasn't been created yet, has an error, or has
+  // been destroyed.
+  //
+  // The Connection may revoke a StatementRef in some error cases, so callers
+  // should always check validity before using.
+  class StatementRef : public base::RefCounted<StatementRef> {
+   public:
+    // Default constructor initializes to an invalid statement.
+    StatementRef();
+    StatementRef(Connection* connection, sqlite3_stmt* stmt);
+
+    // When true, the statement can be used.
+    bool is_valid() const { return !!stmt_; }
+
+    // If we've not been linked to a connection, this will be NULL. Guaranteed
+    // non-NULL when is_valid().
+    Connection* connection() const { return connection_; }
+
+    // Returns the sqlite statement if any. If the statement is not active,
+    // this will return NULL.
+    sqlite3_stmt* stmt() const { return stmt_; }
+
+    // Destroys the compiled statement and marks it NULL. The statement will
+    // no longer be active.
+    void Close();
+
+   private:
+    friend class base::RefCounted<StatementRef>;
+
+    ~StatementRef();
+
+    Connection* connection_;
+    sqlite3_stmt* stmt_;
+
+    DISALLOW_COPY_AND_ASSIGN(StatementRef);
+  };
+  friend class StatementRef;
+
+  // Executes a rollback statement, ignoring all transaction state. Used
+  // internally in the transaction management code.
+  void DoRollback();
+
+  // Called by a StatementRef when it's being created or destroyed. See
+  // open_statements_ below.
+  void StatementRefCreated(StatementRef* ref);
+  void StatementRefDeleted(StatementRef* ref);
+
+  // Frees all cached statements from statement_cache_.
+  void ClearCache();
+
+  // Called by Statement objects when an sqlite function returns an error.
+  // The return value is the error code reflected back to client code.
+  int OnSqliteError(int err, Statement* stmt);
+
+  // Like |Execute()|, but retries if the database is locked.
+  bool ExecuteWithTimeout(const char* sql, base::TimeDelta ms_timeout);
+
+  // The actual sqlite database. Will be NULL before Init has been called or if
+  // Init resulted in an error.
+  sqlite3* db_;
+
+  // Parameters we'll configure in sqlite before doing anything else. Zero means
+  // use the default value.
+  int page_size_;
+  int cache_size_;
+  bool exclusive_locking_;
+
+  // All cached statements. Keeping a reference to these statements means that
+  // they'll remain active.
+  typedef std::map<StatementID, scoped_refptr<StatementRef> >
+      CachedStatementMap;
+  CachedStatementMap statement_cache_;
+
+  // A list of all StatementRefs we've given out. Each ref must register with
+  // us when it's created or destroyed. This allows us to potentially close
+  // any open statements when we encounter an error.
+  typedef std::set<StatementRef*> StatementRefSet;
+  StatementRefSet open_statements_;
+
+  // Number of currently-nested transactions.
+  int transaction_nesting_;
+
+  // True if any of the currently nested transactions have been rolled back.
+  // When we get to the outermost transaction, this will determine if we do
+  // a rollback instead of a commit.
+  bool needs_rollback_;
+
+  // This object handles errors resulting from all forms of executing sqlite
+  // commands or statements. It can be null which means default handling.
+  scoped_refptr<ErrorDelegate> error_delegate_;
+
+  DISALLOW_COPY_AND_ASSIGN(Connection);
+};
+
+}  // namespace sql
+
+#endif  // SQL_CONNECTION_H_
diff --git a/sql/connection_unittest.cc b/sql/connection_unittest.cc
new file mode 100644
index 0000000..e99bff7
--- /dev/null
+++ b/sql/connection_unittest.cc
@@ -0,0 +1,106 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/file_util.h"
+#include "base/scoped_temp_dir.h"
+#include "sql/connection.h"
+#include "sql/statement.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "third_party/sqlite/sqlite3.h"
+
+class SQLConnectionTest : public testing::Test {
+ public:
+  SQLConnectionTest() {}
+
+  void SetUp() {
+    ASSERT_TRUE(temp_dir_.CreateUniqueTempDir());
+    ASSERT_TRUE(db_.Open(temp_dir_.path().AppendASCII("SQLConnectionTest.db")));
+  }
+
+  void TearDown() {
+    db_.Close();
+  }
+
+  sql::Connection& db() { return db_; }
+
+ private:
+  ScopedTempDir temp_dir_;
+  sql::Connection db_;
+};
+
+TEST_F(SQLConnectionTest, Execute) {
+  // Valid statement should return true.
+  ASSERT_TRUE(db().Execute("CREATE TABLE foo (a, b)"));
+  EXPECT_EQ(SQLITE_OK, db().GetErrorCode());
+
+  // Invalid statement should fail.
+  ASSERT_FALSE(db().Execute("CREATE TAB foo (a, b"));
+  EXPECT_EQ(SQLITE_ERROR, db().GetErrorCode());
+}
+
+TEST_F(SQLConnectionTest, CachedStatement) {
+  sql::StatementID id1("foo", 12);
+
+  ASSERT_TRUE(db().Execute("CREATE TABLE foo (a, b)"));
+  ASSERT_TRUE(db().Execute("INSERT INTO foo(a, b) VALUES (12, 13)"));
+
+  // Create a new cached statement.
+  {
+    sql::Statement s(db().GetCachedStatement(id1, "SELECT a FROM foo"));
+    ASSERT_FALSE(!s);  // Test ! operator for validity.
+
+    ASSERT_TRUE(s.Step());
+    EXPECT_EQ(12, s.ColumnInt(0));
+  }
+
+  // The statement should be cached still.
+  EXPECT_TRUE(db().HasCachedStatement(id1));
+
+  {
+    // Get the same statement using different SQL. This should ignore our
+    // SQL and use the cached one (so it will be valid).
+    sql::Statement s(db().GetCachedStatement(id1, "something invalid("));
+    ASSERT_FALSE(!s);  // Test ! operator for validity.
+
+    ASSERT_TRUE(s.Step());
+    EXPECT_EQ(12, s.ColumnInt(0));
+  }
+
+  // Make sure other statements aren't marked as cached.
+  EXPECT_FALSE(db().HasCachedStatement(SQL_FROM_HERE));
+}
+
+TEST_F(SQLConnectionTest, DoesStuffExist) {
+  // Test DoesTableExist.
+  EXPECT_FALSE(db().DoesTableExist("foo"));
+  ASSERT_TRUE(db().Execute("CREATE TABLE foo (a, b)"));
+  EXPECT_TRUE(db().DoesTableExist("foo"));
+
+  // Should be case sensitive.
+  EXPECT_FALSE(db().DoesTableExist("FOO"));
+
+  // Test DoesColumnExist.
+  EXPECT_FALSE(db().DoesColumnExist("foo", "bar"));
+  EXPECT_TRUE(db().DoesColumnExist("foo", "a"));
+
+  // Testing for a column on a nonexistent table.
+  EXPECT_FALSE(db().DoesColumnExist("bar", "b"));
+}
+
+TEST_F(SQLConnectionTest, GetLastInsertRowId) {
+  ASSERT_TRUE(db().Execute("CREATE TABLE foo (id INTEGER PRIMARY KEY, value)"));
+
+  ASSERT_TRUE(db().Execute("INSERT INTO foo (value) VALUES (12)"));
+
+  // Last insert row ID should be valid.
+  int64 row = db().GetLastInsertRowId();
+  EXPECT_LT(0, row);
+
+  // It should be the primary key of the row we just inserted.
+  sql::Statement s(db().GetUniqueStatement("SELECT value FROM foo WHERE id=?"));
+  s.BindInt64(0, row);
+  ASSERT_TRUE(s.Step());
+  EXPECT_EQ(12, s.ColumnInt(0));
+}
+
diff --git a/sql/diagnostic_error_delegate.h b/sql/diagnostic_error_delegate.h
new file mode 100644
index 0000000..70677bd
--- /dev/null
+++ b/sql/diagnostic_error_delegate.h
@@ -0,0 +1,50 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef SQL_DIAGNOSTIC_ERROR_DELEGATE_H_
+#define SQL_DIAGNOSTIC_ERROR_DELEGATE_H_
+#pragma once
+
+#include "base/logging.h"
+#include "base/metrics/histogram.h"
+#include "sql/connection.h"
+
+namespace sql {
+
+// This class handles the exceptional sqlite errors that we might encounter
+// if for example the db is corrupted. Right now we just generate a UMA
+// histogram for release and an assert for debug builds.
+//
+// Why is it a template you ask? well, that is a funny story. The histograms
+// need to be singletons that is why they are always static at the function
+// scope, but we cannot use the Singleton class because they are not default
+// constructible. The template parameter makes the compiler to create unique
+// classes that don't share the same static variable.
+template <class UniqueT>
+class DiagnosticErrorDelegate : public ErrorDelegate {
+ public:
+
+  virtual int OnError(int error, Connection* connection,
+                      Statement* stmt) {
+    NOTREACHED() << "sqlite error " << error
+                 << ", errno " << connection->GetLastErrno()
+                 << ": " << connection->GetErrorMessage();
+    RecordErrorInHistogram(error);
+    return error;
+  }
+
+ private:
+  static void RecordErrorInHistogram(int error) {
+    // Trim off the extended error codes.
+    error &= 0xff;
+
+    // The histogram values from sqlite result codes go currently from 1 to
+    // 26 currently but 50 gives them room to grow.
+    UMA_HISTOGRAM_ENUMERATION(UniqueT::name(), error, 50);
+  }
+};
+
+}  // namespace sql
+
+#endif  // SQL_DIAGNOSTIC_ERROR_DELEGATE_H_
diff --git a/sql/init_status.h b/sql/init_status.h
new file mode 100644
index 0000000..b9f87e0
--- /dev/null
+++ b/sql/init_status.h
@@ -0,0 +1,24 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef APP_SQL_INIT_STATUS_H_
+#define APP_SQL_INIT_STATUS_H_
+#pragma once
+
+namespace sql {
+
+// Used as the return value for some databases' init functions.
+enum InitStatus {
+  INIT_OK,
+
+  // Some error, usually I/O related opening the file.
+  INIT_FAILURE,
+
+  // The database is from a future version of the app and cannot be read.
+  INIT_TOO_NEW,
+};
+
+}  // namespace sql
+
+#endif  // APP_SQL_INIT_STATUS_H_
diff --git a/sql/meta_table.cc b/sql/meta_table.cc
new file mode 100644
index 0000000..c4736ef
--- /dev/null
+++ b/sql/meta_table.cc
@@ -0,0 +1,152 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "sql/meta_table.h"
+
+#include "base/logging.h"
+#include "base/string_util.h"
+#include "sql/connection.h"
+#include "sql/statement.h"
+
+namespace sql {
+
+// Key used in our meta table for version numbers.
+static const char kVersionKey[] = "version";
+static const char kCompatibleVersionKey[] = "last_compatible_version";
+
+MetaTable::MetaTable() : db_(NULL) {
+}
+
+MetaTable::~MetaTable() {
+}
+
+// static
+bool MetaTable::DoesTableExist(sql::Connection* db) {
+  DCHECK(db);
+  return db->DoesTableExist("meta");
+}
+
+bool MetaTable::Init(Connection* db, int version, int compatible_version) {
+  DCHECK(!db_ && db);
+  db_ = db;
+  if (!DoesTableExist(db)) {
+    if (!db_->Execute("CREATE TABLE meta"
+        "(key LONGVARCHAR NOT NULL UNIQUE PRIMARY KEY,"
+         "value LONGVARCHAR)"))
+      return false;
+
+    // Note: there is no index over the meta table. We currently only have a
+    // couple of keys, so it doesn't matter. If we start storing more stuff in
+    // there, we should create an index.
+    SetVersionNumber(version);
+    SetCompatibleVersionNumber(compatible_version);
+  }
+  return true;
+}
+
+void MetaTable::Reset() {
+  db_ = NULL;
+}
+
+bool MetaTable::SetValue(const char* key, const std::string& value) {
+  Statement s;
+  if (!PrepareSetStatement(&s, key))
+    return false;
+  s.BindString(1, value);
+  return s.Run();
+}
+
+bool MetaTable::GetValue(const char* key, std::string* value) {
+  Statement s;
+  if (!PrepareGetStatement(&s, key))
+    return false;
+
+  *value = s.ColumnString(0);
+  return true;
+}
+
+bool MetaTable::SetValue(const char* key, int value) {
+  Statement s;
+  if (!PrepareSetStatement(&s, key))
+    return false;
+
+  s.BindInt(1, value);
+  return s.Run();
+}
+
+bool MetaTable::GetValue(const char* key, int* value) {
+  Statement s;
+  if (!PrepareGetStatement(&s, key))
+    return false;
+
+  *value = s.ColumnInt(0);
+  return true;
+}
+
+bool MetaTable::SetValue(const char* key, int64 value) {
+  Statement s;
+  if (!PrepareSetStatement(&s, key))
+    return false;
+  s.BindInt64(1, value);
+  return s.Run();
+}
+
+bool MetaTable::GetValue(const char* key, int64* value) {
+  Statement s;
+  if (!PrepareGetStatement(&s, key))
+    return false;
+
+  *value = s.ColumnInt64(0);
+  return true;
+}
+
+void MetaTable::SetVersionNumber(int version) {
+  SetValue(kVersionKey, version);
+}
+
+int MetaTable::GetVersionNumber() {
+  int version = 0;
+  if (!GetValue(kVersionKey, &version))
+    return 0;
+  return version;
+}
+
+void MetaTable::SetCompatibleVersionNumber(int version) {
+  SetValue(kCompatibleVersionKey, version);
+}
+
+int MetaTable::GetCompatibleVersionNumber() {
+  int version = 0;
+  if (!GetValue(kCompatibleVersionKey, &version))
+    return 0;
+  return version;
+}
+
+bool MetaTable::PrepareSetStatement(Statement* statement, const char* key) {
+  DCHECK(db_ && statement);
+  statement->Assign(db_->GetCachedStatement(SQL_FROM_HERE,
+      "INSERT OR REPLACE INTO meta (key,value) VALUES (?,?)"));
+  if (!statement->is_valid()) {
+    NOTREACHED() << db_->GetErrorMessage();
+    return false;
+  }
+  statement->BindCString(0, key);
+  return true;
+}
+
+bool MetaTable::PrepareGetStatement(Statement* statement, const char* key) {
+  DCHECK(db_ && statement);
+  statement->Assign(db_->GetCachedStatement(SQL_FROM_HERE,
+      "SELECT value FROM meta WHERE key=?"));
+  if (!statement->is_valid()) {
+    NOTREACHED() << db_->GetErrorMessage();
+    return false;
+  }
+  statement->BindCString(0, key);
+  if (!statement->Step())
+    return false;
+  return true;
+}
+
+}  // namespace sql
diff --git a/sql/meta_table.h b/sql/meta_table.h
new file mode 100644
index 0000000..4a640d8
--- /dev/null
+++ b/sql/meta_table.h
@@ -0,0 +1,83 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef SQL_META_TABLE_H_
+#define SQL_META_TABLE_H_
+#pragma once
+
+#include <string>
+
+#include "base/basictypes.h"
+
+namespace sql {
+
+class Connection;
+class Statement;
+
+class MetaTable {
+ public:
+  MetaTable();
+  ~MetaTable();
+
+  // Returns true if the 'meta' table exists.
+  static bool DoesTableExist(Connection* db);
+
+  // Initializes the MetaTableHelper, creating the meta table if necessary. For
+  // new tables, it will initialize the version number to |version| and the
+  // compatible version number to |compatible_version|.
+  bool Init(Connection* db, int version, int compatible_version);
+
+  // Resets this MetaTable object, making another call to Init() possible.
+  void Reset();
+
+  // The version number of the database. This should be the version number of
+  // the creator of the file. The version number will be 0 if there is no
+  // previously set version number.
+  //
+  // See also Get/SetCompatibleVersionNumber().
+  void SetVersionNumber(int version);
+  int GetVersionNumber();
+
+  // The compatible version number is the lowest version of the code that this
+  // database can be read by. If there are minor changes or additions, old
+  // versions of the code can still work with the database without failing.
+  //
+  // For example, if an optional column is added to a table in version 3, the
+  // new code will set the version to 3, and the compatible version to 2, since
+  // the code expecting version 2 databases can still read and write the table.
+  //
+  // Rule of thumb: check the version number when you're upgrading, but check
+  // the compatible version number to see if you can read the file at all. If
+  // it's larger than you code is expecting, fail.
+  //
+  // The compatible version number will be 0 if there is no previously set
+  // compatible version number.
+  void SetCompatibleVersionNumber(int version);
+  int GetCompatibleVersionNumber();
+
+  // Set the given arbitrary key with the given data. Returns true on success.
+  bool SetValue(const char* key, const std::string& value);
+  bool SetValue(const char* key, int value);
+  bool SetValue(const char* key, int64 value);
+
+  // Retrieves the value associated with the given key. This will use sqlite's
+  // type conversion rules. It will return true on success.
+  bool GetValue(const char* key, std::string* value);
+  bool GetValue(const char* key, int* value);
+  bool GetValue(const char* key, int64* value);
+
+ private:
+  // Conveniences to prepare the two types of statements used by
+  // MetaTableHelper.
+  bool PrepareSetStatement(Statement* statement, const char* key);
+  bool PrepareGetStatement(Statement* statement, const char* key);
+
+  Connection* db_;
+
+  DISALLOW_COPY_AND_ASSIGN(MetaTable);
+};
+
+}  // namespace sql
+
+#endif  // SQL_META_TABLE_H_
diff --git a/sql/run_all_unittests.cc b/sql/run_all_unittests.cc
new file mode 100644
index 0000000..7fd6ef2
--- /dev/null
+++ b/sql/run_all_unittests.cc
@@ -0,0 +1,9 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/test/test_suite.h"
+
+int main(int argc, char** argv) {
+  return base::TestSuite(argc, argv).Run();
+}
diff --git a/sql/sql.gyp b/sql/sql.gyp
index e5681ce..ac87444 100644
--- a/sql/sql.gyp
+++ b/sql/sql.gyp
@@ -15,16 +15,16 @@
         '../third_party/sqlite/sqlite.gyp:sqlite',
       ],
       'sources': [
-        '../app/sql/connection.cc',
-        '../app/sql/connection.h',
-        '../app/sql/diagnostic_error_delegate.h',
-        '../app/sql/init_status.h',
-        '../app/sql/meta_table.cc',
-        '../app/sql/meta_table.h',
-        '../app/sql/statement.cc',
-        '../app/sql/statement.h',
-        '../app/sql/transaction.cc',
-        '../app/sql/transaction.h',
+        'connection.cc',
+        'connection.h',
+        'diagnostic_error_delegate.h',
+        'init_status.h',
+        'meta_table.cc',
+        'meta_table.h',
+        'statement.cc',
+        'statement.h',
+        'transaction.cc',
+        'transaction.h',
       ],
     },
     {
@@ -36,11 +36,11 @@
         '../testing/gtest.gyp:gtest',
       ],
       'sources': [
-        '../app/run_all_unittests.cc',
-        '../app/sql/connection_unittest.cc',
-        '../app/sql/sqlite_features_unittest.cc',
-        '../app/sql/statement_unittest.cc',
-        '../app/sql/transaction_unittest.cc',
+        'run_all_unittests.cc',
+        'connection_unittest.cc',
+        'sqlite_features_unittest.cc',
+        'statement_unittest.cc',
+        'transaction_unittest.cc',
       ],
       'include_dirs': [
         '..',
diff --git a/sql/sqlite_features_unittest.cc b/sql/sqlite_features_unittest.cc
new file mode 100644
index 0000000..a25413d
--- /dev/null
+++ b/sql/sqlite_features_unittest.cc
@@ -0,0 +1,100 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <string>
+
+#include "base/file_path.h"
+#include "base/file_util.h"
+#include "base/path_service.h"
+#include "sql/connection.h"
+#include "sql/statement.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "third_party/sqlite/sqlite3.h"
+
+// Test that certain features are/are-not enabled in our SQLite.
+
+namespace {
+
+
+class StatementErrorHandler : public sql::ErrorDelegate {
+ public:
+  StatementErrorHandler() : error_(SQLITE_OK) {}
+
+  virtual int OnError(int error, sql::Connection* connection,
+                      sql::Statement* stmt) {
+    error_ = error;
+    const char* sql_txt = stmt ? stmt->GetSQLStatement() : NULL;
+    sql_text_ = sql_txt ? sql_txt : "no statement available";
+    return error;
+  }
+
+  int error() const { return error_; }
+
+  void reset_error() {
+    sql_text_.clear();
+    error_ = SQLITE_OK;
+  }
+
+  const char* sql_statement() const { return sql_text_.c_str(); }
+
+ private:
+  int error_;
+  std::string sql_text_;
+};
+
+class SQLiteFeaturesTest : public testing::Test {
+ public:
+  SQLiteFeaturesTest() : error_handler_(new StatementErrorHandler) {}
+
+  void SetUp() {
+    ASSERT_TRUE(PathService::Get(base::DIR_TEMP, &path_));
+    path_ = path_.AppendASCII("SQLStatementTest.db");
+    file_util::Delete(path_, false);
+    ASSERT_TRUE(db_.Open(path_));
+    // The |error_handler_| will be called if any sqlite statement operation
+    // returns an error code.
+    db_.set_error_delegate(error_handler_);
+  }
+
+  void TearDown() {
+    // If any error happened the original sql statement can be found in
+    // error_handler_->sql_statement().
+    EXPECT_EQ(SQLITE_OK, error_handler_->error());
+    db_.Close();
+    // If this fails something is going on with cleanup and later tests may
+    // fail, so we want to identify problems right away.
+    ASSERT_TRUE(file_util::Delete(path_, false));
+  }
+
+  sql::Connection& db() { return db_; }
+
+  int sqlite_error() const { return error_handler_->error(); }
+  void reset_error() const { error_handler_->reset_error(); }
+
+ private:
+  FilePath path_;
+  sql::Connection db_;
+  scoped_refptr<StatementErrorHandler> error_handler_;
+};
+
+// Do not include fts1 support, it is not useful, and nobody is
+// looking at it.
+TEST_F(SQLiteFeaturesTest, NoFTS1) {
+  ASSERT_FALSE(db().Execute("CREATE VIRTUAL TABLE foo USING fts1(x)"));
+}
+
+// fts2 is used for older history files, so we're signed on for
+// keeping our version up-to-date.
+// TODO(shess): Think up a crazy way to get out from having to support
+// this forever.
+TEST_F(SQLiteFeaturesTest, FTS2) {
+  ASSERT_TRUE(db().Execute("CREATE VIRTUAL TABLE foo USING fts2(x)"));
+}
+
+// fts3 is used for current history files, and also for WebDatabase.
+TEST_F(SQLiteFeaturesTest, FTS3) {
+  ASSERT_TRUE(db().Execute("CREATE VIRTUAL TABLE foo USING fts3(x)"));
+}
+
+}  // namespace
diff --git a/sql/statement.cc b/sql/statement.cc
new file mode 100644
index 0000000..8f75693
--- /dev/null
+++ b/sql/statement.cc
@@ -0,0 +1,270 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "sql/statement.h"
+
+#include "base/logging.h"
+#include "base/utf_string_conversions.h"
+#include "third_party/sqlite/sqlite3.h"
+
+namespace sql {
+
+// This empty constructor initializes our reference with an empty one so that
+// we don't have to NULL-check the ref_ to see if the statement is valid: we
+// only have to check the ref's validity bit.
+Statement::Statement()
+    : ref_(new Connection::StatementRef),
+      succeeded_(false) {
+}
+
+Statement::Statement(scoped_refptr<Connection::StatementRef> ref)
+    : ref_(ref),
+      succeeded_(false) {
+}
+
+Statement::~Statement() {
+  // Free the resources associated with this statement. We assume there's only
+  // one statement active for a given sqlite3_stmt at any time, so this won't
+  // mess with anything.
+  Reset();
+}
+
+void Statement::Assign(scoped_refptr<Connection::StatementRef> ref) {
+  Reset();
+  ref_ = ref;
+}
+
+bool Statement::Run() {
+  if (!is_valid())
+    return false;
+  return CheckError(sqlite3_step(ref_->stmt())) == SQLITE_DONE;
+}
+
+bool Statement::Step() {
+  if (!is_valid())
+    return false;
+  return CheckError(sqlite3_step(ref_->stmt())) == SQLITE_ROW;
+}
+
+void Statement::Reset() {
+  if (is_valid()) {
+    // We don't call CheckError() here because sqlite3_reset() returns
+    // the last error that Step() caused thereby generating a second
+    // spurious error callback.
+    sqlite3_clear_bindings(ref_->stmt());
+    sqlite3_reset(ref_->stmt());
+  }
+  succeeded_ = false;
+}
+
+bool Statement::Succeeded() const {
+  if (!is_valid())
+    return false;
+  return succeeded_;
+}
+
+bool Statement::BindNull(int col) {
+  if (is_valid()) {
+    int err = CheckError(sqlite3_bind_null(ref_->stmt(), col + 1));
+    return err == SQLITE_OK;
+  }
+  return false;
+}
+
+bool Statement::BindBool(int col, bool val) {
+  return BindInt(col, val ? 1 : 0);
+}
+
+bool Statement::BindInt(int col, int val) {
+  if (is_valid()) {
+    int err = CheckError(sqlite3_bind_int(ref_->stmt(), col + 1, val));
+    return err == SQLITE_OK;
+  }
+  return false;
+}
+
+bool Statement::BindInt64(int col, int64 val) {
+  if (is_valid()) {
+    int err = CheckError(sqlite3_bind_int64(ref_->stmt(), col + 1, val));
+    return err == SQLITE_OK;
+  }
+  return false;
+}
+
+bool Statement::BindDouble(int col, double val) {
+  if (is_valid()) {
+    int err = CheckError(sqlite3_bind_double(ref_->stmt(), col + 1, val));
+    return err == SQLITE_OK;
+  }
+  return false;
+}
+
+bool Statement::BindCString(int col, const char* val) {
+  if (is_valid()) {
+    int err = CheckError(sqlite3_bind_text(ref_->stmt(), col + 1, val, -1,
+                         SQLITE_TRANSIENT));
+    return err == SQLITE_OK;
+  }
+  return false;
+}
+
+bool Statement::BindString(int col, const std::string& val) {
+  if (is_valid()) {
+    int err = CheckError(sqlite3_bind_text(ref_->stmt(), col + 1, val.data(),
+                                           val.size(), SQLITE_TRANSIENT));
+    return err == SQLITE_OK;
+  }
+  return false;
+}
+
+bool Statement::BindString16(int col, const string16& value) {
+  return BindString(col, UTF16ToUTF8(value));
+}
+
+bool Statement::BindBlob(int col, const void* val, int val_len) {
+  if (is_valid()) {
+    int err = CheckError(sqlite3_bind_blob(ref_->stmt(), col + 1,
+                         val, val_len, SQLITE_TRANSIENT));
+    return err == SQLITE_OK;
+  }
+  return false;
+}
+
+int Statement::ColumnCount() const {
+  if (!is_valid()) {
+    NOTREACHED();
+    return 0;
+  }
+  return sqlite3_column_count(ref_->stmt());
+}
+
+ColType Statement::ColumnType(int col) const {
+  // Verify that our enum matches sqlite's values.
+  COMPILE_ASSERT(COLUMN_TYPE_INTEGER == SQLITE_INTEGER, integer_no_match);
+  COMPILE_ASSERT(COLUMN_TYPE_FLOAT == SQLITE_FLOAT, float_no_match);
+  COMPILE_ASSERT(COLUMN_TYPE_TEXT == SQLITE_TEXT, integer_no_match);
+  COMPILE_ASSERT(COLUMN_TYPE_BLOB == SQLITE_BLOB, blob_no_match);
+  COMPILE_ASSERT(COLUMN_TYPE_NULL == SQLITE_NULL, null_no_match);
+
+  return static_cast<ColType>(sqlite3_column_type(ref_->stmt(), col));
+}
+
+bool Statement::ColumnBool(int col) const {
+  return !!ColumnInt(col);
+}
+
+int Statement::ColumnInt(int col) const {
+  if (!is_valid()) {
+    NOTREACHED();
+    return 0;
+  }
+  return sqlite3_column_int(ref_->stmt(), col);
+}
+
+int64 Statement::ColumnInt64(int col) const {
+  if (!is_valid()) {
+    NOTREACHED();
+    return 0;
+  }
+  return sqlite3_column_int64(ref_->stmt(), col);
+}
+
+double Statement::ColumnDouble(int col) const {
+  if (!is_valid()) {
+    NOTREACHED();
+    return 0;
+  }
+  return sqlite3_column_double(ref_->stmt(), col);
+}
+
+std::string Statement::ColumnString(int col) const {
+  if (!is_valid()) {
+    NOTREACHED();
+    return "";
+  }
+  const char* str = reinterpret_cast<const char*>(
+      sqlite3_column_text(ref_->stmt(), col));
+  int len = sqlite3_column_bytes(ref_->stmt(), col);
+
+  std::string result;
+  if (str && len > 0)
+    result.assign(str, len);
+  return result;
+}
+
+string16 Statement::ColumnString16(int col) const {
+  if (!is_valid()) {
+    NOTREACHED();
+    return string16();
+  }
+  std::string s = ColumnString(col);
+  return !s.empty() ? UTF8ToUTF16(s) : string16();
+}
+
+int Statement::ColumnByteLength(int col) const {
+  if (!is_valid()) {
+    NOTREACHED();
+    return 0;
+  }
+  return sqlite3_column_bytes(ref_->stmt(), col);
+}
+
+const void* Statement::ColumnBlob(int col) const {
+  if (!is_valid()) {
+    NOTREACHED();
+    return NULL;
+  }
+
+  return sqlite3_column_blob(ref_->stmt(), col);
+}
+
+bool Statement::ColumnBlobAsString(int col, std::string* blob) {
+  if (!is_valid()) {
+    NOTREACHED();
+    return false;
+  }
+  const void* p = ColumnBlob(col);
+  size_t len = ColumnByteLength(col);
+  blob->resize(len);
+  if (blob->size() != len) {
+    return false;
+  }
+  blob->assign(reinterpret_cast<const char*>(p), len);
+  return true;
+}
+
+void Statement::ColumnBlobAsVector(int col, std::vector<char>* val) const {
+  val->clear();
+  if (!is_valid()) {
+    NOTREACHED();
+    return;
+  }
+
+  const void* data = sqlite3_column_blob(ref_->stmt(), col);
+  int len = sqlite3_column_bytes(ref_->stmt(), col);
+  if (data && len > 0) {
+    val->resize(len);
+    memcpy(&(*val)[0], data, len);
+  }
+}
+
+void Statement::ColumnBlobAsVector(
+    int col,
+    std::vector<unsigned char>* val) const {
+  ColumnBlobAsVector(col, reinterpret_cast< std::vector<char>* >(val));
+}
+
+const char* Statement::GetSQLStatement() {
+  return sqlite3_sql(ref_->stmt());
+}
+
+int Statement::CheckError(int err) {
+  // Please don't add DCHECKs here, OnSqliteError() already has them.
+  succeeded_ = (err == SQLITE_OK || err == SQLITE_ROW || err == SQLITE_DONE);
+  if (!succeeded_ && is_valid())
+    return ref_->connection()->OnSqliteError(err, this);
+  return err;
+}
+
+}  // namespace sql
diff --git a/sql/statement.h b/sql/statement.h
new file mode 100644
index 0000000..dbb96713
--- /dev/null
+++ b/sql/statement.h
@@ -0,0 +1,167 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef SQL_STATEMENT_H_
+#define SQL_STATEMENT_H_
+#pragma once
+
+#include <string>
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/memory/ref_counted.h"
+#include "base/string16.h"
+#include "sql/connection.h"
+
+namespace sql {
+
+// Possible return values from ColumnType in a statement. These should match
+// the values in sqlite3.h.
+enum ColType {
+  COLUMN_TYPE_INTEGER = 1,
+  COLUMN_TYPE_FLOAT = 2,
+  COLUMN_TYPE_TEXT = 3,
+  COLUMN_TYPE_BLOB = 4,
+  COLUMN_TYPE_NULL = 5,
+};
+
+// Normal usage:
+//   sql::Statement s(connection_.GetUniqueStatement(...));
+//   if (!s)  // You should check for errors before using the statement.
+//     return false;
+//
+//   s.BindInt(0, a);
+//   if (s.Step())
+//     return s.ColumnString(0);
+//
+// Step() and Run() just return true to signal success. If you want to handle
+// specific errors such as database corruption, install an error handler in
+// in the connection object using set_error_delegate().
+class Statement {
+ public:
+  // Creates an uninitialized statement. The statement will be invalid until
+  // you initialize it via Assign.
+  Statement();
+
+  explicit Statement(scoped_refptr<Connection::StatementRef> ref);
+  ~Statement();
+
+  // Initializes this object with the given statement, which may or may not
+  // be valid. Use is_valid() to check if it's OK.
+  void Assign(scoped_refptr<Connection::StatementRef> ref);
+
+  // Returns true if the statement can be executed. All functions can still
+  // be used if the statement is invalid, but they will return failure or some
+  // default value. This is because the statement can become invalid in the
+  // middle of executing a command if there is a serioud error and the database
+  // has to be reset.
+  bool is_valid() const { return ref_->is_valid(); }
+
+  // These operators allow conveniently checking if the statement is valid
+  // or not. See the pattern above for an example.
+  operator bool() const { return is_valid(); }
+  bool operator!() const { return !is_valid(); }
+
+  // Running -------------------------------------------------------------------
+
+  // Executes the statement, returning true on success. This is like Step but
+  // for when there is no output, like an INSERT statement.
+  bool Run();
+
+  // Executes the statement, returning true if there is a row of data returned.
+  // You can keep calling Step() until it returns false to iterate through all
+  // the rows in your result set.
+  //
+  // When Step returns false, the result is either that there is no more data
+  // or there is an error. This makes it most convenient for loop usage. If you
+  // need to disambiguate these cases, use Succeeded().
+  //
+  // Typical example:
+  //   while (s.Step()) {
+  //     ...
+  //   }
+  //   return s.Succeeded();
+  bool Step();
+
+  // Resets the statement to its initial condition. This includes clearing all
+  // the bound variables and any current result row.
+  void Reset();
+
+  // Returns true if the last executed thing in this statement succeeded. If
+  // there was no last executed thing or the statement is invalid, this will
+  // return false.
+  bool Succeeded() const;
+
+  // Binding -------------------------------------------------------------------
+
+  // These all take a 0-based argument index and return true on failure. You
+  // may not always care about the return value (they'll DCHECK if they fail).
+  // The main thing you may want to check is when binding large blobs or
+  // strings there may be out of memory.
+  bool BindNull(int col);
+  bool BindBool(int col, bool val);
+  bool BindInt(int col, int val);
+  bool BindInt64(int col, int64 val);
+  bool BindDouble(int col, double val);
+  bool BindCString(int col, const char* val);
+  bool BindString(int col, const std::string& val);
+  bool BindString16(int col, const string16& value);
+  bool BindBlob(int col, const void* value, int value_len);
+
+  // Retrieving ----------------------------------------------------------------
+
+  // Returns the number of output columns in the result.
+  int ColumnCount() const;
+
+  // Returns the type associated with the given column.
+  //
+  // Watch out: the type may be undefined if you've done something to cause a
+  // "type conversion." This means requesting the value of a column of a type
+  // where that type is not the native type. For safety, call ColumnType only
+  // on a column before getting the value out in any way.
+  ColType ColumnType(int col) const;
+
+  // These all take a 0-based argument index.
+  bool ColumnBool(int col) const;
+  int ColumnInt(int col) const;
+  int64 ColumnInt64(int col) const;
+  double ColumnDouble(int col) const;
+  std::string ColumnString(int col) const;
+  string16 ColumnString16(int col) const;
+
+  // When reading a blob, you can get a raw pointer to the underlying data,
+  // along with the length, or you can just ask us to copy the blob into a
+  // vector. Danger! ColumnBlob may return NULL if there is no data!
+  int ColumnByteLength(int col) const;
+  const void* ColumnBlob(int col) const;
+  bool ColumnBlobAsString(int col, std::string* blob);
+  void ColumnBlobAsVector(int col, std::vector<char>* val) const;
+  void ColumnBlobAsVector(int col, std::vector<unsigned char>* val) const;
+
+  // Diagnostics --------------------------------------------------------------
+
+  // Returns the original text of sql statement. Do not keep a pointer to it.
+  const char* GetSQLStatement();
+
+ private:
+  // This is intended to check for serious errors and report them to the
+  // connection object. It takes a sqlite error code, and returns the same
+  // code. Currently this function just updates the succeeded flag, but will be
+  // enhanced in the future to do the notification.
+  int CheckError(int err);
+
+  // The actual sqlite statement. This may be unique to us, or it may be cached
+  // by the connection, which is why it's refcounted. This pointer is
+  // guaranteed non-NULL.
+  scoped_refptr<Connection::StatementRef> ref_;
+
+  // See Succeeded() for what this holds.
+  bool succeeded_;
+
+  DISALLOW_COPY_AND_ASSIGN(Statement);
+};
+
+}  // namespace sql
+
+#endif  // SQL_STATEMENT_H_
diff --git a/sql/statement_unittest.cc b/sql/statement_unittest.cc
new file mode 100644
index 0000000..1d10fe0
--- /dev/null
+++ b/sql/statement_unittest.cc
@@ -0,0 +1,126 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <string>
+
+#include "base/file_util.h"
+#include "base/scoped_temp_dir.h"
+#include "sql/connection.h"
+#include "sql/statement.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "third_party/sqlite/sqlite3.h"
+
+class StatementErrorHandler : public sql::ErrorDelegate {
+ public:
+  StatementErrorHandler() : error_(SQLITE_OK) {}
+
+  virtual int OnError(int error, sql::Connection* connection,
+                      sql::Statement* stmt) {
+    error_ = error;
+    const char* sql_txt = stmt ? stmt->GetSQLStatement() : NULL;
+    sql_text_ = sql_txt ? sql_txt : "no statement available";
+    return error;
+  }
+
+  int error() const { return error_; }
+
+  void reset_error() {
+    sql_text_.clear();
+    error_ = SQLITE_OK;
+  }
+
+  const char* sql_statement() const { return sql_text_.c_str(); }
+
+ private:
+  int error_;
+  std::string sql_text_;
+};
+
+class SQLStatementTest : public testing::Test {
+ public:
+  SQLStatementTest() : error_handler_(new StatementErrorHandler) {}
+
+  void SetUp() {
+    ASSERT_TRUE(temp_dir_.CreateUniqueTempDir());
+    ASSERT_TRUE(db_.Open(temp_dir_.path().AppendASCII("SQLStatementTest.db")));
+
+    // The |error_handler_| will be called if any sqlite statement operation
+    // returns an error code.
+    db_.set_error_delegate(error_handler_);
+  }
+
+  void TearDown() {
+    // If any error happened the original sql statement can be found in
+    // error_handler_->sql_statement().
+    EXPECT_EQ(SQLITE_OK, error_handler_->error());
+    db_.Close();
+  }
+
+  sql::Connection& db() { return db_; }
+
+  int sqlite_error() const { return error_handler_->error(); }
+  void reset_error() const { error_handler_->reset_error(); }
+
+ private:
+  ScopedTempDir temp_dir_;
+  sql::Connection db_;
+  scoped_refptr<StatementErrorHandler> error_handler_;
+};
+
+TEST_F(SQLStatementTest, Assign) {
+  sql::Statement s;
+  EXPECT_FALSE(s);  // bool conversion operator.
+  EXPECT_TRUE(!s);  // ! operator.
+  EXPECT_FALSE(s.is_valid());
+
+  s.Assign(db().GetUniqueStatement("CREATE TABLE foo (a, b)"));
+  EXPECT_TRUE(s);
+  EXPECT_FALSE(!s);
+  EXPECT_TRUE(s.is_valid());
+}
+
+TEST_F(SQLStatementTest, Run) {
+  ASSERT_TRUE(db().Execute("CREATE TABLE foo (a, b)"));
+  ASSERT_TRUE(db().Execute("INSERT INTO foo (a, b) VALUES (3, 12)"));
+
+  sql::Statement s(db().GetUniqueStatement("SELECT b FROM foo WHERE a=?"));
+  EXPECT_FALSE(s.Succeeded());
+
+  // Stepping it won't work since we haven't bound the value.
+  EXPECT_FALSE(s.Step());
+
+  // Run should fail since this produces output, and we should use Step(). This
+  // gets a bit wonky since sqlite says this is OK so succeeded is set.
+  s.Reset();
+  s.BindInt(0, 3);
+  EXPECT_FALSE(s.Run());
+  EXPECT_EQ(SQLITE_ROW, db().GetErrorCode());
+  EXPECT_TRUE(s.Succeeded());
+
+  // Resetting it should put it back to the previous state (not runnable).
+  s.Reset();
+  EXPECT_FALSE(s.Succeeded());
+
+  // Binding and stepping should produce one row.
+  s.BindInt(0, 3);
+  EXPECT_TRUE(s.Step());
+  EXPECT_TRUE(s.Succeeded());
+  EXPECT_EQ(12, s.ColumnInt(0));
+  EXPECT_FALSE(s.Step());
+  EXPECT_TRUE(s.Succeeded());
+}
+
+TEST_F(SQLStatementTest, BasicErrorCallback) {
+  ASSERT_TRUE(db().Execute("CREATE TABLE foo (a INTEGER PRIMARY KEY, b)"));
+  EXPECT_EQ(SQLITE_OK, sqlite_error());
+  // Insert in the foo table the primary key. It is an error to insert
+  // something other than an number. This error causes the error callback
+  // handler to be called with SQLITE_MISMATCH as error code.
+  sql::Statement s(db().GetUniqueStatement("INSERT INTO foo (a) VALUES (?)"));
+  EXPECT_TRUE(s.is_valid());
+  s.BindCString(0, "bad bad");
+  EXPECT_FALSE(s.Run());
+  EXPECT_EQ(SQLITE_MISMATCH, sqlite_error());
+  reset_error();
+}
diff --git a/sql/transaction.cc b/sql/transaction.cc
new file mode 100644
index 0000000..06bcbeb
--- /dev/null
+++ b/sql/transaction.cc
@@ -0,0 +1,51 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "sql/transaction.h"
+
+#include "base/logging.h"
+#include "sql/connection.h"
+
+namespace sql {
+
+Transaction::Transaction(Connection* connection)
+    : connection_(connection),
+      is_open_(false) {
+}
+
+Transaction::~Transaction() {
+  if (is_open_)
+    connection_->RollbackTransaction();
+}
+
+bool Transaction::Begin() {
+  if (is_open_) {
+    NOTREACHED() << "Beginning a transaction twice!";
+    return false;
+  }
+  is_open_ = connection_->BeginTransaction();
+  return is_open_;
+}
+
+void Transaction::Rollback() {
+  if (!is_open_) {
+    NOTREACHED() << "Attempting to roll back a nonexistent transaction. "
+                 << "Did you remember to call Begin() and check its return?";
+    return;
+  }
+  is_open_ = false;
+  connection_->RollbackTransaction();
+}
+
+bool Transaction::Commit() {
+  if (!is_open_) {
+    NOTREACHED() << "Attempting to commit a nonexistent transaction. "
+                 << "Did you remember to call Begin() and check its return?";
+    return false;
+  }
+  is_open_ = false;
+  return connection_->CommitTransaction();
+}
+
+}  // namespace sql
diff --git a/sql/transaction.h b/sql/transaction.h
new file mode 100644
index 0000000..5e1a418
--- /dev/null
+++ b/sql/transaction.h
@@ -0,0 +1,57 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef SQL_TRANSACTION_H_
+#define SQL_TRANSACTION_H_
+#pragma once
+
+#include "base/basictypes.h"
+
+namespace sql {
+
+class Connection;
+
+class Transaction {
+ public:
+  // Creates the scoped transaction object. You MUST call Begin() to begin the
+  // transaction. If you have begun a transaction and not committed it, the
+  // constructor will roll back the transaction. If you want to commit, you
+  // need to manually call Commit before this goes out of scope.
+  explicit Transaction(Connection* connection);
+  ~Transaction();
+
+  // Returns true when there is a transaction that has been successfully begun.
+  bool is_open() const { return is_open_; }
+
+  // Begins the transaction. This uses the default sqlite "deferred" transaction
+  // type, which means that the DB lock is lazily acquired the next time the
+  // database is accessed, not in the begin transaction command.
+  //
+  // Returns false on failure. Note that if this fails, you shouldn't do
+  // anything you expect to be actually transactional, because it won't be!
+  bool Begin();
+
+  // Rolls back the transaction. This will happen automatically if you do
+  // nothing when the transaction goes out of scope.
+  void Rollback();
+
+  // Commits the transaction, returning true on success. This will return
+  // false if sqlite could not commit it, or if another transaction in the
+  // same outermost transaction has been rolled back (which necessitates a
+  // rollback of all transactions in that outermost one).
+  bool Commit();
+
+ private:
+  Connection* connection_;
+
+  // True when the transaction is open, false when it's already been committed
+  // or rolled back.
+  bool is_open_;
+
+  DISALLOW_COPY_AND_ASSIGN(Transaction);
+};
+
+}  // namespace sql
+
+#endif  // SQL_TRANSACTION_H_
diff --git a/sql/transaction_unittest.cc b/sql/transaction_unittest.cc
new file mode 100644
index 0000000..f306a5c
--- /dev/null
+++ b/sql/transaction_unittest.cc
@@ -0,0 +1,133 @@
+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "base/file_util.h"
+#include "base/scoped_temp_dir.h"
+#include "sql/connection.h"
+#include "sql/statement.h"
+#include "sql/transaction.h"
+#include "testing/gtest/include/gtest/gtest.h"
+#include "third_party/sqlite/sqlite3.h"
+
+class SQLTransactionTest : public testing::Test {
+ public:
+  SQLTransactionTest() {}
+
+  void SetUp() {
+    ASSERT_TRUE(temp_dir_.CreateUniqueTempDir());
+    ASSERT_TRUE(db_.Open(
+        temp_dir_.path().AppendASCII("SQLTransactionTest.db")));
+
+    ASSERT_TRUE(db().Execute("CREATE TABLE foo (a, b)"));
+  }
+
+  void TearDown() {
+    db_.Close();
+  }
+
+  sql::Connection& db() { return db_; }
+
+  // Returns the number of rows in table "foo".
+  int CountFoo() {
+    sql::Statement count(db().GetUniqueStatement("SELECT count(*) FROM foo"));
+    count.Step();
+    return count.ColumnInt(0);
+  }
+
+ private:
+  ScopedTempDir temp_dir_;
+  sql::Connection db_;
+};
+
+TEST_F(SQLTransactionTest, Commit) {
+  {
+    sql::Transaction t(&db());
+    EXPECT_FALSE(t.is_open());
+    EXPECT_TRUE(t.Begin());
+    EXPECT_TRUE(t.is_open());
+
+    EXPECT_TRUE(db().Execute("INSERT INTO foo (a, b) VALUES (1, 2)"));
+
+    t.Commit();
+    EXPECT_FALSE(t.is_open());
+  }
+
+  EXPECT_EQ(1, CountFoo());
+}
+
+TEST_F(SQLTransactionTest, Rollback) {
+  // Test some basic initialization, and that rollback runs when you exit the
+  // scope.
+  {
+    sql::Transaction t(&db());
+    EXPECT_FALSE(t.is_open());
+    EXPECT_TRUE(t.Begin());
+    EXPECT_TRUE(t.is_open());
+
+    EXPECT_TRUE(db().Execute("INSERT INTO foo (a, b) VALUES (1, 2)"));
+  }
+
+  // Nothing should have been committed since it was implicitly rolled back.
+  EXPECT_EQ(0, CountFoo());
+
+  // Test explicit rollback.
+  sql::Transaction t2(&db());
+  EXPECT_FALSE(t2.is_open());
+  EXPECT_TRUE(t2.Begin());
+
+  EXPECT_TRUE(db().Execute("INSERT INTO foo (a, b) VALUES (1, 2)"));
+  t2.Rollback();
+  EXPECT_FALSE(t2.is_open());
+
+  // Nothing should have been committed since it was explicitly rolled back.
+  EXPECT_EQ(0, CountFoo());
+}
+
+// Rolling back any part of a transaction should roll back all of them.
+TEST_F(SQLTransactionTest, NestedRollback) {
+  EXPECT_EQ(0, db().transaction_nesting());
+
+  // Outermost transaction.
+  {
+    sql::Transaction outer(&db());
+    EXPECT_TRUE(outer.Begin());
+    EXPECT_EQ(1, db().transaction_nesting());
+
+    // The first inner one gets committed.
+    {
+      sql::Transaction inner1(&db());
+      EXPECT_TRUE(inner1.Begin());
+      EXPECT_TRUE(db().Execute("INSERT INTO foo (a, b) VALUES (1, 2)"));
+      EXPECT_EQ(2, db().transaction_nesting());
+
+      inner1.Commit();
+      EXPECT_EQ(1, db().transaction_nesting());
+    }
+
+    // One row should have gotten inserted.
+    EXPECT_EQ(1, CountFoo());
+
+    // The second inner one gets rolled back.
+    {
+      sql::Transaction inner2(&db());
+      EXPECT_TRUE(inner2.Begin());
+      EXPECT_TRUE(db().Execute("INSERT INTO foo (a, b) VALUES (1, 2)"));
+      EXPECT_EQ(2, db().transaction_nesting());
+
+      inner2.Rollback();
+      EXPECT_EQ(1, db().transaction_nesting());
+    }
+
+    // A third inner one will fail in Begin since one has already been rolled
+    // back.
+    EXPECT_EQ(1, db().transaction_nesting());
+    {
+      sql::Transaction inner3(&db());
+      EXPECT_FALSE(inner3.Begin());
+      EXPECT_EQ(1, db().transaction_nesting());
+    }
+  }
+  EXPECT_EQ(0, db().transaction_nesting());
+  EXPECT_EQ(0, CountFoo());
+}