Add unique index for background job identifier

Author: Cyperghost

com.woltlab.wcf/package.xml

@@ -52,6 +52,7 @@
 
 	<!-- 
 	Required order of the following steps for the update to 6.2:
+	<instruction type="script">acp/update_com.woltlab.wcf_6.2_backgroundJob.php</instruction>
 	<instruction type="database" run="standalone">acp/database/update_com.woltlab.wcf_62_step1.php</instruction>
 	<instruction type="script">acp/update_com.woltlab.wcf_6.2_contactOptions.php</instruction>
 	<instruction type="database" run="standalone">acp/database/update_com.woltlab.wcf_62_step2.php</instruction>

wcfsetup/install/files/acp/database/update_com.woltlab.wcf_6.2_step1.php

@@ -10,12 +10,17 @@
 
 use wcf\system\database\table\column\IntDatabaseTableColumn;
 use wcf\system\database\table\column\MediumtextDatabaseTableColumn;
-use wcf\system\database\table\column\TextDatabaseTableColumn;
-use wcf\system\database\table\column\TinyintDatabaseTableColumn;
 use wcf\system\database\table\index\DatabaseTableForeignKey;
+use wcf\system\database\table\index\DatabaseTableIndex;
 use wcf\system\database\table\PartialDatabaseTable;
 
 return [
+    PartialDatabaseTable::create('wcf1_background_job')
+        ->indices([
+            DatabaseTableIndex::create('identifier')
+                ->type(DatabaseTableIndex::UNIQUE_TYPE)
+                ->columns(['identifier']),
+        ]),
     PartialDatabaseTable::create('wcf1_user')
         ->columns([
             IntDatabaseTableColumn::create('avatarFileID')

wcfsetup/install/files/acp/update_com.woltlab.wcf_6.2_backgroundJob.php

@@ -0,0 +1,21 @@
+<?php
+
+/**
+ * This script removes duplicate background jobs.
+ */
+
+use wcf\system\WCF;
+
+$sql = "DELETE background_jobs
+        FROM   wcf1_background_job background_jobs
+        JOIN   (
+            SELECT   MIN(jobID) as keepID, identifier
+            FROM     wcf1_background_job
+            WHERE    identifier IS NOT NULL
+            GROUP BY identifier
+            HAVING   COUNT(*) > 1
+        ) AS duplicates
+            ON background_jobs.identifier = duplicates.identifier
+        WHERE  background_jobs.jobID <> duplicates.keepID";
+$statement = WCF::getDB()->prepare($sql);
+$statement->execute();

wcfsetup/setup/db/install.sql

@@ -241,7 +241,7 @@ CREATE TABLE wcf1_background_job (
 	time INT(10) NOT NULL,
 	identifier VARCHAR(191) NULL,
 
-	KEY identifier (identifier),
+	UNIQUE KEY identifier (identifier),
 	KEY (status, time)
 );