DomainException / NullResult holds no constraint
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Description

Spotted in production:

DomainException: NullResult holds no constraint

Urls all seem of the same style, differing Q values

/w/api.php?action=wbcheckconstraints&format=json&uselang=en&id=Qxxxxx

Stacktrace:

#0 /srv/mediawiki/php-1.31.0-wmf.5/extensions/Wikidata/extensions/Constraints/includes/ConstraintCheck/DelegatingConstraintChecker.php(577): WikibaseQuality\ConstraintReport\ConstraintCheck\Result\NullResult->getConstraint()
#1 [internal function]: Closure$WikibaseQuality\ConstraintReport\ConstraintCheck\DelegatingConstraintChecker::sortResult(WikibaseQuality\ConstraintReport\ConstraintCheck\Result\CheckResult, WikibaseQuality\ConstraintReport\ConstraintCheck\Result\NullResult)
#2 /srv/mediawiki/php-1.31.0-wmf.5/extensions/Wikidata/extensions/Constraints/includes/ConstraintCheck/DelegatingConstraintChecker.php(595): uasort(array, Closure$WikibaseQuality\ConstraintReport\ConstraintCheck\DelegatingConstraintChecker::sortResult;2735)
#3 /srv/mediawiki/php-1.31.0-wmf.5/extensions/Wikidata/extensions/Constraints/includes/ConstraintCheck/DelegatingConstraintChecker.php(134): WikibaseQuality\ConstraintReport\ConstraintCheck\DelegatingConstraintChecker->sortResult(array)
#4 /srv/mediawiki/php-1.31.0-wmf.5/extensions/Wikidata/extensions/Constraints/api/CheckConstraints.php(235): WikibaseQuality\ConstraintReport\ConstraintCheck\DelegatingConstraintChecker->checkAgainstConstraintsOnEntityId(Wikibase\DataModel\Entity\ItemId, NULL, array)
#5 /srv/mediawiki/php-1.31.0-wmf.5/extensions/Wikidata/extensions/Constraints/api/CheckConstraints.php(214): WikibaseQuality\ConstraintReport\Api\CheckConstraints->checkItems(array, NULL)
#6 /srv/mediawiki/php-1.31.0-wmf.5/includes/api/ApiMain.php(1582): WikibaseQuality\ConstraintReport\Api\CheckConstraints->execute()
#7 /srv/mediawiki/php-1.31.0-wmf.5/includes/api/ApiMain.php(544): ApiMain->executeAction()
#8 /srv/mediawiki/php-1.31.0-wmf.5/includes/api/ApiMain.php(515): ApiMain->executeActionWithErrorHandling()
#9 /srv/mediawiki/php-1.31.0-wmf.5/api.php(94): ApiMain->execute()
#10 /srv/mediawiki/w/api.php(3): include(string)
#11 {main}

Details

Related Changes in Gerrit:

Subject	Repo	Branch	Lines +/-
Fix sorting of NullResults	mediawiki/extensions/WikibaseQualityConstraints	wmf/1.31.0-wmf.5	+29 -0
Fix sorting of NullResults	mediawiki/extensions/Wikidata	wmf/1.31.0-wmf.5	+29 -0
Fix sorting of NullResults	mediawiki/extensions/WikibaseQualityConstraints	master	+29 -0

Customize query in gerrit

Related Objects

Mentioned Here: T179156: 503 spikes and resulting API slowness starting 18:45 October 26

Event Timeline

• demon created this task.Oct 25 2017, 7:48 PM

Restricted Application added a subscriber: Aklapper. · View Herald TranscriptOct 25 2017, 7:48 PM

hoo assigned this task to Lucas_Werkmeister_WMDE.Oct 25 2017, 7:50 PM

Framawiki subscribed.Oct 25 2017, 9:24 PM

Lucas_Werkmeister_WMDE added projects: Wikidata-Former-Sprint-Board, Wikibase-Quality.Oct 26 2017, 9:42 AM

Lucas_Werkmeister_WMDE moved this task from Proposed to Doing on the Wikidata-Former-Sprint-Board board.

Ah, I didn’t think about that. Happens when you have two identical statements (same main snak hash) with a property that doesn’t have any constraints. We add a NullResult for each of them so they still appear in the API response, we try to sort all the results (including the NullResults), the snaks are identical so the comparer tries to compare the constraints, boom. Fix coming up.

Change 386597 had a related patch set uploaded (by Lucas Werkmeister (WMDE); owner: Lucas Werkmeister (WMDE)):
[mediawiki/extensions/WikibaseQualityConstraints@master] Fix sorting of NullResults

https://gerrit.wikimedia.org/r/386597

gerritbot added a project: Patch-For-Review.Oct 26 2017, 10:15 AM

Lucas_Werkmeister_WMDE moved this task from Doing to Review on the Wikidata-Former-Sprint-Board board.Oct 26 2017, 10:15 AM

One example item where this happens is Q37038369 (ApiSandbox), due to its two “source of energy: coal” statements. (Found with this query.)

Correction: this happens on any item with two identical statements, regardless of whether the property has constraints or not. (Another example: Denmark (Q35)’s head of government (P6).) So this is probably a lot more common than I first thought.

Change 386597 merged by jenkins-bot:
[mediawiki/extensions/WikibaseQualityConstraints@master] Fix sorting of NullResults

https://gerrit.wikimedia.org/r/386597

@Ladsgroup will backport during today’s Morning SWAT (18:00–19:00 UTC).

Change 386653 had a related patch set uploaded (by Ladsgroup; owner: Lucas Werkmeister (WMDE)):
[mediawiki/extensions/WikibaseQualityConstraints@wmf/1.31.0-wmf.5] Fix sorting of NullResults

https://gerrit.wikimedia.org/r/386653

Change 386654 had a related patch set uploaded (by Ladsgroup; owner: Amir Sarabadani):
[mediawiki/extensions/Wikidata@wmf/1.31.0-wmf.5] Fix sorting of NullResults

https://gerrit.wikimedia.org/r/386654

Change 386654 merged by jenkins-bot:
[mediawiki/extensions/Wikidata@wmf/1.31.0-wmf.5] Fix sorting of NullResults

https://gerrit.wikimedia.org/r/386654

Mentioned in SAL (#wikimedia-operations) [2017-10-26T18:51:20Z] <ladsgroup@tin> Synchronized php-1.31.0-wmf.5/extensions/Wikidata/extensions/Constraints/includes/ConstraintCheck/DelegatingConstraintChecker.php: Fix sorting of NullResults (T179038) (duration: 01m 04s)

Mentioned in SAL (#wikimedia-operations) [2017-10-26T18:52:45Z] <ladsgroup@tin> Synchronized php-1.31.0-wmf.5/extensions/Wikidata/extensions/Constraints/tests/phpunit/DelegatingConstraintCheckerTest.php: Fix sorting of NullResults (T179038) (duration: 00m 49s)

Change 386653 merged by jenkins-bot:
[mediawiki/extensions/WikibaseQualityConstraints@wmf/1.31.0-wmf.5] Fix sorting of NullResults

https://gerrit.wikimedia.org/r/386653

Seems to be fixed, thanks @Ladsgroup! Please reopen if there are any new log errors.

Lucas_Werkmeister_WMDE closed this task as Resolved.Oct 26 2017, 7:08 PM

Mentioned in SAL (#wikimedia-operations) [2017-10-26T19:12:24Z] <ladsgroup@tin> Synchronized php-1.31.0-wmf.5/extensions/WikibaseQualityConstraints/tests/phpunit/DelegatingConstraintCheckerTest.php: Fix sorting of NullResults (T179038) (duration: 00m 50s)

Mentioned in SAL (#wikimedia-operations) [2017-10-26T19:14:05Z] <ladsgroup@tin> Synchronized php-1.31.0-wmf.5/extensions/WikibaseQualityConstraints/includes/ConstraintCheck/DelegatingConstraintChecker.php: Fix sorting of NullResults (T179038) (duration: 00m 49s)

Note: the backport was reverted due to (hopefully) unrelated problems (T179156), but since we could already see that it fixed the problem during the short time it was deployed, I don’t think we need to reopen this task – we can just wait until either the backport or the regular commit is deployed.

ReleaseTaggerBot added a project: MW-1.31-release-notes (WMF-deploy-2017-10-31 (1.31.0-wmf.6)).Oct 30 2017, 4:01 PM

ReleaseTaggerBot edited projects, added: MW-1.31-release-notes (WMF-deploy-2017-10-24 (1.31.0-wmf.5)); removed: MW-1.31-release-notes (WMF-deploy-2017-10-31 (1.31.0-wmf.6)).Oct 30 2017, 5:01 PM

• mmodell changed the subtype of this task from "Task" to "Production Error".Aug 28 2019, 11:10 PM

DomainException / NullResult holds no constraintClosed, ResolvedPublicPRODUCTION ERRORActions

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DomainException / NullResult holds no constraint
Closed, ResolvedPublicPRODUCTION ERROR
Actions