Bug #79661 [Fbk->Asn]: 2 Connections with different buffer stats cant run

Edit report at https://bugs.php.net/bug.php?id=79661&edit=1 ID: 79661 User updated by: thebluewalrus at gmail dot com Reported by: thebluewalrus at gmail dot com Summary: 2 Connections with different buffer stats cant run -Status: Feedback +Status: Assigned Type: Bug Package: PDO MySQL Operating System: Amazon Linux release 2 (Karoo) PHP Version: 7.3.18 Assigned To: cmb Block user comment: N Private report: N New Comment: Thanks. That worked, I think the documentation should be updated in this case. All documentation I've seen has it used as a boolean value. Previous Comments: ------------------------------------------------------------------------ [2020-06-01 15:31:45] cmb@php.net Instead of setting PDO::ATTR_PERSISTENT to true, you can set it to some arbitrary key; connections with different persistence keys will be separate. In your case, maybe use something like 'buffered' and 'unbuffered', respectively. ------------------------------------------------------------------------ [2020-06-01 15:13:06] thebluewalrus at gmail dot com Description: ------------ If 2 PDO connections are opened they seem to be merged. If the first is using unbuffered and second using buffered the first results in a buffered return. If both connections are using unbuffered and the first connection is running the second connection returns: Cannot execute queries while other unbuffered queries are active. Consider using PDOStatement::fetchAll(). Alternatively, if your code is only ever going to run against mysql, you may enable query buffering by setting the PDO::MYSQL_ATTR_USE_BUFFERED_QUERY attribute. on the first call. Issue produces on machines running 7.3.17 (OS Amazon Linux release 2 (Karoo)) and 7.1.33 (OS Red Hat Enterprise Linux Server release 7.3 (Maipo)). Test script: --------------- Case 1: $db = new PDO("mysql:host=".$dbhost.";dbname=".$dbname, $dbuser, $dbpass, array(PDO::ATTR_PERSISTENT => true, PDO::MYSQL_ATTR_USE_BUFFERED_QUERY => false)); $db_ub = new PDO("mysql:host=".$dbhost.";dbname=".$dbname, $dbuser, $dbpass, array(PDO::ATTR_PERSISTENT => true, PDO::MYSQL_ATTR_USE_BUFFERED_QUERY => true)); $stmt = $db->prepare('A QUERY THAT WILL EXCEED MEMORY LIMIT IF ALL ROWS RETURNED'); $stmt->execute(); while($row = $stmt->fetch(PDO::FETCH_ASSOC)) { //should run out of memory } Case 2: $db = new PDO("mysql:host=".$dbhost.";dbname=".$dbname, $dbuser, $dbpass, array(PDO::ATTR_PERSISTENT => true, PDO::MYSQL_ATTR_USE_BUFFERED_QUERY => false)); $db_ub = new PDO("mysql:host=".$dbhost.";dbname=".$dbname, $dbuser, $dbpass, array(PDO::ATTR_PERSISTENT => true, PDO::MYSQL_ATTR_USE_BUFFERED_QUERY => false)); $stmt = $db->prepare('A QUERY THAT WILL EXCEED MEMORY LIMIT IF ALL ROWS RETURNED'); $stmt->execute(); while($row = $stmt->fetch(PDO::FETCH_ASSOC)) { $stmt = $db_ub->prepare('select now()'); $stmt->execute(); } Expected result: ---------------- $stmt should only have 1 row at a time and memory usage should be low Actual result: -------------- Usually results in PHP Fatal error: Allowed memory size ... ini_set('memory_limit', can be used to get the script to run. ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=79661&edit=1