getSelectColumnsSQL example

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
                : $filterSql;
        }

        $select = 'SELECT ' . $columnList;