Bug #52959 [Opn->Csd]: PDO_MYSQL: Memory leak when unsetting PDOStatement and/or resultset

Edit report at https://bugs.php.net/bug.php?id=52959&edit=1 ID: 52959 Updated by: nikic@php.net Reported by: eddawley at gmail dot com Summary: PDO_MYSQL: Memory leak when unsetting PDOStatement and/or resultset -Status: Open +Status: Closed Type: Bug Package: PDO MySQL Operating System: Centos 5 PHP Version: 5.3.3 -Assigned To: +Assigned To: nikic Block user comment: N Private report: N New Comment: Can't reproduce this with any combination of unsets commented or not. Presumably this has been fixed since this issue was reported ten years ago... Previous Comments: ------------------------------------------------------------------------ [2010-09-29 23:45:06] eddawley at gmail dot com Description: ------------ I am noticing unexpected, inconsistent memory use when unsetting the resultset of a PDOStatement and/or unsetting the statement itself. I have attached a quick test script to illustrate the problematic behavior. I am selecting approximately 500k rows in order to make the memory usage obvious. The script should be run with all of the unsets commented out and then with some or all uncommented. Run with: no unsets: system memory usage fluctuates but relatively stable, peak memory usage increases uncommenting some or all of the unsets: system and peak usage will continually increase I understand how the memory usage could fluctuate due to garbage collection but I do not understand why the addition of unsets would cause a steady increase in memory usage. This appears to be a memory leak. Also, top/ps output for RSS/VSZ of the process matches the "peak" memory usage and not the system allocated or php allocated numbers. Is this to be expected? Test script: --------------- <?php $db = connect(); while(1){ echo(memory_get_usage(true) . "\t" . memory_get_usage() . "\t" . memory_get_peak_usage() . "\n"); blah($db); } function blah($db){ $sql = "select id from table LIMIT 500000"; $stmt = $db->prepare($sql); $stmt->execute(); $a = $stmt->fetchAll(); //unset($a); $stmt->execute(); $a = $stmt->fetchAll(); //unset($a); //unset($stmt); } function connect(){ $dsn = 'mysql:host=127.0.0.1;dbname=db;port=3306'; $options = array(PDO::ATTR_TIMEOUT => APPLICATION_DB_PDO_TIMEOUT); $db = new PDO($dsn, 'user', 'pass', $options); return $db; } Expected result: ---------------- Memory usage over time should be relatively stable overall. Peak memory usage should be lowest when unsetting the first resultset. Actual result: -------------- Memory usage continues to increase over time if any of the unsets are uncommented. Peak memory usage is halved when the first resultset is unset but it continues to increase over time. ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=52959&edit=1