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https://issues.apache.org/jira/browse/SOLR-14518?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17118761#comment-17118761
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Joel Bernstein edited comment on SOLR-14518 at 5/28/20, 2:41 PM:
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I have a theory as to why the collapse approach was just as fast as the block
join approach in my testing. I was using the same block indexing for groups for
both queries.
So the collapse would have benefited from having all group records blocked
together because the same memory locations would have been accessed repeatedly
for each group member. For example the same array slot and doc values ordinal
lookups would have happened for the entire group. This would have decreased
memory bandwidth needed to collapse. So block indexing likely helps collapse as
much as it helps the parent block join or more because blockjoin has to track
back to find the group head and collapse doesn't have that backtracking
mechanism.
was (Author: joel.bernstein):
I have a theory as to why the collapse approach was just as fast as the block
join approach in my testing. I was using the same block indexing for groups for
both queries.
So the collapse would have benefited from the having the all group records
blocked together because the same memory locations would have been accessed
repeatedly for each group member. For example the same array slot and doc
values ordinal lookups would have happened for the entire group. This would
have decreased memory bandwidth needed to collapse. So block indexing likely
helps collapse as much as it helps the parent block join or more because
blockjoin has to track back to find the group head and collapse doesn't have
that backtracking mechanism.
> Add support for partitioned unique agg to JSON facets
> -----------------------------------------------------
>
> Key: SOLR-14518
> URL: https://issues.apache.org/jira/browse/SOLR-14518
> Project: Solr
> Issue Type: New Feature
> Components: Facet Module
> Reporter: Joel Bernstein
> Priority: Major
>
> There are scenarios where documents are partitioned across shards based on
> the same field that the *unique* agg is applied to with JSON facets. In this
> scenario exact unique counts can be calculated by simply sending the bucket
> level unique counts to the aggregator where they can be summed. Suggested
> syntax is to add a boolean flag to the unique aggregation function:
> *unique*(partitioned_field, true).
> The *true* value turns on the "partitioned" unique logic. The default is
> false.
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