[jira] Resolved: (PIG-1473) Avoid serialization/deserialization costs for PigStorage data - Use custom Map and Bag implementation

["Thejas M Nair (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/PIG-1473?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Thejas M Nair resolved PIG-1473.
--------------------------------

    Resolution: Won't Fix

Implementing lazy de-serialization using this approach will introduce a non backward compatible change in PigStorage . So closing this jira as wontfix. 

In PigStorage, if the de-serialization fails, the value is treated as null, ie tuple.get(i) returns null .
But if the de-serialization is delayed by returning a subclass of map or bag that holds the serialized data, the tuple.get(i) call will return a non null value even if the serialized format has a problem.

Though this approach is not being implemented in PigStorage() for this reason, other load store functions can potentially adopt this method.




> 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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