From af58998190d5a3ac3079f015796bf167466b7781 Mon Sep 17 00:00:00 2001
From: Aaron Schulz <aschulz@wikimedia.org>
Date: Mon, 11 Apr 2016 14:01:43 -0700
Subject: [PATCH] Remove redundant UNIQUE from rev_page_id

The PRIMARY KEY is rev_id, so this is a waste and
makes the index slower to maintain (e.g. no change
buffering).

Bug: T142725
Change-Id: I63f817656ff5e62aa27caf607d70353cc99eb349
---
 includes/installer/MysqlUpdater.php           | 21 +++++++++++++++++++
 ...atch-revision-page-rev-index-nonunique.sql |  5 +++++
 maintenance/tables.sql                        |  2 +-
 3 files changed, 27 insertions(+), 1 deletion(-)
 create mode 100644 maintenance/archives/patch-revision-page-rev-index-nonunique.sql

diff --git a/includes/installer/MysqlUpdater.php b/includes/installer/MysqlUpdater.php
index 719b66aafb..6989969187 100644
--- a/includes/installer/MysqlUpdater.php
+++ b/includes/installer/MysqlUpdater.php
@@ -287,6 +287,7 @@ class MysqlUpdater extends DatabaseUpdater {
 			// 1.28
 			[ 'addIndex', 'recentchanges', 'rc_name_type_patrolled_timestamp',
 				'patch-add-rc_name_type_patrolled_timestamp_index.sql' ],
+			[ 'doRevisionPageRevIndexNonUnique' ]
 		];
 	}
 
@@ -1101,4 +1102,24 @@ class MysqlUpdater extends DatabaseUpdater {
 			'Making user_id unsigned int'
 		);
 	}
+
+	protected function doRevisionPageRevIndexNonUnique() {
+		if ( !$this->doTable( 'revision' ) ) {
+			return true;
+		} elseif ( !$this->db->indexExists( 'revision', 'rev_page_id' ) ) {
+			$this->output( "...rev_page_id index not found on revision.\n" );
+			return true;
+		}
+
+		if ( !$this->db->indexUnique( 'revision', 'rev_page_id' ) ) {
+			$this->output( "...rev_page_id index already non-unique.\n" );
+			return true;
+		}
+
+		return $this->applyPatch(
+			'patch-revision-page-rev-index-nonunique.sql',
+			false,
+			'Making rev_page_id index non-unique'
+		);
+	}
 }
diff --git a/maintenance/archives/patch-revision-page-rev-index-nonunique.sql b/maintenance/archives/patch-revision-page-rev-index-nonunique.sql
new file mode 100644
index 0000000000..dbb03257e1
--- /dev/null
+++ b/maintenance/archives/patch-revision-page-rev-index-nonunique.sql
@@ -0,0 +1,5 @@
+-- Makes rev_page_id index non-unique
+ALTER TABLE /*_*/revision
+DROP INDEX /*i*/rev_page_id;
+
+CREATE INDEX /*i*/rev_page_id ON /*_*/revision (rev_page, rev_id);
diff --git a/maintenance/tables.sql b/maintenance/tables.sql
index 40506bf3bd..b5c14e30f4 100644
--- a/maintenance/tables.sql
+++ b/maintenance/tables.sql
@@ -369,7 +369,7 @@ CREATE TABLE /*_*/revision (
 ) /*$wgDBTableOptions*/ MAX_ROWS=10000000 AVG_ROW_LENGTH=1024;
 -- In case tables are created as MyISAM, use row hints for MySQL <5.0 to avoid 4GB limit
 
-CREATE UNIQUE INDEX /*i*/rev_page_id ON /*_*/revision (rev_page, rev_id);
+CREATE INDEX /*i*/rev_page_id ON /*_*/revision (rev_page, rev_id);
 CREATE INDEX /*i*/rev_timestamp ON /*_*/revision (rev_timestamp);
 CREATE INDEX /*i*/page_timestamp ON /*_*/revision (rev_page,rev_timestamp);
 CREATE INDEX /*i*/user_timestamp ON /*_*/revision (rev_user,rev_timestamp);
-- 
2.20.1