Bug #75402 [Opn->Csd]: Possible Memory Leak using PDO::CURSOR_SCROLL option

Edit report at https://bugs.php.net/bug.php?id=75402&edit=1 ID: 75402 Updated by: ab@php.net Reported by: olric86 at gmail dot com Summary: Possible Memory Leak using PDO::CURSOR_SCROLL option -Status: Open +Status: Closed Type: Bug Package: PDO PgSQL Operating System: Windows 10 PHP Version: 7.1.10 Block user comment: N Private report: N New Comment: Automatic comment on behalf of ab Revision: http://git.php.net/?p=php-src.git;a=commit;h=cc69950b1527b321bf54a9394938d57e8f5a35cc Log: Fixed bug #75402 Possible Memory Leak using PDO::CURSOR_SCROLL option Previous Comments: ------------------------------------------------------------------------ [2017-10-17 21:33:31] olric86 at gmail dot com Description: ------------ Hi, while migrating a project which was using PDO->MSSQL (https://docs.microsoft.com/it-it/sql/connect/php/microsoft-php-driver-for-sql-server) to PDO->PostgreSQL, I found a strange behavior in how memory is retained by PHP when prepared statements are 'prepared' with the \PDO::ATTR_CURSOR => \PDO::CURSOR_SCROLL option, at least on Microsoft Windows. By using the test script attached, it looks like memory used during the result set object retrieval is never de-allocated, leading to an abnormal memory consumption and ultimately to a httpd.exe crash on 32 bit systems due to memory allocation limitations. I'm using a x64 build of PHP 7.1.10 with Apache 2.4.28 on a Windows 10 x64 PRO and I've also tested the following with PHP 5.4 32 bit and with PHP 7.0 32bit. The behavior looks to be the same, each time the script is ran the memory used by httpd.exe increments by almost 800KB and it never get released. We saw processes keeping up to 1.5Gb of RAM on 32bit OSs. By simply changing the prepared statement 'prepare' option to: \PDO::ATTR_CURSOR => \PDO::CURSOR_FWDONLY memory is allocated and de-allocated correctly. You can see here: https://drive.google.com/open?id=0Bx83lRq7kAiKY0ViRFJWMkxBZlE how quickly memory is being allocated and never released. Initially I thought it was some kind of caching mechanism of PHP/PDO/PGSQL but memory allocation seems to be simply increasing with no limit. This does not happen with the CURSOR_FWDONLY option. Please find a sample test script below. Test script: --------------- SQL Table creation script: https://drive.google.com/open?id=0Bx83lRq7kAiKSldZNEZ5QXh5R0E SQL Dummy data insert script: https://drive.google.com/open?id=0Bx83lRq7kAiKdTJRTERjQzh1NEk PHP test script: https://drive.google.com/open?id=0Bx83lRq7kAiKQWt5QTNHdmhPVmc ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=75402&edit=1