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From "Jesus Camacho Rodriguez (JIRA)" <>
Subject [jira] [Updated] (HIVE-11954) Extend logic to choose side table in MapJoin Conversion algorithm
Date Thu, 01 Oct 2015 08:57:27 GMT


Jesus Camacho Rodriguez updated HIVE-11954:
    Attachment: HIVE-11954.02.patch

> Extend logic to choose side table in MapJoin Conversion algorithm
> -----------------------------------------------------------------
>                 Key: HIVE-11954
>                 URL:
>             Project: Hive
>          Issue Type: Bug
>          Components: Physical Optimizer
>    Affects Versions: 2.0.0
>            Reporter: Jesus Camacho Rodriguez
>            Assignee: Jesus Camacho Rodriguez
>         Attachments: HIVE-11954.01.patch, HIVE-11954.02.patch, HIVE-11954.patch, HIVE-11954.patch
> Selection of side table (in memory/hash table) in MapJoin Conversion algorithm needs
to be more sophisticated.
> In an N way Map Join, Hive should pick an input stream as side table (in memory table)
that has least cost in producing relation (like TS(FIL|Proj)*).
> Cost based choice needs extended cost model; without return path its going to be hard
to do this.
> For the time being we could employ a modified cost based algorithm for side table selection.
> New algorithm is described below:
> 1. Identify the candidate set of inputs for side table (in memory/hash table) from the
inputs (based on conditional task size)
> 2. For each of the input identify its cost, memory requirement. Cost is 1 for each heavy
weight relation op (Join, GB, PTF/Windowing, TF, etc.). Cost for an input is the total no
of heavy weight ops in its branch.
> 3. Order set from #1 on cost & memory req (ascending order)
> 4. Pick the first element from #3 as the side table.

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