From 89d5f0ef61d8ec22a07cbd521393d2c91356c79f Mon Sep 17 00:00:00 2001
From: Aaron Schulz <aschulz@wikimedia.org>
Date: Fri, 17 Apr 2015 13:04:35 -0700
Subject: [PATCH] Reduce change for deadlocks in Block::insert()

Bug: T96428
Change-Id: Idb266c8de7b5d7d85339ecc58044c28005527c89
---
 includes/Block.php | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/includes/Block.php b/includes/Block.php
index 0e2188dba2..76667511b8 100644
--- a/includes/Block.php
+++ b/includes/Block.php
@@ -443,11 +443,15 @@ class Block {
 
 		$dbw->insert( 'ipblocks', $row, __METHOD__, array( 'IGNORE' ) );
 		$affected = $dbw->affectedRows();
+		$this->mId = $dbw->insertId();
 
 		# Don't collide with expired blocks.
-		# Do this after trying to insert to avoid pointless gap locks.
+		# Do this after trying to insert to avoid locking.
 		if ( !$affected ) {
-			$dbw->delete( 'ipblocks',
+			# T96428: The ipb_address index uses a prefix on a field, so
+			# use a standard SELECT + DELETE to avoid annoying gap locks.
+			$ids = $dbw->selectFieldValues( 'ipblocks',
+				'ipb_id',
 				array(
 					'ipb_address' => $row['ipb_address'],
 					'ipb_user' => $row['ipb_user'],
@@ -455,13 +459,14 @@ class Block {
 				),
 				__METHOD__
 			);
-
-			$dbw->insert( 'ipblocks', $row, __METHOD__, array( 'IGNORE' ) );
-			$affected = $dbw->affectedRows();
+			if ( $ids ) {
+				$dbw->delete( 'ipblocks', array( 'ipb_id' => $ids ), __METHOD__ );
+				$dbw->insert( 'ipblocks', $row, __METHOD__, array( 'IGNORE' ) );
+				$affected = $dbw->affectedRows();
+				$this->mId = $dbw->insertId();
+			}
 		}
 
-		$this->mId = $dbw->insertId();
-
 		if ( $affected ) {
 			$auto_ipd_ids = $this->doRetroactiveAutoblock();
 			return array( 'id' => $this->mId, 'autoIds' => $auto_ipd_ids );
-- 
2.20.1