Merge "Introduce ContentAlterParserOutput hook"

[lhc/web/wiklou.git] / docs / database.txt

diff --git a/docs/database.txt b/docs/database.txt
index b9fa6ff..735f26b 100644 (file)
--- a/docs/database.txt
+++ b/docs/database.txt
@@ -7,8 +7,8 @@ By Tim Starling, January 2006.
 
 For information about the MediaWiki database layout, such as a 
 description of the tables and their contents, please see:
-  http://www.mediawiki.org/wiki/Manual:Database_layout
-  http://svn.wikimedia.org/viewvc/mediawiki/trunk/phase3/maintenance/tables.sql?view=markup
+  https://www.mediawiki.org/wiki/Manual:Database_layout
+  https://gerrit.wikimedia.org/r/gitweb?p=mediawiki/core.git;a=blob_plain;f=maintenance/tables.sql;hb=HEAD
 
 
 ------------------------------------------------------------------------
@@ -153,9 +153,9 @@ enclose small groups of queries in their own transaction. Use the
 following syntax:
 
 $dbw = wfGetDB( DB_MASTER );
-$dbw->begin();
+$dbw->begin( __METHOD__ );
 /* Do queries */
-$dbw->commit();
+$dbw->commit( __METHOD__ );
 
 Use of locking reads (e.g. the FOR UPDATE clause) is not advised. They
 are poorly implemented in InnoDB and will cause regular deadlock errors.
@@ -180,9 +180,19 @@ MediaWiki does support the following other DBMSs to varying degrees.
 * PostgreSQL
 * SQLite
 * Oracle
-* IBM DB2
 * MSSQL
 
 More information can be found about each of these databases (known issues,
 level of support, extra configuration) in the "databases" subdirectory in
 this folder.
+
+------------------------------------------------------------------------
+    Use of GROUP BY
+------------------------------------------------------------------------
+
+MySQL supports GROUP BY without checking anything in the SELECT clause. 
+Other DBMSs (especially Postgres) are stricter and require that all the 
+non-aggregate items in the SELECT clause appear in the GROUP BY. For 
+this reason, it is highly discouraged to use SELECT * with GROUP BY 
+queries.
+