mediawiki: do not clear session cache on every start (#507422)

pkgs/by-name/me/mediawiki/keep-session-object-cache.diff

@@ -0,0 +1,13 @@
+diff --git a/includes/Installer/DatabaseUpdater.php b/includes/Installer/DatabaseUpdater.php
+index 8ed996b9dee..733a3210096 100644
+--- a/includes/Installer/DatabaseUpdater.php
++++ b/includes/Installer/DatabaseUpdater.php
+@@ -1380,7 +1380,7 @@ public function purgeCache() {
+ 		// ObjectCache
+ 		$this->db->newDeleteQueryBuilder()
+ 			->deleteFrom( 'objectcache' )
+-			->where( ISQLPlatform::ALL_ROWS )
++			->where( "keyname NOT LIKE '%:MWSession:%'" )
+ 			->caller( __METHOD__ )
+ 			->execute();
+ 

pkgs/by-name/me/mediawiki/package.nix

@@ -14,6 +14,12 @@ stdenvNoCC.mkDerivation rec {
     hash = "sha256-XqjB8yHJ+Nuk0aweTsoYJ/sTUZ1KIZDiOfUUMgWKQmk=";
   };
 
+  patches = [
+    # NixOS runs the update script on every start as we might need to run some migrations.
+    # Normally this clears all active sessions, for usability we do not do that.
+    ./keep-session-object-cache.diff
+  ];
+
   postPatch = ''
     substituteInPlace includes/installer/CliInstaller.php \
       --replace-fail '$vars = Installer::getExistingLocalSettings();' '$vars = null;'