Sphinx randomly fails to combine subqueries

Question

I have this sphinx search engine that I use through Zend using sphinxapi.php . It works fantastic. Really really great.

However, there is one problem: It randomly fails.

   // Prepare Sphinx search
   $sphinxClient = new SphinxClient();
   $sphinxClient->SetServer($ip, $port);
 $sphinxClient->SetConnectTimeout( 10 );

   $sphinxClient->SetMatchMode( SPH_MATCH_ANY  );
   $sphinxClient->SetLimits( $resultsPerPage * ($nPage - 1), $resultsPerPage );
 $sphinxClient->SetArrayResult( true );

 $query = array();
 $query['lang'] = '@lang "lang' . $language . '"';

 if (isset($params)) {
        foreach ($params as $param) {
   $query['tags'] = '@tags "' . $param . '"';
        }
 }

 // Make the Sphinx search
 $sphinxClient->SetMatchMode(SPH_MATCH_EXTENDED);
 $sphinxResult = $sphinxClient->Query(implode(' ', $query), '*');

As seen here, I search for a language and an arbitrary amount of tags, imploded into a single query string in the end (instead of making a battleload of subqueries).

So, normally, this works like a charm, but occassionally sphinx returns that it found 2000 entries in English and, say, 1000 entries with the tag "pictures" (or some other purely english word) but ZERO hits that fit both results, which is purely false. In fact, refreshing the page everything returns to normal with something like 800 real results.

My question is why does it do this and how do I make it stop?

Any ideas?

:Edit: Added shortened output log

    [error] => 
    [warning] => 
...
    [total] => 0 
    [total_found] => 0 
    [time] => 0.000 
    [words] => Array ( 
     [langen] => Array ( 
      [docs] => 2700 
      [hits] => 2701 ) 
     [picture] => Array ( 
      [docs] => 829 
      [hits] => 1571 ) ) )

Answer 1

have you checked to see if the sphinx client is giving you any error or warning messages that may describe the failure?

if($sphinxResult === false) {
    print "Query failed: " . $sphinxClient->GetLastError();
} else {
    if($sphinxClient->GetLastWarning()) {
        print "WARNING: " . $sphinxClient->GetLastWarning();
    }

    // process results
}