From a97402559b540052fc54ddce830cca1f5d7464a2 Mon Sep 17 00:00:00 2001
From: Aaron Schulz <aschulz@wikimedia.org>
Date: Thu, 14 Nov 2013 23:23:36 -0800
Subject: [PATCH] Changed use of tag_summary to use change_tag with
 GROUP_CONCAT()

* Added buildGroupConcatField() method to the DB classes

bug: 53577
Change-Id: I976f297653880e66af429ba9b622a954fefcc512
---
 includes/ChangeTags.php          |  7 +++----
 includes/db/Database.php         | 23 +++++++++++++++++++++++
 includes/db/DatabaseOracle.php   |  7 +++++++
 includes/db/DatabasePostgres.php |  7 +++++++
 includes/db/DatabaseSqlite.php   |  7 +++++++
 5 files changed, 47 insertions(+), 4 deletions(-)

diff --git a/includes/ChangeTags.php b/includes/ChangeTags.php
index 7ec641d9d6..3c734c4e69 100644
--- a/includes/ChangeTags.php
+++ b/includes/ChangeTags.php
@@ -193,10 +193,9 @@ class ChangeTags {
 			throw new MWException( 'Unable to determine appropriate JOIN condition for tagging.' );
 		}
 
-		// JOIN on tag_summary
-		$tables[] = 'tag_summary';
-		$join_conds['tag_summary'] = array( 'LEFT JOIN', "ts_$join_cond=$join_cond" );
-		$fields[] = 'ts_tags';
+		$fields['ts_tags'] = wfGetDB( DB_SLAVE )->buildGroupConcatField(
+			',', 'change_tag', 'ct_tag', "ct_$join_cond=$join_cond"
+		);
 
 		if ( $wgUseTagFilter && $filter_tag ) {
 			// Somebody wants to filter on a tag.
diff --git a/includes/db/Database.php b/includes/db/Database.php
index c677d7437a..e2c59edb6b 100644
--- a/includes/db/Database.php
+++ b/includes/db/Database.php
@@ -2079,6 +2079,29 @@ abstract class DatabaseBase implements IDatabase, DatabaseType {
 		return 'CONCAT(' . implode( ',', $stringList ) . ')';
 	}
 
+	/**
+	 * Build a GROUP_CONCAT or equivalent statement for a query.
+	 *
+	 * This is useful for combining a field for several rows into a single string.
+	 * NULL values will not appear in the output, duplicated values will appear,
+	 * and the resulting delimiter-separated values have no defined sort order.
+	 * Code using the results may need to use the PHP unique() or sort() methods.
+	 *
+	 * @param string $delim Glue to bind the results together
+	 * @param string|array $table Table name
+	 * @param string $field Field name
+	 * @param string|array $conds Conditions
+	 * @param string|array $join_conds Join conditions
+	 * @return String SQL text
+	 * @since 1.23
+	 */
+	public function buildGroupConcatField(
+		$delim, $table, $field, $conds = '', $join_conds = array()
+	) {
+		$fld = "GROUP_CONCAT($field SEPARATOR " . $this->addQuotes( $delim ) . ')';
+		return '(' . $this->selectSQLText( $table, $fld, $conds, null, array(), $join_conds ) . ')';
+	}
+
 	/**
 	 * Change the current database
 	 *
diff --git a/includes/db/DatabaseOracle.php b/includes/db/DatabaseOracle.php
index 97070fb863..6b4113e9a1 100644
--- a/includes/db/DatabaseOracle.php
+++ b/includes/db/DatabaseOracle.php
@@ -1354,6 +1354,13 @@ class DatabaseOracle extends DatabaseBase {
 		return $this->mServer;
 	}
 
+	public function buildGroupConcatField(
+		$delim, $table, $field, $conds = '', $join_conds = array()
+	) {
+		$fld = "LISTAGG($field," . $this->addQuotes( $delim ) . ") WITHIN GROUP (ORDER BY $field)";
+		return '(' . $this->selectSQLText( $table, $fld, $conds, null, array(), $join_conds ) . ')';
+	}
+
 	public function getSearchEngine() {
 		return 'SearchOracle';
 	}
diff --git a/includes/db/DatabasePostgres.php b/includes/db/DatabasePostgres.php
index 72371a25a8..46880009cd 100644
--- a/includes/db/DatabasePostgres.php
+++ b/includes/db/DatabasePostgres.php
@@ -1431,6 +1431,13 @@ SQL;
 		return implode( ' || ', $stringList );
 	}
 
+	public function buildGroupConcatField(
+		$delimiter, $table, $field, $conds = '', $options = array(), $join_conds = array()
+	) {
+		$fld = "array_to_string(array_agg($field)," . $this->addQuotes( $delimiter ) . ')';
+		return '(' . $this->selectSQLText( $table, $fld, $conds, null, array(), $join_conds ) . ')';
+	}
+
 	public function getSearchEngine() {
 		return 'SearchPostgres';
 	}
diff --git a/includes/db/DatabaseSqlite.php b/includes/db/DatabaseSqlite.php
index 79a3b1ecf3..84f1bcf3b4 100644
--- a/includes/db/DatabaseSqlite.php
+++ b/includes/db/DatabaseSqlite.php
@@ -828,6 +828,13 @@ class DatabaseSqlite extends DatabaseBase {
 		return '(' . implode( ') || (', $stringList ) . ')';
 	}
 
+	public function buildGroupConcatField(
+		$delim, $table, $field, $conds = '', $join_conds = array()
+	) {
+		$fld = "group_concat($field," . $this->addQuotes( $delim ) . ')';
+		return '(' . $this->selectSQLText( $table, $fld, $conds, null, array(), $join_conds ) . ')';
+	}
+
 	/**
 	 * @throws MWException
 	 * @param $oldName
-- 
2.20.1