[
https://issues.apache.org/jira/browse/HIVE-17308?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16174202#comment-16174202
]
Lefty Leverenz commented on HIVE-17308:
---------------------------------------
Doc note: This changes the default value of
*hive.stats.correlated.multi.key.joins* to true.
No TODOC3.0 label is needed because it will be documented for HIVE-16298, which
created *hive.stats.correlated.multi.key.joins* in the same release (3.0.0).
> Improvement in join cardinality estimation
> ------------------------------------------
>
> Key: HIVE-17308
> URL: https://issues.apache.org/jira/browse/HIVE-17308
> Project: Hive
> Issue Type: Improvement
> Components: Query Planning
> Reporter: Vineet Garg
> Assignee: Vineet Garg
> Attachments: HIVE-17308.1.patch, HIVE-17308.2.patch,
> HIVE-17308.3.patch, HIVE-17308.4.patch, HIVE-17308.5.patch,
> HIVE-17308.6.patch, HIVE-17308.7.patch, HIVE-17308.8.patch
>
>
> Currently during logical planning join cardinality is estimated assuming no
> correlation among join keys (This estimation is done using exponential
> backoff). Physical planning on the other hand consider correlation for multi
> keys and uses different estimation. We should consider correlation during
> logical planning as well.
--
This message was sent by Atlassian JIRA
(v6.4.14#64029)
