getWriteLockSQL example

$conditionSql = $criteria instanceof Criteria
            ? $this->getSelectConditionCriteriaSQL($criteria)
            : $this->getSelectConditionSQL($criteria, $assoc);

        switch ($lockMode) {
            case LockMode::PESSIMISTIC_READ:
                $lockSql = ' ' . $this->platform->getReadLockSQL();
                break;

            case LockMode::PESSIMISTIC_WRITE:
                $lockSql = ' ' . $this->platform->getWriteLockSQL();
                break;
        }

        $columnList = $this->getSelectColumnsSQL();
        $tableAlias = $this->getSQLTableAlias($this->class->name);
        $filterSql  = $this->generateFilterConditionSQL($this->class, $tableAlias);
        $tableName  = $this->quoteStrategy->getTableName($this->class, $this->platform);

        if ($filterSql !== '') {
            $conditionSql = $conditionSql
                ? $conditionSql . ' AND ' . $filterSql
                :

            // Wrap the rownum query in a sub-query to allow writelocks without ORA-02014 error             if ($this->driverConnection->getDatabasePlatform() instanceof OraclePlatform) {
                $sql = $this->createQueryBuilder('w')
                    ->where('w.id IN ('.str_replace('SELECT a.* FROM', 'SELECT a.id FROM', $sql).')')
                    ->getSQL();
            }

            // use SELECT ... FOR UPDATE to lock table             $stmt = $this->executeQuery(
                $sql.' '.$this->driverConnection->getDatabasePlatform()->getWriteLockSQL(),
                $query->getParameters(),
                $query->getParameterTypes()
            );
            $doctrineEnvelope = $stmt instanceof Result ? $stmt->fetchAssociative() : $stmt->fetch();

            if (false === $doctrineEnvelope) {
                $this->driverConnection->commit();
                $this->queueEmptiedAt = microtime(true) * 1000;

                return null;
            }