Bug #65741 [Opn->Nab]: High memory usage from mysqli:query()

Edit report at https://bugs.php.net/bug.php?id=65741&edit=1 ID: 65741 Updated by: rasmus@php.net Reported by: cduncan at regatta dot com Summary: High memory usage from mysqli:query() -Status: Open +Status: Not a bug Type: Bug Package: MySQLi related Operating System: Linux PHP Version: 5.5.4 Block user comment: N Private report: N New Comment: The "appears to use" is key here. I bet you are using the mysqlnd driver now which means that the mysql library is using the PHP memory allocator which in turn means that memory_get_usage() is now able to see and track that memory. Before, using libmysqlclient, you were using just as much memory, but memory_get_usage() just couldn't see it. In fact, you were using more because it would get malloc'ed once by libmysqlclient and then when you fetched rows from PHP it would get copied to PHP-controlled memory. Now with the native driver that copy is no longer needed. Previous Comments: ------------------------------------------------------------------------ [2013-09-23 13:03:43] cduncan at regatta dot com Description: ------------ When executing a query that returns a large number of rows (around 16 million) the query() function appears to use a lot more memory than it did in version 5.3.8 I looked through the changelogs and couldn't find any obvious reason why, or any mention of a change in how the function works Test script: --------------- <?php $sql = new mysqli("localhost","username","password"); function checkMemory($key="") { $memory = round(memory_get_usage(true) / 1024 / 1024) . "mb"; echo "Memory " . $key . ": " . $memory . "\n"; } checkMemory("Before"); $query = "SELECT field1a, field2a, valb1, valb2, valb3, valb4 FROM test.table1 JOIN test.table2 ON companyb=companya AND field1b=field1a WHERE companya='TEST'"; $result = $sql->query($query); checkMemory("After"); $field = $result->fetch_field(); echo "End\n"; Expected result: ---------------- user@server:~$ /usr/local/php-5.3.8/bin/php memory.php Memory Before: 1mb Memory After: 1mb End Actual result: -------------- user@server:~$ /usr/local/php-5.5.4/bin/php memory.php Memory Before: 0mb Memory After: 427mb PHP Fatal error: Out of memory (allocated 1603796992) (tried to allocate 20 bytes) in /home/user/memory.php on line 17 ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=65741&edit=1