From b9e51d16bca2eb0785503adacba76161588e9739 Mon Sep 17 00:00:00 2001
From: Brion Vibber <brion@users.mediawiki.org>
Date: Mon, 18 Sep 2006 17:52:44 +0000
Subject: [PATCH] * Lazy extraction of text chunks in Revision objects, may
 reduce hits to   external storage when actual text content is not used

---
 RELEASE-NOTES         |  2 ++
 includes/Revision.php | 27 +++++++++++++++++++--------
 2 files changed, 21 insertions(+), 8 deletions(-)

diff --git a/RELEASE-NOTES b/RELEASE-NOTES
index 0dbd206951..b484337e96 100644
--- a/RELEASE-NOTES
+++ b/RELEASE-NOTES
@@ -208,6 +208,8 @@ it from source control: http://www.mediawiki.org/wiki/Download_from_SVN
 * (bug 7309) Plurals: use singular form for zero in French and Brazilian Portuguese
 * Add page_no_title_convert field to support language variant conversion
   for page titles which shouldn't be converted on display/linking
+* Lazy extraction of text chunks in Revision objects, may reduce hits to
+  external storage when actual text content is not used
 
 
 == Languages updated ==
diff --git a/includes/Revision.php b/includes/Revision.php
index a33e48fefa..8591dc13c1 100644
--- a/includes/Revision.php
+++ b/includes/Revision.php
@@ -259,10 +259,13 @@ class Revision {
 				$this->mTitle = null;
 			}
 
+			// Lazy extraction...
+			$this->mText      = null;
 			if( isset( $row->old_text ) ) {
-				$this->mText  = $this->getRevisionText( $row );
+				$this->mTextRow = $row;
 			} else {
-				$this->mText  = null;
+				// 'text' table row entry will be lazy-loaded
+				$this->mTextRow = null;
 			}
 		} elseif( is_array( $row ) ) {
 			// Build a new revision to be saved...
@@ -668,14 +671,22 @@ class Revision {
 	function loadText() {
 		$fname = 'Revision::loadText';
 		wfProfileIn( $fname );
-
-		$dbr =& wfGetDB( DB_SLAVE );
-		$row = $dbr->selectRow( 'text',
-			array( 'old_text', 'old_flags' ),
-			array( 'old_id' => $this->getTextId() ),
-			$fname);
+		
+		// If we kept data for lazy extraction, use it now...
+		$row = $this->mTextRow;
+		$this->mTextRow = null;
+		
+		if( !$row ) {
+			// Text data is immutable; check slaves first.
+			$dbr =& wfGetDB( DB_SLAVE );
+			$row = $dbr->selectRow( 'text',
+				array( 'old_text', 'old_flags' ),
+				array( 'old_id' => $this->getTextId() ),
+				$fname);
+		}
 
 		if( !$row ) {
+			// Possible slave lag!
 			$dbw =& wfGetDB( DB_MASTER );
 			$row = $dbw->selectRow( 'text',
 				array( 'old_text', 'old_flags' ),
-- 
2.20.1