Last modified: 2007-12-16 21:14:51 UTC

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Bug 10280 - For table categorylinks, add cl_from to the cl_sortkey index
For table categorylinks, add cl_from to the cl_sortkey index
Status: RESOLVED FIXED
Product: MediaWiki
Classification: Unclassified
Database (Other open bugs)
unspecified
All All
: Normal enhancement (vote)
: ---
Assigned To: Nobody - You can work on this!
: schema-change
Depends on:
Blocks:
  Show dependency treegraph
 
Reported: 2007-06-15 18:18 UTC by Yuri Astrakhan
Modified: 2007-12-16 21:14 UTC (History)
3 users (show)

See Also:
Web browser: ---
Mobile Platform: ---
Assignee Huggle Beta Tester: ---


Attachments

Description Yuri Astrakhan 2007-06-15 18:18:05 UTC
When API enumerates through the list of pages in a given category, it needs a way to resume the query. Sortkey provides a good point from which to continue, but has one drawback - more than one page may have identical one, which may lead to the following bug scenario:

Assuming there are 20 pages in a category, and page 10 and 11 both have identical sortkey, the user's query may request go 10 pages at a time. The sortkey to continue from would be the value of #11, but since it is the same as #10, #10 will be returned twice - in both the first and second resultset. This might even result in an infinite loop - requesting one item at a time would reach #10 and never advance to #11.

Solution:  sort by sortkey + cl_from, and store both the sortkey and cl_from as the starting point.

To optimize query execution, cl_sortkey needs to be modified by adding cl_from at the end:

ALTER TABLE `wikidb`.`categorylinks` DROP INDEX `cl_sortkey`,
 ADD INDEX `cl_sortkey` USING BTREE(`cl_to`, `cl_sortkey`, `cl_from`)
, ENGINE = MyISAM;
Comment 1 Yuri Astrakhan 2007-06-15 18:46:54 UTC
Checked in r23016 schema update. Pending servers update.
Comment 2 Yuri Astrakhan 2007-06-22 15:21:16 UTC
Another check-in r23228 - sql table scripts.
Comment 3 Jonathan 2007-09-15 01:13:19 UTC
This seems to contribute to the common http://bugzilla.wikimedia.org/show_bug.cgi?id=4445 bug (index key too long). See my comments there. I've "reopened" this bug but apologise if this was not the correct course of action. Best wishes.
Comment 4 Aryeh Gregor (not reading bugmail, please e-mail directly) 2007-12-16 21:14:51 UTC
Not relevant, that's a separate issue.  Re-resolving.

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