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From "Namit Jain (JIRA)" <>
Subject [jira] [Commented] (HIVE-2845) Add support for index joins in Hive
Date Sun, 29 Jul 2012 14:46:35 GMT


Namit Jain commented on HIVE-2845:

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:
>             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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