From: Aaron Schulz <aaron@users.mediawiki.org>
Date: Tue, 22 Mar 2011 13:11:28 +0000 (+0000)
Subject: * Avoid adding DISTINCT if possible
X-Git-Tag: 1.31.0-rc.0~31252
X-Git-Url: https://git.cyclocoop.org/%28%28?a=commitdiff_plain;h=45191d2a50d5559025ddc6f09537deb8c75f3b5e;p=lhc%2Fweb%2Fwiklou.git

* Avoid adding DISTINCT if possible
* Added comments
---

diff --git a/includes/LogEventsList.php b/includes/LogEventsList.php
index 9fd82848eb..2d918ed25f 100644
--- 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';
 	}