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https://issues.apache.org/jira/browse/SOLR-12684?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16591335#comment-16591335
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ASF subversion and git services commented on SOLR-12684:
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Commit bdaa9e8f560067d07a925220cbc7f1d2872a23dd in lucene-solr's branch
refs/heads/branch_7x from [~varunthacker]
[ https://git-wip-us.apache.org/repos/asf?p=lucene-solr.git;h=bdaa9e8 ]
SOLR-12684: Document speed gotchas and partitionKeys usage for ParallelStream.
Standardize search streams to specify the export handler in the examples for
expressions that operate on all the tuples
(cherry picked from commit fc9aac1)
> Document speed gotchas and partitionKeys usage for ParallelStream
> -----------------------------------------------------------------
>
> Key: SOLR-12684
> URL: https://issues.apache.org/jira/browse/SOLR-12684
> Project: Solr
> Issue Type: Bug
> Security Level: Public(Default Security Level. Issues are Public)
> Reporter: Varun Thacker
> Assignee: Varun Thacker
> Priority: Major
> Fix For: master (8.0), 7.5
>
> Attachments: SOLR-12684.patch, SOLR-12684.patch, SOLR-12684.patch,
> SOLR-12684.patch
>
>
> The aim of this Jira is to beef up the ref guide around parallel stream
> There are two things I want to address:
>
> Firstly usage of partitionKeys :
> This line in the ref guide indicates that parallel stream keys should always
> be the same as the underlying sort criteria
> {code:java}
> The parallel function maintains the sort order of the tuples returned by the
> worker nodes, so the sort criteria of the parallel function must match up
> with the sort order of the tuples returned by the workers.
> {code}
> But as discussed on SOLR-12635 , Joel provided an example
> {code:java}
> The hash partitioner just needs to send documents to the same worker node.
> You could do that with just one partitioning key
> For example if you sort on year, month and day. You could partition on year
> only and still be fine as long as there was enough different years to spread
> the records around the worker nodes.{code}
> So we should make this more clear in the ref guide.
> Let's also document that specifying more than 4 partitionKeys will throw an
> error after SOLR-12683
>
> At this point the user will understand how to use partitonKeys . It's related
> to the sort criteria but should not have all the sort fields
>
> We should now mention a trick where the user could warn up the hash queries
> as they are always run on the whole document set ( irrespective of the filter
> criterias )
> also users should only use parallel when the docs matching post filter
> criterias is very large .
> {code:java}
> <listener event="newSearcher" class="solr.QuerySenderListener">
> <arr name="queries">
> <lst><str name="q">:</str><str name="fq">{!hash workers=6 worker=0}</str><str
> name="partitionKeys">myPartitionKey</str></lst>
> <lst><str name="q">:</str><str name="fq">{!hash workers=6 worker=1}</str><str
> name="partitionKeys">myPartitionKey</str></lst>
> <lst><str name="q">:</str><str name="fq">{!hash workers=6 worker=2}</str><str
> name="partitionKeys">myPartitionKey</str></lst>
> <lst><str name="q">:</str><str name="fq">{!hash workers=6 worker=3}</str><str
> name="partitionKeys">myPartitionKey</str></lst>
> <lst><str name="q">:</str><str name="fq">{!hash workers=6 worker=4}</str><str
> name="partitionKeys">myPartitionKey</str></lst>
> <lst><str name="q">:</str><str name="fq">{!hash workers=6 worker=5}</str><str
> name="partitionKeys">myPartitionKey</str></lst>
> </arr>
> </listener>{code}
>
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