* Avoid adding DISTINCT if possible

* Added comments

diff --git a/includes/LogEventsList.php b/includes/LogEventsList.php
index 9fd8284..2d918ed 100644 (file)
--- a/includes/LogEventsList.php
+++ b/includes/LogEventsList.php
@@ -938,12 +938,21 @@ class LogPager extends ReverseChronologicalPager {
                $this->mConds[] = 'user_id = log_user';
                $index = array();
                $options = array();
-               # Add log_search table if there are conditions on it
-               if( array_key_exists('ls_field',$this->mConds) ) {
+               # Add log_search table if there are conditions on it.
+               # This filters the results to only include log rows that have
+               # log_search records with the specified ls_field and ls_value values.
+               if( array_key_exists( 'ls_field', $this->mConds ) ) {
                        $tables[] = 'log_search';
                        $index['log_search'] = 'ls_field_val';
                        $index['logging'] = 'PRIMARY';
-                       $options[] = 'DISTINCT';
+                       if ( !$this->hasEqualsClause( 'ls_field' )
+                               || !$this->hasEqualsClause( 'ls_value' ) )
+                       {
+                               # Since (ls_field,ls_value,ls_logid) is unique, if the condition is
+                               # to match a specific (ls_field,ls_value) tuple, then there will be
+                               # no duplicate log rows. Otherwise, we need to remove the duplicates.
+                               $options[] = 'DISTINCT';
+                       }
                # Avoid usage of the wrong index by limiting
                # the choices of available indexes. This mainly
                # avoids site-breaking filesorts.
@@ -967,7 +976,7 @@ class LogPager extends ReverseChronologicalPager {
                        'conds'      => $this->mConds,
                        'options'    => $options,
                        'join_conds' => array(
-                               'user' => array( 'INNER JOIN', 'user_id=log_user' ),
+                               'user'           => array( 'INNER JOIN', 'user_id=log_user' ),
                                'log_search' => array( 'INNER JOIN', 'ls_log_id=log_id' )
                        )
                );
@@ -977,6 +986,14 @@ class LogPager extends ReverseChronologicalPager {
                return $info;
        }
 
+       // Checks if $this->mConds has $field matched to a *single* value
+       protected function hasEqualsClause( $field ) {
+               return (
+                       array_key_exists( $field, $this->mConds ) &&
+                       ( !is_array( $this->mConds[$field] ) || count( $this->mConds[$field] ) == 1 )
+               );
+       }
+
        function getIndexField() {
                return 'log_timestamp';
        }