function DatabaseConnection_sqlite::nextId

Overrides DatabaseConnection::nextId

File

includes/database/sqlite/database.inc, line 302

Class

DatabaseConnection_sqlite

Specific SQLite implementation of DatabaseConnection.

Code

public function nextId($existing_id = 0) {
    $transaction = $this->startTransaction();
    // We can safely use literal queries here instead of the slower query
    // builder because if a given database breaks here then it can simply
    // override nextId. However, this is unlikely as we deal with short strings
    // and integers and no known databases require special handling for those
    // simple cases. If another transaction wants to write the same row, it will
    // wait until this transaction commits.
    $stmt = $this->query('UPDATE {sequences} SET value = GREATEST(value, :existing_id) + 1', array(
        ':existing_id' => $existing_id,
    ));
    if (!$stmt->rowCount()) {
        $this->query('INSERT INTO {sequences} (value) VALUES (:existing_id + 1)', array(
            ':existing_id' => $existing_id,
        ));
    }
    // The transaction gets committed when the transaction object gets destroyed
    // because it gets out of scope.
    return $this->query('SELECT value FROM {sequences}')
        ->fetchField();
}