Last modified: 2014-06-23 16:06:55 UTC

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Bug 50091 - PostgreSQL misuse of pg_get_result
PostgreSQL misuse of pg_get_result
Status: NEW
Product: MediaWiki
Classification: Unclassified
Database (Other open bugs)
All All
: Normal normal (vote)
: ---
Assigned To: Nobody - You can work on this!
Depends on:
Blocks: postgres
  Show dependency treegraph
Reported: 2013-06-24 12:25 UTC by Michael Allan
Modified: 2014-06-23 16:06 UTC (History)
2 users (show)

See Also:
Web browser: ---
Mobile Platform: ---
Assignee Huggle Beta Tester: ---


Description Michael Allan 2013-06-24 12:25:09 UTC
Shortly after upgrading PHP (to 5.4.13) and MediaWiki (to 1.21.1), I saw the following line in Apache's error log:

[Mon Jun 24 07:39:43 2013] [error] FastCGI: server "/var/www/localhost/cgi-bin/php.fcgi" stderr: PHP Notice:  pg_send_query(): There are results on this connection. Call pg_get_result() until it returns FALSE in /var/www/localhost/htdocs/mediawiki/includes/db/DatabasePostgres.php on line 441

Line 441 is the call to pg_send_query in here:

  public function doQuery( $sql ) {
      if ( function_exists( 'mb_convert_encoding' ) ) {
          $sql = mb_convert_encoding( $sql, 'UTF-8' );
      if( pg_send_query( $this->mConn, $sql ) === false ) {
          throw new DBUnexpectedError( $this, "Unable to post new query to PostgreSQL\n" );
      $this->mLastResult = pg_get_result( $this->mConn );
      $this->mAffectedRows = null;
      if ( pg_result_error( $this->mLastResult ) ) {
          return false;
      return $this->mLastResult;

I Googled and found the following thread:$26l3$$26l3$

If I understand, PHP has detected that the results of one query are still pending when a second query is issued.  To prevent this, it wants the results of each query to be cleared by *polling* pg_get_result() instead of making just a single call to that function.
Comment 1 Michael Allan 2013-06-24 17:04:10 UTC
I've since replicated the bug, but only in API requests aimed at Semantic MediaWiki 1.7.1 (action=ask).  Maybe that extension is the only source.

In any case, I'm now porting the affected wikis to MySQL.  SMW's support for postgres has tanked lately.
Comment 2 Marcin Cieślak 2013-07-17 14:18:50 UTC
Can you enable $wgDebugLogFile and $wgDebugDBTransactions and see what's there?
I wonder what kind of transitions do you get in this case.

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