app/sql/connection.cc

// Copyright (c) 2009 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 "app/sql/connection.h"

#include <string.h>

#include "app/sql/statement.h"
#include "base/file_path.h"
#include "base/logging.h"
#include "base/string_util.h"
#include "third_party/sqlite/preprocessed/sqlite3.h"

namespace sql {

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_(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::Init(const FilePath& path) {
#if defined(OS_WIN)
  // We want the default encoding to always be UTF-8, so we use the
  // 8-bit version of open().
  int err = sqlite3_open(WideToUTF8(path.value()).c_str(), &db_);
#elif defined(OS_POSIX)
  int err = sqlite3_open(path.value().c_str(), &db_);
#endif

  if (err != SQLITE_OK) {
    db_ = NULL;
    return false;
  }

  if (page_size_ != 0) {
    if (!Execute(StringPrintf("PRAGMA page_size=%d", page_size_).c_str()))
      NOTREACHED() << "Could not set page size";
  }

  if (cache_size_ != 0) {
    if (!Execute(StringPrintf("PRAGMA cache_size=%d", cache_size_).c_str()))
      NOTREACHED() << "Could not set page size";
  }

  if (exclusive_locking_) {
    if (!Execute("PRAGMA locking_mode=EXCLUSIVE"))
      NOTREACHED() << "Could not set locking mode.";
  }

  return true;
}

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.Run())
    return;

  sqlite3Preload(db_);
}

bool Connection::BeginTransaction() {
  if (needs_rollback_) {
    DCHECK(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 nonexistant 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 nonexistant 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::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_);
}

const char* Connection::GetErrorMessage() const {
  if (!db_)
    return "sql::Connection has no connection.";
  return sqlite3_errmsg(db_);
}

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();
}

}  // namespace sql