[
https://issues.apache.org/jira/browse/SOLR-14923?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17213093#comment-17213093
]
David Smiley commented on SOLR-14923:
-------------------------------------
I am responsible for this bug, along with [~moshebla], the contributor of
SOLR-12638. Perhaps the single most bit of code I've regretted committing on
behalf of another are the few lines of code you have found Thomas. I expressed
my reservations at the time:
https://issues.apache.org/jira/browse/SOLR-12638?focusedCommentId=16872898&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-16872898
bq. What gnaws at me is that this "UpdateLog.openRealtimeSearcher" is being
called optimistically on a new doc because maaaayyyybeee some future atomic
update will need to see it. And not just any type of atomic update; one that is
directly to a nested child doc (something I consider highly experimental). It's
as if we're optimizing for making that future atomic update faster by doing
work in advance that will, I think, very rarely actually be used. It's a
tragedy, if I'm understanding this right.
There's a bit of conversation before in the issue about it as well. It's
difficult for me to say at the moment what the fix is because that's fairly
complex low-level Solr code that I think few people understand well.
Nonetheless I'll look into it further this week.
> Indexing performance is unacceptable when child documents are involved
> ----------------------------------------------------------------------
>
> Key: SOLR-14923
> URL: https://issues.apache.org/jira/browse/SOLR-14923
> Project: Solr
> Issue Type: Bug
> Security Level: Public(Default Security Level. Issues are Public)
> Components: update, UpdateRequestProcessors
> Affects Versions: master (9.0), 8.3, 8.4, 8.5, 8.6
> Reporter: Thomas Wöckinger
> Priority: Critical
> Labels: performance
>
> Parallel indexing does not make sense at moment when child documents are used.
> The org.apache.solr.update.processor.DistributedUpdateProcessor checks at the
> end of the method doVersionAdd if Ulog caches should be refreshed.
> This check will return true if any child document is included in the
> AddUpdateCommand.
> If so ulog.openRealtimeSearcher(); is called, this call is very expensive,
> and executed in a synchronized block of the UpdateLog instance, therefore all
> other operations on the UpdateLog are blocked too.
> Because every important UpdateLog method (add, delete, ...) is done using a
> synchronized block almost each operation is blocked.
> This reduces multi threaded index update to a single thread behavior.
> The described behavior is not depending on any option of the UpdateRequest,
> so it does not make any difference if 'waitFlush', 'waitSearcher' or
> 'softCommit' is true or false.
> The described behavior makes the usage of ChildDocuments useless, because the
> performance is unacceptable.
>
>
--
This message was sent by Atlassian Jira
(v8.3.4#803005)
---------------------------------------------------------------------
To unsubscribe, e-mail: issues-unsubscr...@lucene.apache.org
For additional commands, e-mail: issues-h...@lucene.apache.org
