sql/connection.cc

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This source file includes following definitions.
SetTimeout
BackupDatabase
ValidAttachmentPoint
InitializeSqlite
GetSqlite3File
ShouldIgnoreSqliteError
SetErrorIgnorer
ResetErrorIgnorer
was_valid_
Close
poisoned_
Open
OpenInMemory
OpenTemporary
CloseInternal
Close
Preload
TrimMemory
Raze
RazeWithTimout
RazeAndClose
Poison
Delete
BeginTransaction
RollbackTransaction
CommitTransaction
RollbackAllTransactions
AttachDatabase
DetachDatabase
ExecuteAndReturnErrorCode
Execute
ExecuteWithTimeout
HasCachedStatement
GetCachedStatement
GetUniqueStatement
GetUntrackedStatement
GetSchema
IsSQLValid
DoesTableExist
DoesIndexExist
DoesTableOrIndexExist
DoesColumnExist
GetLastInsertRowId
GetLastChangeCount
GetErrorCode
GetLastErrno
GetErrorMessage
OpenInternal
DoRollback
StatementRefCreated
StatementRefDeleted
AddTaggedHistogram
OnSqliteError
FullIntegrityCheck
QuickIntegrityCheck
IntegrityCheckHelper
// Copyright (c) 2012 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/files/file_path.h"
#include "base/file_util.h"
#include "base/lazy_instance.h"
#include "base/logging.h"
#include "base/metrics/histogram.h"
#include "base/metrics/sparse_histogram.h"
#include "base/strings/string_split.h"
#include "base/strings/string_util.h"
#include "base/strings/stringprintf.h"
#include "base/strings/utf_string_conversions.h"
#include "base/synchronization/lock.h"
#include "sql/statement.h"
#include "third_party/sqlite/sqlite3.h"

#if defined(OS_IOS) && defined(USE_SYSTEM_SQLITE)
#include "third_party/sqlite/src/ext/icu/sqliteicu.h"
#endif

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 int kBusyTimeoutSeconds = 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_;
};

// Helper to "safely" enable writable_schema.  No error checking
// because it is reasonable to just forge ahead in case of an error.
// If turning it on fails, then most likely nothing will work, whereas
// if turning it off fails, it only matters if some code attempts to
// continue working with the database and tries to modify the
// sqlite_master table (none of our code does this).
class ScopedWritableSchema {
 public:
  explicit ScopedWritableSchema(sqlite3* db)
      : db_(db) {
    sqlite3_exec(db_, "PRAGMA writable_schema=1", NULL, NULL, NULL);
  }
  ~ScopedWritableSchema() {
    sqlite3_exec(db_, "PRAGMA writable_schema=0", NULL, NULL, NULL);
  }

 private:
  sqlite3* db_;
};

// Helper to wrap the sqlite3_backup_*() step of Raze().  Return
// SQLite error code from running the backup step.
int BackupDatabase(sqlite3* src, sqlite3* dst, const char* db_name) {
  DCHECK_NE(src, dst);
  sqlite3_backup* backup = sqlite3_backup_init(dst, db_name, src, db_name);
  if (!backup) {
    // Since this call only sets things up, this indicates a gross
    // error in SQLite.
    DLOG(FATAL) << "Unable to start sqlite3_backup(): " << sqlite3_errmsg(dst);
    return sqlite3_errcode(dst);
  }

  // -1 backs up the entire database.
  int rc = sqlite3_backup_step(backup, -1);
  int pages = sqlite3_backup_pagecount(backup);
  sqlite3_backup_finish(backup);

  // If successful, exactly one page should have been backed up.  If
  // this breaks, check this function to make sure assumptions aren't
  // being broken.
  if (rc == SQLITE_DONE)
    DCHECK_EQ(pages, 1);

  return rc;
}

// Be very strict on attachment point.  SQLite can handle a much wider
// character set with appropriate quoting, but Chromium code should
// just use clean names to start with.
bool ValidAttachmentPoint(const char* attachment_point) {
  for (size_t i = 0; attachment_point[i]; ++i) {
    if (!((attachment_point[i] >= '0' && attachment_point[i] <= '9') ||
          (attachment_point[i] >= 'a' && attachment_point[i] <= 'z') ||
          (attachment_point[i] >= 'A' && attachment_point[i] <= 'Z') ||
          attachment_point[i] == '_')) {
      return false;
    }
  }
  return true;
}

// SQLite automatically calls sqlite3_initialize() lazily, but
// sqlite3_initialize() uses double-checked locking and thus can have
// data races.
//
// TODO(shess): Another alternative would be to have
// sqlite3_initialize() called as part of process bring-up.  If this
// is changed, remove the dynamic_annotations dependency in sql.gyp.
base::LazyInstance<base::Lock>::Leaky
    g_sqlite_init_lock = LAZY_INSTANCE_INITIALIZER;
void InitializeSqlite() {
  base::AutoLock lock(g_sqlite_init_lock.Get());
  sqlite3_initialize();
}

// Helper to get the sqlite3_file* associated with the "main" database.
int GetSqlite3File(sqlite3* db, sqlite3_file** file) {
  *file = NULL;
  int rc = sqlite3_file_control(db, NULL, SQLITE_FCNTL_FILE_POINTER, file);
  if (rc != SQLITE_OK)
    return rc;

  // TODO(shess): NULL in file->pMethods has been observed on android_dbg
  // content_unittests, even though it should not be possible.
  // http://crbug.com/329982
  if (!*file || !(*file)->pMethods)
    return SQLITE_ERROR;

  return rc;
}

}  // namespace

namespace sql {

// static
Connection::ErrorIgnorerCallback* Connection::current_ignorer_cb_ = NULL;

// static
bool Connection::ShouldIgnoreSqliteError(int error) {
  if (!current_ignorer_cb_)
    return false;
  return current_ignorer_cb_->Run(error);
}

// static
void Connection::SetErrorIgnorer(Connection::ErrorIgnorerCallback* cb) {
  CHECK(current_ignorer_cb_ == NULL);
  current_ignorer_cb_ = cb;
}

// static
void Connection::ResetErrorIgnorer() {
  CHECK(current_ignorer_cb_);
  current_ignorer_cb_ = NULL;
}

bool StatementID::operator<(const StatementID& other) const {
  if (number_ != other.number_)
    return number_ < other.number_;
  return strcmp(str_, other.str_) < 0;
}

Connection::StatementRef::StatementRef(Connection* connection,
                                       sqlite3_stmt* stmt,
                                       bool was_valid)
    : connection_(connection),
      stmt_(stmt),
      was_valid_(was_valid) {
  if (connection)
    connection_->StatementRefCreated(this);
}

Connection::StatementRef::~StatementRef() {
  if (connection_)
    connection_->StatementRefDeleted(this);
  Close(false);
}

void Connection::StatementRef::Close(bool forced) {
  if (stmt_) {
    // Call to AssertIOAllowed() cannot go at the beginning of the function
    // because Close() is called unconditionally from destructor to clean
    // connection_. And if this is inactive statement this won't cause any
    // disk access and destructor most probably will be called on thread
    // not allowing disk access.
    // TODO(paivanof@gmail.com): This should move to the beginning
    // of the function. http://crbug.com/136655.
    AssertIOAllowed();
    sqlite3_finalize(stmt_);
    stmt_ = NULL;
  }
  connection_ = NULL;  // The connection may be getting deleted.

  // Forced close is expected to happen from a statement error
  // handler.  In that case maintain the sense of |was_valid_| which
  // previously held for this ref.
  was_valid_ = was_valid_ && forced;
}

Connection::Connection()
    : db_(NULL),
      page_size_(0),
      cache_size_(0),
      exclusive_locking_(false),
      restrict_to_user_(false),
      transaction_nesting_(0),
      needs_rollback_(false),
      in_memory_(false),
      poisoned_(false) {
}

Connection::~Connection() {
  Close();
}

bool Connection::Open(const base::FilePath& path) {
  if (!histogram_tag_.empty()) {
    int64 size_64 = 0;
    if (base::GetFileSize(path, &size_64)) {
      size_t sample = static_cast<size_t>(size_64 / 1024);
      std::string full_histogram_name = "Sqlite.SizeKB." + histogram_tag_;
      base::HistogramBase* histogram =
          base::Histogram::FactoryGet(
              full_histogram_name, 1, 1000000, 50,
              base::HistogramBase::kUmaTargetedHistogramFlag);
      if (histogram)
        histogram->Add(sample);
    }
  }

#if defined(OS_WIN)
  return OpenInternal(base::WideToUTF8(path.value()), RETRY_ON_POISON);
#elif defined(OS_POSIX)
  return OpenInternal(path.value(), RETRY_ON_POISON);
#endif
}

bool Connection::OpenInMemory() {
  in_memory_ = true;
  return OpenInternal(":memory:", NO_RETRY);
}

bool Connection::OpenTemporary() {
  return OpenInternal("", NO_RETRY);
}

void Connection::CloseInternal(bool forced) {
  // TODO(shess): Calling "PRAGMA journal_mode = DELETE" at this point
  // will delete the -journal file.  For ChromiumOS or other more
  // embedded systems, this is probably not appropriate, whereas on
  // desktop it might make some sense.

  // sqlite3_close() needs all prepared statements to be finalized.

  // Release cached statements.
  statement_cache_.clear();

  // With cached statements released, in-use statements will remain.
  // Closing the database while statements are in use is an API
  // violation, except for forced close (which happens from within a
  // statement's error handler).
  DCHECK(forced || open_statements_.empty());

  // Deactivate any outstanding statements so sqlite3_close() works.
  for (StatementRefSet::iterator i = open_statements_.begin();
       i != open_statements_.end(); ++i)
    (*i)->Close(forced);
  open_statements_.clear();

  if (db_) {
    // Call to AssertIOAllowed() cannot go at the beginning of the function
    // because Close() must be called from destructor to clean
    // statement_cache_, it won't cause any disk access and it most probably
    // will happen on thread not allowing disk access.
    // TODO(paivanof@gmail.com): This should move to the beginning
    // of the function. http://crbug.com/136655.
    AssertIOAllowed();

    int rc = sqlite3_close(db_);
    if (rc != SQLITE_OK) {
      UMA_HISTOGRAM_SPARSE_SLOWLY("Sqlite.CloseFailure", rc);
      DLOG(FATAL) << "sqlite3_close failed: " << GetErrorMessage();
    }
  }
  db_ = NULL;
}

void Connection::Close() {
  // If the database was already closed by RazeAndClose(), then no
  // need to close again.  Clear the |poisoned_| bit so that incorrect
  // API calls are caught.
  if (poisoned_) {
    poisoned_ = false;
    return;
  }

  CloseInternal(false);
}

void Connection::Preload() {
  AssertIOAllowed();

  if (!db_) {
    DLOG_IF(FATAL, !poisoned_) << "Cannot preload null db";
    return;
  }

  // Use local settings if provided, otherwise use documented defaults.  The
  // actual results could be fetching via PRAGMA calls.
  const int page_size = page_size_ ? page_size_ : 1024;
  sqlite3_int64 preload_size = page_size * (cache_size_ ? cache_size_ : 2000);
  if (preload_size < 1)
    return;

  sqlite3_file* file = NULL;
  int rc = GetSqlite3File(db_, &file);
  if (rc != SQLITE_OK)
    return;

  sqlite3_int64 file_size = 0;
  rc = file->pMethods->xFileSize(file, &file_size);
  if (rc != SQLITE_OK)
    return;

  // Don't preload more than the file contains.
  if (preload_size > file_size)
    preload_size = file_size;

  scoped_ptr<char[]> buf(new char[page_size]);
  for (sqlite3_int64 pos = 0; pos < file_size; pos += page_size) {
    rc = file->pMethods->xRead(file, buf.get(), page_size, pos);
    if (rc != SQLITE_OK)
      return;
  }
}

void Connection::TrimMemory(bool aggressively) {
  if (!db_)
    return;

  // TODO(shess): investigate using sqlite3_db_release_memory() when possible.
  int original_cache_size;
  {
    Statement sql_get_original(GetUniqueStatement("PRAGMA cache_size"));
    if (!sql_get_original.Step()) {
      DLOG(WARNING) << "Could not get cache size " << GetErrorMessage();
      return;
    }
    original_cache_size = sql_get_original.ColumnInt(0);
  }
  int shrink_cache_size = aggressively ? 1 : (original_cache_size / 2);

  // Force sqlite to try to reduce page cache usage.
  const std::string sql_shrink =
      base::StringPrintf("PRAGMA cache_size=%d", shrink_cache_size);
  if (!Execute(sql_shrink.c_str()))
    DLOG(WARNING) << "Could not shrink cache size: " << GetErrorMessage();

  // Restore cache size.
  const std::string sql_restore =
      base::StringPrintf("PRAGMA cache_size=%d", original_cache_size);
  if (!Execute(sql_restore.c_str()))
    DLOG(WARNING) << "Could not restore cache size: " << GetErrorMessage();
}

// Create an in-memory database with the existing database's page
// size, then backup that database over the existing database.
bool Connection::Raze() {
  AssertIOAllowed();

  if (!db_) {
    DLOG_IF(FATAL, !poisoned_) << "Cannot raze null db";
    return false;
  }

  if (transaction_nesting_ > 0) {
    DLOG(FATAL) << "Cannot raze within a transaction";
    return false;
  }

  sql::Connection null_db;
  if (!null_db.OpenInMemory()) {
    DLOG(FATAL) << "Unable to open in-memory database.";
    return false;
  }

  if (page_size_) {
    // Enforce SQLite restrictions on |page_size_|.
    DCHECK(!(page_size_ & (page_size_ - 1)))
        << " page_size_ " << page_size_ << " is not a power of two.";
    const int kSqliteMaxPageSize = 32768;  // from sqliteLimit.h
    DCHECK_LE(page_size_, kSqliteMaxPageSize);
    const std::string sql =
        base::StringPrintf("PRAGMA page_size=%d", page_size_);
    if (!null_db.Execute(sql.c_str()))
      return false;
  }

#if defined(OS_ANDROID)
  // Android compiles with SQLITE_DEFAULT_AUTOVACUUM.  Unfortunately,
  // in-memory databases do not respect this define.
  // TODO(shess): Figure out a way to set this without using platform
  // specific code.  AFAICT from sqlite3.c, the only way to do it
  // would be to create an actual filesystem database, which is
  // unfortunate.
  if (!null_db.Execute("PRAGMA auto_vacuum = 1"))
    return false;
#endif

  // The page size doesn't take effect until a database has pages, and
  // at this point the null database has none.  Changing the schema
  // version will create the first page.  This will not affect the
  // schema version in the resulting database, as SQLite's backup
  // implementation propagates the schema version from the original
  // connection to the new version of the database, incremented by one
  // so that other readers see the schema change and act accordingly.
  if (!null_db.Execute("PRAGMA schema_version = 1"))
    return false;

  // SQLite tracks the expected number of database pages in the first
  // page, and if it does not match the total retrieved from a
  // filesystem call, treats the database as corrupt.  This situation
  // breaks almost all SQLite calls.  "PRAGMA writable_schema" can be
  // used to hint to SQLite to soldier on in that case, specifically
  // for purposes of recovery.  [See SQLITE_CORRUPT_BKPT case in
  // sqlite3.c lockBtree().]
  // TODO(shess): With this, "PRAGMA auto_vacuum" and "PRAGMA
  // page_size" can be used to query such a database.
  ScopedWritableSchema writable_schema(db_);

  const char* kMain = "main";
  int rc = BackupDatabase(null_db.db_, db_, kMain);
  UMA_HISTOGRAM_SPARSE_SLOWLY("Sqlite.RazeDatabase",rc);

  // The destination database was locked.
  if (rc == SQLITE_BUSY) {
    return false;
  }

  // SQLITE_NOTADB can happen if page 1 of db_ exists, but is not
  // formatted correctly.  SQLITE_IOERR_SHORT_READ can happen if db_
  // isn't even big enough for one page.  Either way, reach in and
  // truncate it before trying again.
  // TODO(shess): Maybe it would be worthwhile to just truncate from
  // the get-go?
  if (rc == SQLITE_NOTADB || rc == SQLITE_IOERR_SHORT_READ) {
    sqlite3_file* file = NULL;
    rc = GetSqlite3File(db_, &file);
    if (rc != SQLITE_OK) {
      DLOG(FATAL) << "Failure getting file handle.";
      return false;
    }

    rc = file->pMethods->xTruncate(file, 0);
    if (rc != SQLITE_OK) {
      UMA_HISTOGRAM_SPARSE_SLOWLY("Sqlite.RazeDatabaseTruncate",rc);
      DLOG(FATAL) << "Failed to truncate file.";
      return false;
    }

    rc = BackupDatabase(null_db.db_, db_, kMain);
    UMA_HISTOGRAM_SPARSE_SLOWLY("Sqlite.RazeDatabase2",rc);

    if (rc != SQLITE_DONE) {
      DLOG(FATAL) << "Failed retrying Raze().";
    }
  }

  // The entire database should have been backed up.
  if (rc != SQLITE_DONE) {
    // TODO(shess): Figure out which other cases can happen.
    DLOG(FATAL) << "Unable to copy entire null database.";
    return false;
  }

  return true;
}

bool Connection::RazeWithTimout(base::TimeDelta timeout) {
  if (!db_) {
    DLOG_IF(FATAL, !poisoned_) << "Cannot raze null db";
    return false;
  }

  ScopedBusyTimeout busy_timeout(db_);
  busy_timeout.SetTimeout(timeout);
  return Raze();
}

bool Connection::RazeAndClose() {
  if (!db_) {
    DLOG_IF(FATAL, !poisoned_) << "Cannot raze null db";
    return false;
  }

  // Raze() cannot run in a transaction.
  RollbackAllTransactions();

  bool result = Raze();

  CloseInternal(true);

  // Mark the database so that future API calls fail appropriately,
  // but don't DCHECK (because after calling this function they are
  // expected to fail).
  poisoned_ = true;

  return result;
}

void Connection::Poison() {
  if (!db_) {
    DLOG_IF(FATAL, !poisoned_) << "Cannot poison null db";
    return;
  }

  RollbackAllTransactions();
  CloseInternal(true);

  // Mark the database so that future API calls fail appropriately,
  // but don't DCHECK (because after calling this function they are
  // expected to fail).
  poisoned_ = true;
}

// TODO(shess): To the extent possible, figure out the optimal
// ordering for these deletes which will prevent other connections
// from seeing odd behavior.  For instance, it may be necessary to
// manually lock the main database file in a SQLite-compatible fashion
// (to prevent other processes from opening it), then delete the
// journal files, then delete the main database file.  Another option
// might be to lock the main database file and poison the header with
// junk to prevent other processes from opening it successfully (like
// Gears "SQLite poison 3" trick).
//
// static
bool Connection::Delete(const base::FilePath& path) {
  base::ThreadRestrictions::AssertIOAllowed();

  base::FilePath journal_path(path.value() + FILE_PATH_LITERAL("-journal"));
  base::FilePath wal_path(path.value() + FILE_PATH_LITERAL("-wal"));

  base::DeleteFile(journal_path, false);
  base::DeleteFile(wal_path, false);
  base::DeleteFile(path, false);

  return !base::PathExists(journal_path) &&
      !base::PathExists(wal_path) &&
      !base::PathExists(path);
}

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.Run())
      return false;
  }
  transaction_nesting_++;
  return success;
}

void Connection::RollbackTransaction() {
  if (!transaction_nesting_) {
    DLOG_IF(FATAL, !poisoned_) << "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_) {
    DLOG_IF(FATAL, !poisoned_) << "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"));
  return commit.Run();
}

void Connection::RollbackAllTransactions() {
  if (transaction_nesting_ > 0) {
    transaction_nesting_ = 0;
    DoRollback();
  }
}

bool Connection::AttachDatabase(const base::FilePath& other_db_path,
                                const char* attachment_point) {
  DCHECK(ValidAttachmentPoint(attachment_point));

  Statement s(GetUniqueStatement("ATTACH DATABASE ? AS ?"));
#if OS_WIN
  s.BindString16(0, other_db_path.value());
#else
  s.BindString(0, other_db_path.value());
#endif
  s.BindString(1, attachment_point);
  return s.Run();
}

bool Connection::DetachDatabase(const char* attachment_point) {
  DCHECK(ValidAttachmentPoint(attachment_point));

  Statement s(GetUniqueStatement("DETACH DATABASE ?"));
  s.BindString(0, attachment_point);
  return s.Run();
}

int Connection::ExecuteAndReturnErrorCode(const char* sql) {
  AssertIOAllowed();
  if (!db_) {
    DLOG_IF(FATAL, !poisoned_) << "Illegal use of connection without a db";
    return SQLITE_ERROR;
  }
  return sqlite3_exec(db_, sql, NULL, NULL, NULL);
}

bool Connection::Execute(const char* sql) {
  if (!db_) {
    DLOG_IF(FATAL, !poisoned_) << "Illegal use of connection without a db";
    return false;
  }

  int error = ExecuteAndReturnErrorCode(sql);
  if (error != SQLITE_OK)
    error = OnSqliteError(error, NULL, sql);

  // This needs to be a FATAL log because the error case of arriving here is
  // that there's a malformed SQL statement. This can arise in development if
  // a change alters the schema but not all queries adjust.  This can happen
  // in production if the schema is corrupted.
  if (error == SQLITE_ERROR)
    DLOG(FATAL) << "SQL Error in " << sql << ", " << GetErrorMessage();
  return error == SQLITE_OK;
}

bool Connection::ExecuteWithTimeout(const char* sql, base::TimeDelta timeout) {
  if (!db_) {
    DLOG_IF(FATAL, !poisoned_) << "Illegal use of connection without a db";
    return false;
  }

  ScopedBusyTimeout busy_timeout(db_);
  busy_timeout.SetTimeout(timeout);
  return Execute(sql);
}

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) {
  AssertIOAllowed();

  // Return inactive statement.
  if (!db_)
    return new StatementRef(NULL, NULL, poisoned_);

  sqlite3_stmt* stmt = NULL;
  int rc = sqlite3_prepare_v2(db_, sql, -1, &stmt, NULL);
  if (rc != SQLITE_OK) {
    // This is evidence of a syntax error in the incoming SQL.
    DLOG(FATAL) << "SQL compile error " << GetErrorMessage();

    // It could also be database corruption.
    OnSqliteError(rc, NULL, sql);
    return new StatementRef(NULL, NULL, false);
  }
  return new StatementRef(this, stmt, true);
}

scoped_refptr<Connection::StatementRef> Connection::GetUntrackedStatement(
    const char* sql) const {
  // Return inactive statement.
  if (!db_)
    return new StatementRef(NULL, NULL, poisoned_);

  sqlite3_stmt* stmt = NULL;
  int rc = sqlite3_prepare_v2(db_, sql, -1, &stmt, NULL);
  if (rc != SQLITE_OK) {
    // This is evidence of a syntax error in the incoming SQL.
    DLOG(FATAL) << "SQL compile error " << GetErrorMessage();
    return new StatementRef(NULL, NULL, false);
  }
  return new StatementRef(NULL, stmt, true);
}

std::string Connection::GetSchema() const {
  // The ORDER BY should not be necessary, but relying on organic
  // order for something like this is questionable.
  const char* kSql =
      "SELECT type, name, tbl_name, sql "
      "FROM sqlite_master ORDER BY 1, 2, 3, 4";
  Statement statement(GetUntrackedStatement(kSql));

  std::string schema;
  while (statement.Step()) {
    schema += statement.ColumnString(0);
    schema += '|';
    schema += statement.ColumnString(1);
    schema += '|';
    schema += statement.ColumnString(2);
    schema += '|';
    schema += statement.ColumnString(3);
    schema += '\n';
  }

  return schema;
}

bool Connection::IsSQLValid(const char* sql) {
  AssertIOAllowed();
  if (!db_) {
    DLOG_IF(FATAL, !poisoned_) << "Illegal use of connection without a db";
    return false;
  }

  sqlite3_stmt* stmt = NULL;
  if (sqlite3_prepare_v2(db_, sql, -1, &stmt, NULL) != SQLITE_OK)
    return false;

  sqlite3_finalize(stmt);
  return true;
}

bool Connection::DoesTableExist(const char* table_name) const {
  return DoesTableOrIndexExist(table_name, "table");
}

bool Connection::DoesIndexExist(const char* index_name) const {
  return DoesTableOrIndexExist(index_name, "index");
}

bool Connection::DoesTableOrIndexExist(
    const char* name, const char* type) const {
  const char* kSql = "SELECT name FROM sqlite_master WHERE type=? AND name=?";
  Statement statement(GetUntrackedStatement(kSql));
  statement.BindString(0, type);
  statement.BindString(1, 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(")");

  Statement statement(GetUntrackedStatement(sql.c_str()));
  while (statement.Step()) {
    if (!statement.ColumnString(1).compare(column_name))
      return true;
  }
  return false;
}

int64 Connection::GetLastInsertRowId() const {
  if (!db_) {
    DLOG_IF(FATAL, !poisoned_) << "Illegal use of connection without a db";
    return 0;
  }
  return sqlite3_last_insert_rowid(db_);
}

int Connection::GetLastChangeCount() const {
  if (!db_) {
    DLOG_IF(FATAL, !poisoned_) << "Illegal use of connection without a db";
    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,
                              Connection::Retry retry_flag) {
  AssertIOAllowed();

  if (db_) {
    DLOG(FATAL) << "sql::Connection is already open.";
    return false;
  }

  // Make sure sqlite3_initialize() is called before anything else.
  InitializeSqlite();

  // If |poisoned_| is set, it means an error handler called
  // RazeAndClose().  Until regular Close() is called, the caller
  // should be treating the database as open, but is_open() currently
  // only considers the sqlite3 handle's state.
  // TODO(shess): Revise is_open() to consider poisoned_, and review
  // to see if any non-testing code even depends on it.
  DLOG_IF(FATAL, poisoned_) << "sql::Connection is already open.";
  poisoned_ = false;

  int err = sqlite3_open(file_name.c_str(), &db_);
  if (err != SQLITE_OK) {
    // Extended error codes cannot be enabled until a handle is
    // available, fetch manually.
    err = sqlite3_extended_errcode(db_);

    // Histogram failures specific to initial open for debugging
    // purposes.
    UMA_HISTOGRAM_SPARSE_SLOWLY("Sqlite.OpenFailure", err);

    OnSqliteError(err, NULL, "-- sqlite3_open()");
    bool was_poisoned = poisoned_;
    Close();

    if (was_poisoned && retry_flag == RETRY_ON_POISON)
      return OpenInternal(file_name, NO_RETRY);
    return false;
  }

  // TODO(shess): OS_WIN support?
#if defined(OS_POSIX)
  if (restrict_to_user_) {
    DCHECK_NE(file_name, std::string(":memory"));
    base::FilePath file_path(file_name);
    int mode = 0;
    // TODO(shess): Arguably, failure to retrieve and change
    // permissions should be fatal if the file exists.
    if (base::GetPosixFilePermissions(file_path, &mode)) {
      mode &= base::FILE_PERMISSION_USER_MASK;
      base::SetPosixFilePermissions(file_path, mode);

      // SQLite sets the permissions on these files from the main
      // database on create.  Set them here in case they already exist
      // at this point.  Failure to set these permissions should not
      // be fatal unless the file doesn't exist.
      base::FilePath journal_path(file_name + FILE_PATH_LITERAL("-journal"));
      base::FilePath wal_path(file_name + FILE_PATH_LITERAL("-wal"));
      base::SetPosixFilePermissions(journal_path, mode);
      base::SetPosixFilePermissions(wal_path, mode);
    }
  }
#endif  // defined(OS_POSIX)

  // SQLite uses a lookaside buffer to improve performance of small mallocs.
  // Chromium already depends on small mallocs being efficient, so we disable
  // this to avoid the extra memory overhead.
  // This must be called immediatly after opening the database before any SQL
  // statements are run.
  sqlite3_db_config(db_, SQLITE_DBCONFIG_LOOKASIDE, NULL, 0, 0);

  // 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";

  // sqlite3_open() does not actually read the database file (unless a
  // hot journal is found).  Successfully executing this pragma on an
  // existing database requires a valid header on page 1.
  // TODO(shess): For now, just probing to see what the lay of the
  // land is.  If it's mostly SQLITE_NOTADB, then the database should
  // be razed.
  err = ExecuteAndReturnErrorCode("PRAGMA auto_vacuum");
  if (err != SQLITE_OK)
    UMA_HISTOGRAM_SPARSE_SLOWLY("Sqlite.OpenProbeFailure", err);

#if defined(OS_IOS) && defined(USE_SYSTEM_SQLITE)
  // The version of SQLite shipped with iOS doesn't enable ICU, which includes
  // REGEXP support. Add it in dynamically.
  err = sqlite3IcuInit(db_);
  DCHECK_EQ(err, SQLITE_OK) << "Could not enable ICU support";
#endif  // OS_IOS && USE_SYSTEM_SQLITE

  // 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 failure.  Code which
    // requests exclusive locking but doesn't get it is almost certain
    // to be ill-tested.
    ignore_result(Execute("PRAGMA locking_mode=EXCLUSIVE"));
  }

  // http://www.sqlite.org/pragma.html#pragma_journal_mode
  // DELETE (default) - delete -journal file to commit.
  // TRUNCATE - truncate -journal file to commit.
  // PERSIST - zero out header of -journal file to commit.
  // journal_size_limit provides size to trim to in PERSIST.
  // TODO(shess): Figure out if PERSIST and journal_size_limit really
  // matter.  In theory, it keeps pages pre-allocated, so if
  // transactions usually fit, it should be faster.
  ignore_result(Execute("PRAGMA journal_mode = PERSIST"));
  ignore_result(Execute("PRAGMA journal_size_limit = 16384"));

  const base::TimeDelta kBusyTimeout =
    base::TimeDelta::FromSeconds(kBusyTimeoutSeconds);

  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.";
    const int kSqliteMaxPageSize = 32768;  // from sqliteLimit.h
    DCHECK_LE(page_size_, kSqliteMaxPageSize);
    const std::string sql =
        base::StringPrintf("PRAGMA page_size=%d", page_size_);
    ignore_result(ExecuteWithTimeout(sql.c_str(), kBusyTimeout));
  }

  if (cache_size_ != 0) {
    const std::string sql =
        base::StringPrintf("PRAGMA cache_size=%d", cache_size_);
    ignore_result(ExecuteWithTimeout(sql.c_str(), kBusyTimeout));
  }

  if (!ExecuteWithTimeout("PRAGMA secure_delete=ON", kBusyTimeout)) {
    bool was_poisoned = poisoned_;
    Close();
    if (was_poisoned && retry_flag == RETRY_ON_POISON)
      return OpenInternal(file_name, NO_RETRY);
    return false;
  }

  return true;
}

void Connection::DoRollback() {
  Statement rollback(GetCachedStatement(SQL_FROM_HERE, "ROLLBACK"));
  rollback.Run();
  needs_rollback_ = false;
}

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())
    DLOG(FATAL) << "Could not find statement";
  else
    open_statements_.erase(i);
}

void Connection::AddTaggedHistogram(const std::string& name,
                                    size_t sample) const {
  if (histogram_tag_.empty())
    return;

  // TODO(shess): The histogram macros create a bit of static storage
  // for caching the histogram object.  This code shouldn't execute
  // often enough for such caching to be crucial.  If it becomes an
  // issue, the object could be cached alongside histogram_prefix_.
  std::string full_histogram_name = name + "." + histogram_tag_;
  base::HistogramBase* histogram =
      base::SparseHistogram::FactoryGet(
          full_histogram_name,
          base::HistogramBase::kUmaTargetedHistogramFlag);
  if (histogram)
    histogram->Add(sample);
}

int Connection::OnSqliteError(int err, sql::Statement *stmt, const char* sql) {
  UMA_HISTOGRAM_SPARSE_SLOWLY("Sqlite.Error", err);
  AddTaggedHistogram("Sqlite.Error", err);

  // Always log the error.
  if (!sql && stmt)
    sql = stmt->GetSQLStatement();
  if (!sql)
    sql = "-- unknown";
  LOG(ERROR) << histogram_tag_ << " sqlite error " << err
             << ", errno " << GetLastErrno()
             << ": " << GetErrorMessage()
             << ", sql: " << sql;

  if (!error_callback_.is_null()) {
    // Fire from a copy of the callback in case of reentry into
    // re/set_error_callback().
    // TODO(shess): <http://crbug.com/254584>
    ErrorCallback(error_callback_).Run(err, stmt);
    return err;
  }

  // The default handling is to assert on debug and to ignore on release.
  if (!ShouldIgnoreSqliteError(err))
    DLOG(FATAL) << GetErrorMessage();
  return err;
}

bool Connection::FullIntegrityCheck(std::vector<std::string>* messages) {
  return IntegrityCheckHelper("PRAGMA integrity_check", messages);
}

bool Connection::QuickIntegrityCheck() {
  std::vector<std::string> messages;
  if (!IntegrityCheckHelper("PRAGMA quick_check", &messages))
    return false;
  return messages.size() == 1 && messages[0] == "ok";
}

// TODO(shess): Allow specifying maximum results (default 100 lines).
bool Connection::IntegrityCheckHelper(
    const char* pragma_sql,
    std::vector<std::string>* messages) {
  messages->clear();

  // This has the side effect of setting SQLITE_RecoveryMode, which
  // allows SQLite to process through certain cases of corruption.
  // Failing to set this pragma probably means that the database is
  // beyond recovery.
  const char kWritableSchema[] = "PRAGMA writable_schema = ON";
  if (!Execute(kWritableSchema))
    return false;

  bool ret = false;
  {
    sql::Statement stmt(GetUniqueStatement(pragma_sql));

    // The pragma appears to return all results (up to 100 by default)
    // as a single string.  This doesn't appear to be an API contract,
    // it could return separate lines, so loop _and_ split.
    while (stmt.Step()) {
      std::string result(stmt.ColumnString(0));
      base::SplitString(result, '\n', messages);
    }
    ret = stmt.Succeeded();
  }

  // Best effort to put things back as they were before.
  const char kNoWritableSchema[] = "PRAGMA writable_schema = OFF";
  ignore_result(Execute(kNoWritableSchema));

  return ret;
}

}  // namespace sql
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root/sql/connection.cc

DEFINITIONS
