How to solve warning "fetchAll can be memory inefficient for large data sets" in magento2

Question

I am getting a warning as "fetch All can be memory inefficient for large data sets",
When I did MEQP2.
Please anyone can help me to resolve this warning.

I am getting a warning in below line

$expr = $this->zendExprFactory->create(['expression' => 'COUNT(*)']);

$productMappingQry = $connection->select()->from($this->resourceConfig->getTable($tableName), [$expr])->where('store=?', $storeId);

$finalData = $connection->fetchAll($Qry);

Thank you in advance

Answer 1

Try to use fetchOne

$expr = $this->zendExprFactory->create(['expression' => 'COUNT(*)']);

$productMappingQry = $connection->select()->from($this->resourceConfig->getTable($tableName), [$expr])->where('store=?', $storeId);

$finalData = $connection->fetchOne($Qry);

Answer 2

If there are multiple records, best practise for this situation

$rowSet = $this->_getReadAdapter()->fetchAll($select);
foreach ($rowSet as $row) {
 //process row
}

would be below one since it will fetch the rows one by one and reduce the memory utilization.

$query = $this->_getReadAdapter()->query($select);
while ($row = $query->fetch()) {
 //process row
}

Reference: https://info2.magento.com/rs/magentosoftware/images/Conquer_the_5_Most_Common_Magento_Coding_Issues_to_Optimize_Your_Site_for_Performance.pdf

Cheers!