Last updated: Fri, 01 Jun 2007

mysql_free_result

(PHP 4, PHP 5, PECL mysql:1.0)

mysql_free_result — Free result memory

Description

bool mysql_free_result ( resource $result )

mysql_free_result() will free all memory associated with the result identifier result.

mysql_free_result() only needs to be called if you are concerned about how much memory is being used for queries that return large result sets. All associated result memory is automatically freed at the end of the script's execution.

Parameters

result: The result resource that is being evaluated. This result comes from a call to mysql_query().

Return Values

Returns TRUE on success or FALSE on failure.

If a non-resource is used for the result, an error of level E_WARNING will be emitted. It's worth noting that mysql_query() only returns a resource for SELECT, SHOW, EXPLAIN, and DESCRIBE queries.

Examples

Example 1398. A mysql_free_result() example


<?php

$result = mysql_query("SELECT id,email FROM people WHERE id = '42'");

if (!$result) {

    echo 'Could not run query: ' . mysql_error();

    exit;

}

/* Use the result, assuming we're done with it afterwords */

$row = mysql_fetch_assoc($result);



/* Now we free up the result and continue on with our script */

mysql_free_result($result);



echo $row['id'];

echo $row['email'];

?>

Notes

Note: For downward compatibility, the following deprecated alias may be used: mysql_freeresult()


ALWAYS use this function! I just encountered a bug in my code where I forgot to use this function. I also happen to be using mysql_pconnect() for a persistent connection. If you forget to free the result, it can hold the old result set open indefinitely within the HTTP process.



The upshot (in my application) was that I did updates that happened in a different HTTP process, but they mysteriously didn't show up in another HTTP process. After panicking that MySQL had mysterious data corruption and/or synchronization problems, I traced it back to this where an old result set was held open.

mdeininger at jyujin dot de
20-Sep-2005 11:45


yes, i encountered that too. as far as i could tell, that's because the script is stored in memory after being compiled and that's as much more memory as it needs for a call to that function.



if you always get lotsa data in your results, using this function will decrease memory usage tho, unless you use non-buffered queries (which are preferable unless you absolutely *have* to use mysql_seek(), or you need to do another query while the last one hasn't finished reporting back, as they can provide a small speedup)

macronesia at macronesia dot net
02-Jul-2005 07:11


You not need to use this if you are using PHP 4.



The comment below this comment may explain why it's actually costing more memory.

Joachim Kruyswijk
14-Jun-2005 09:42


Using this function may actually increase the amount of memory used. In my case, the script used 208 bytes less memory when *not* using mysql_free_result().

Check for yourself: call memory_get_usage() at the end of the script.

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