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https://issues.apache.org/jira/browse/HIVE-2845?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13424559#comment-13424559
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Namit Jain commented on HIVE-2845:
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Say there is a index of table A on 'key'.
For a query of the type:
select .. from A join B on A.key=B.key;
the plan can be as follows:
scan B
for every row of B (or a batch of rows in B), lookup the value using the index
in A
The basic infra-structure is needed first. A lot of optimizations can be added
later.
> Add support for index joins in Hive
> -----------------------------------
>
> Key: HIVE-2845
> URL: https://issues.apache.org/jira/browse/HIVE-2845
> Project: Hive
> Issue Type: New Feature
> Components: Indexing, Query Processor
> Reporter: Namit Jain
> Labels: indexing, joins, performance
>
> Hive supports indexes, which are used for filters currently.
> It would be very useful to add support for index-based joins in Hive.
> If 2 tables A and B are being joined, and an index exists on the join key of
> A,
> B can be scanned (by the mappers), and for each row in B, a lookup for the
> corresponding row in A can be performed.
> This can be very useful for some usecases.
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