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Posted to dev@pig.apache.org by "Thejas M Nair (JIRA)" <ji...@apache.org> on 2010/06/29 01:49:52 UTC
[jira] Assigned: (PIG-1473) Avoid serialization/deserialization
costs for PigStorage data - Use custom Map and Bag implementation
[ https://issues.apache.org/jira/browse/PIG-1473?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Thejas M Nair reassigned PIG-1473:
----------------------------------
Assignee: Thejas M Nair
> Avoid serialization/deserialization costs for PigStorage data - Use custom Map and Bag implementation
> -----------------------------------------------------------------------------------------------------
>
> Key: PIG-1473
> URL: https://issues.apache.org/jira/browse/PIG-1473
> Project: Pig
> Issue Type: Improvement
> Affects Versions: 0.8.0
> Reporter: Thejas M Nair
> Assignee: Thejas M Nair
> Fix For: 0.8.0
>
>
> Cost of serialization/deserialization (sedes) can be very high and avoiding it will improve performance.
> Avoid sedes when possible by implementing approach #3 proposed in http://wiki.apache.org/pig/AvoidingSedes .
> The load function uses subclass of Map and DataBag which holds the serialized copy. LoadFunction delays deserialization of map and bag types until a member function of java.util.Map or DataBag is called.
> Example of query where this will help -
> {CODE}
> l = LOAD 'file1' AS (a : int, b : map [ ]);
> f = FOREACH l GENERATE udf1(a), b;
> fil = FILTER f BY $0 > 5;
> dump fil; -- Serialization of column b can be delayed until here using this approach .
> {CODE}
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