From 6131a214aa585d3cd0460551c2acd3927e930951 Mon Sep 17 00:00:00 2001
From: Brad Jorsch <bjorsch@wikimedia.org>
Date: Tue, 14 Jan 2014 15:36:48 -0500
Subject: [PATCH] pageid parser function is expensive, make it so

The pageid parser function (not to be confused with the pageid magic
word) hits the database for every title passed, which meets the criteria
for being considered an expensive parser function.

To mitigate this new expensiveness, check for special namespaces,
interwiki titles, and titles in LinkCache before hitting the DB.

Also, record potentially-valid titles in pagelinks so that the page can
be properly purged if the target is created/deleted.

Change-Id: I4fbfc265543f0a64c14dc8a44e1c89cd928a1adb
---
 includes/parser/CoreParserFunctions.php | 30 ++++++++++++++++++++++---
 1 file changed, 27 insertions(+), 3 deletions(-)

diff --git a/includes/parser/CoreParserFunctions.php b/includes/parser/CoreParserFunctions.php
index df0f1187cb..13feb80082 100644
--- a/includes/parser/CoreParserFunctions.php
+++ b/includes/parser/CoreParserFunctions.php
@@ -986,10 +986,34 @@ class CoreParserFunctions {
 		// Use title from parser to have correct pageid after edit
 		if ( $t->equals( $parser->getTitle() ) ) {
 			$t = $parser->getTitle();
+			return $t->getArticleID();
 		}
-		// fetch pageid from cache/database and return the value
-		$pageid = $t->getArticleID();
-		return $pageid ? $pageid : '';
+
+		// These can't have ids
+		if ( !$t->canExist() || $t->isExternal() ) {
+			return 0;
+		}
+
+		// Check the link cache, maybe something already looked it up.
+		$linkCache = LinkCache::singleton();
+		$pdbk = $t->getPrefixedDBkey();
+		$id = $linkCache->getGoodLinkID( $pdbk );
+		if ( $id != 0 ) {
+			$parser->mOutput->addLink( $t, $id );
+			return $id;
+		}
+		if ( $linkCache->isBadLink( $pdbk ) ) {
+			$parser->mOutput->addLink( $t, 0 );
+			return $id;
+		}
+
+		// We need to load it from the DB, so mark expensive
+		if ( $parser->incrementExpensiveFunctionCount() ) {
+			$id = $t->getArticleID();
+			$parser->mOutput->addLink( $t, $id );
+			return $id;
+		}
+		return null;
 	}
 
 	/**
-- 
2.20.1