[wp-trac] [WordPress Trac] #23085: Calling $wpdb->query() when no connection exists causes mysql_error() to throw an error

[WordPress Trac]

#23085: Calling $wpdb->query() when no connection exists causes mysql_error() to
throw an error
------------------------------------+--------------------------
 Reporter:  mbijon                  |       Type:  defect (bug)
   Status:  new                     |   Priority:  normal
Milestone:  Awaiting Review         |  Component:  Database
  Version:  3.5                     |   Severity:  normal
 Keywords:  dev-feedback has-patch  |
------------------------------------+--------------------------
 In the query() method of wp-db.php, the mysql_error() expects that if a
 parameter is passed to it then it should be a valid link identifier.

 *May need feedback or added testing* ...this error may be specific to
 transactions, which is why it hasn't been noticed before. Unit tests do
 use transations and I only get these errors when ROLLBACK is called during
 specific unit tests that don't modify the DB state. A simple transaction
 opened & rolled back in the Debug Bar Console is not triggering this for
 me.

 Unit test failure examples:

 '''Test: test_is_image_positive'''

 {{{
 mysql_error() expects parameter 1 to be resource, integer given
 Execution time: 0.02507209777832s
 Stack Trace:
 Array
 (
     [0] => Array
         (
             [file] => C:\xampp\htdocs\wpnew\wp-includes\wp-db.php
             [line] => 1202
             [function] => mysql_error
             [args] => Array
                 (
                     [0] => 0
                 )

         )

     [1] => Array
         (
             [file] => C:\xampp\htdocs\wp_test_svn\includes\testcase.php
             [line] => 25
             [function] => query
             [class] => wpdb
             [type] => ->
             [args] => Array
                 (
                     [0] => ROLLBACK
                 )

         )

 )
 }}}

 '''Test: test_is_image_negative'''

 {{{
 mysql_error() expects parameter 1 to be resource, integer given
 Execution time: 0.02237606048584s
 Stack Trace:
 Array
 (
     [0] => Array
         (
             [file] => C:\xampp\htdocs\wpnew\wp-includes\wp-db.php
             [line] => 1202
             [function] => mysql_error
             [args] => Array
                 (
                     [0] => 0
                 )

         )

     [1] => Array
         (
             [file] => C:\xampp\htdocs\wp_test_svn\includes\testcase.php
             [line] => 25
             [function] => query
             [class] => wpdb
             [type] => ->
             [args] => Array
                 (
                     [0] => ROLLBACK
                 )

         )

 )
 }}}

 I don't think we should attempt {{{if ( $this->last_error = mysql_error()
 )}}}. That is because when mysql_error() is called without a link
 identifier then the most recent connection to MySQL is referenced. On a
 busy server this may not be the same connection as our page or transaction
 originally used. See #3544 for history/details.

-- 
Ticket URL: <http://core.trac.wordpress.org/ticket/23085>
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