Bug #80761 [Com]: PDO uses too much memory

Edit report at https://bugs.php.net/bug.php?id=80761&edit=1 ID: 80761 Comment by: dharman@php.net Reported by: anton at 4blk dot com Summary: PDO uses too much memory Status: Open Type: Bug Package: PDO MySQL Operating System: Ubuntu 16.04 PHP Version: 7.3.27 Block user comment: N Private report: N New Comment: I don't think this is PDO specific. I believe this is just how mysqlnd allocates memory. It would be worth looking into it in more detail to see if this could be improved. Previous Comments: ------------------------------------------------------------------------ [2021-02-17 09:30:59] anton at 4blk dot com Description: ------------ Fetching long strings or BLOBs from MySQL uses too much memory. Creating 100 MB string in php uses ~100 MB memory. Fetching 100 MB string from database uses ~600 MB memory. Test script: --------------- <?php // docker run --net=host --name db -e MYSQL_ALLOW_EMPTY_PASSWORD=yes -d mysql:5 --max_allowed_packet=256M ini_set('memory_limit', -1); $mb = 1024**2; $n = 100 * $mb; // $x = str_repeat('a', $n); $db = new pdo('mysql:host=127.0.0.1;port=3306', 'root', '', [PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION]); $x = $db->query("select repeat('a', $n)"); printf("%.2F\n", memory_get_peak_usage() / $mb); Expected result: ---------------- ~100 MB Actual result: -------------- ~600 MB ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=80761&edit=1