From 7055d6416d6c3c19e3a02e5be0e3f29cf1da48ff Mon Sep 17 00:00:00 2001
From: Max Semenik <maxsem@users.mediawiki.org>
Date: Wed, 21 Oct 2009 12:21:09 +0000
Subject: [PATCH] (bug 20268) Fixed Database::estimateRowCount on SQLite
 backend. This involved moving the previous implementation to where it belongs
 - DatabaseMysql, and replacing it with slightly tweaked DB2 implementation.

---
 RELEASE-NOTES                   |  1 +
 includes/db/Database.php        | 32 ++++++++++++++++----------------
 includes/db/DatabaseIbm_db2.php | 24 +-----------------------
 includes/db/DatabaseMssql.php   | 16 ----------------
 includes/db/DatabaseMysql.php   | 24 ++++++++++++++++++++++++
 5 files changed, 42 insertions(+), 55 deletions(-)

diff --git a/RELEASE-NOTES b/RELEASE-NOTES
index f89cc3ce60..8e81535ac3 100644
--- a/RELEASE-NOTES
+++ b/RELEASE-NOTES
@@ -580,6 +580,7 @@ it from source control: http://www.mediawiki.org/wiki/Download_from_SVN
 * (bug 20847) Deprecated deprecated akeytt() removed in wikibits.js leaving
   dummy
 * (bug 21161) Changing $wgCaCacheEpoch now always invalidates file cache
+* (bug 20268) Fixed row count estimation on SQLite backend
 
 == API changes in 1.16 ==
 
diff --git a/includes/db/Database.php b/includes/db/Database.php
index c8deb337e9..e9e87535da 100644
--- a/includes/db/Database.php
+++ b/includes/db/Database.php
@@ -961,26 +961,26 @@ abstract class DatabaseBase {
 	
 	/**
 	 * Estimate rows in dataset
-	 * Returns estimated count, based on EXPLAIN output
+	 * Returns estimated count - not necessarily an accurate estimate across different databases,
+	 * so use sparingly
 	 * Takes same arguments as Database::select()
+	 *
+	 * @param string $table table name
+	 * @param array $vars unused
+	 * @param array $conds filters on the table
+	 * @param string $fname function name for profiling
+	 * @param array $options options for select
+	 * @return int row count
 	 */
 	public function estimateRowCount( $table, $vars='*', $conds='', $fname = 'Database::estimateRowCount', $options = array() ) {
-		$options['EXPLAIN'] = true;
-		$res = $this->select( $table, $vars, $conds, $fname, $options );
-		if ( $res === false )
-			return false;
-		if ( !$this->numRows( $res ) ) {
-			$this->freeResult($res);
-			return 0;
+		$rows = 0;
+		$res = $this->select ( $table, 'COUNT(*) AS rowcount', $conds, $fname, $options );
+		if ( $res ) {
+			$row = $this->fetchRow( $res );
+			$rows = ( isset( $row['rowcount'] ) ) ? $row['rowcount'] : 0;
 		}
-
-		$rows = 1;
-		while( $plan = $this->fetchObject( $res ) ) {
-			$rows *= $plan->rows > 0 ? $plan->rows : 1; // avoid resetting to zero
-		}
-
-		$this->freeResult($res);
-		return $rows;		
+		$this->freeResult( $res );
+		return $rows;
 	}
 
 	/**
diff --git a/includes/db/DatabaseIbm_db2.php b/includes/db/DatabaseIbm_db2.php
index ed493e299a..b6866c5b22 100644
--- a/includes/db/DatabaseIbm_db2.php
+++ b/includes/db/DatabaseIbm_db2.php
@@ -1662,29 +1662,7 @@ SQL;
 
 		$this->query( $sql, $fname );
 	}
-	
-	/**
-	 * Estimate rows in dataset
-	 * Returns estimated count, based on COUNT(*) output
-	 * Takes same arguments as Database::select()
-	 * @param string $table table name
-	 * @param array $vars unused
-	 * @param array $conds filters on the table
-	 * @param string $fname function name for profiling
-	 * @param array $options options for select
-	 * @return int row count
-	 */
-	public function estimateRowCount( $table, $vars='*', $conds='', $fname = 'Database::estimateRowCount', $options = array() ) {
-		$rows = 0;
-		$res = $this->select ($table, 'COUNT(*) as mwrowcount', $conds, $fname, $options );
-		if ($res) {
-			$row = $this->fetchRow($res);
-			$rows = (isset($row['mwrowcount'])) ? $row['mwrowcount'] : 0;
-		}
-		$this->freeResult($res);
-		return $rows;
-	}
-	
+
 	/**
 	 * Description is left as an exercise for the reader
 	 * @param mixed $b data to be encoded
diff --git a/includes/db/DatabaseMssql.php b/includes/db/DatabaseMssql.php
index 533d0cd7a0..923ffe4981 100644
--- a/includes/db/DatabaseMssql.php
+++ b/includes/db/DatabaseMssql.php
@@ -445,22 +445,6 @@ class DatabaseMssql extends DatabaseBase {
 		return $this->query( $sql, $fname );
 	}
 
-	/**
-	 * Estimate rows in dataset
-	 * Returns estimated count, based on EXPLAIN output
-	 * Takes same arguments as Database::select()
-	 */
-	function estimateRowCount( $table, $vars='*', $conds='', $fname = 'Database::estimateRowCount', $options = array() ) {
-		$rows = 0;
-		$res = $this->select ($table, 'COUNT(*)', $conds, $fname, $options );
-		if ($res) {
-			$row = $this->fetchObject($res);
-			$rows = $row[0];
-		}
-		$this->freeResult($res);
-		return $rows;
-	}
-	
 	/**
 	 * Determines whether a field exists in a table
 	 * Usually aborts on failure
diff --git a/includes/db/DatabaseMysql.php b/includes/db/DatabaseMysql.php
index 9727eaf1b3..40425466d7 100644
--- a/includes/db/DatabaseMysql.php
+++ b/includes/db/DatabaseMysql.php
@@ -229,6 +229,30 @@ class DatabaseMysql extends DatabaseBase {
 	}
 
 	function affectedRows() { return mysql_affected_rows( $this->mConn ); }
+	
+	/**
+	 * Estimate rows in dataset
+	 * Returns estimated count, based on EXPLAIN output
+	 * Takes same arguments as Database::select()
+	 */
+	public function estimateRowCount( $table, $vars='*', $conds='', $fname = 'Database::estimateRowCount', $options = array() ) {
+		$options['EXPLAIN'] = true;
+		$res = $this->select( $table, $vars, $conds, $fname, $options );
+		if ( $res === false )
+			return false;
+		if ( !$this->numRows( $res ) ) {
+			$this->freeResult($res);
+			return 0;
+		}
+
+		$rows = 1;
+		while( $plan = $this->fetchObject( $res ) ) {
+			$rows *= $plan->rows > 0 ? $plan->rows : 1; // avoid resetting to zero
+		}
+
+		$this->freeResult($res);
+		return $rows;		
+	}
 
 	function fieldInfo( $table, $field ) {
 		$table = $this->tableName( $table );
-- 
2.20.1