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From "Dmitriy V. Ryaboy (JIRA)" <j...@apache.org>
Subject [jira] Commented: (PIG-1473) Avoid serialization/deserialization costs for PigStorage data - Use custom Map and Bag implementation
Date Thu, 15 Jul 2010 22:20:50 GMT

    [ https://issues.apache.org/jira/browse/PIG-1473?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12888942#action_12888942
] 

Dmitriy V. Ryaboy commented on PIG-1473:
----------------------------------------

Thejas, do you think there could be any performance gains if we could delay deserialization
of the top-level fields in the tuple, but deserialize whole maps or databags if they are touched?

> 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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