src/Collection/Type.php
public function executeIds()
    {
        if (!$this->isReady()) {
            throw new LogicException('Collection is not ready');
        }

        if ($this->ids === false) {
            $this->ids = $this->connection->executeFirstColumn($this->getSelectSql(false));

            if (empty($this->ids)) {
                $this->ids = [];
            }
        }

        return $this->ids;
    }
public function executeIds()
    {
        if (!$this->isReady()) {
            throw new LogicException('Collection is not ready');
        }

        if ($this->ids === false) {
            $this->ids = $this->connection->executeFirstColumn($this->getSelectSql(false));

            if (empty($this->ids)) {
                $this->ids = [];
            }
        }

        return $this->ids;
    }
Return ID-s of matching records.

@return array