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Posted to issues@hive.apache.org by "Jesus Camacho Rodriguez (JIRA)" <ji...@apache.org> on 2015/09/25 00:37:04 UTC
[jira] [Updated] (HIVE-11954) Extend logic to choose side table in
MapJoin Conversion algorithm
[ https://issues.apache.org/jira/browse/HIVE-11954?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Jesus Camacho Rodriguez updated HIVE-11954:
-------------------------------------------
Attachment: HIVE-11954.patch
> Extend logic to choose side table in MapJoin Conversion algorithm
> -----------------------------------------------------------------
>
> Key: HIVE-11954
> URL: https://issues.apache.org/jira/browse/HIVE-11954
> Project: Hive
> Issue Type: Bug
> Components: Physical Optimizer
> Affects Versions: 2.0.0
> Reporter: Jesus Camacho Rodriguez
> Assignee: Jesus Camacho Rodriguez
> Attachments: 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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