Daniel Dai commented on PIG-895:

Patch committed

> Default parallel for Pig
> ------------------------
>                 Key: PIG-895
>                 URL: https://issues.apache.org/jira/browse/PIG-895
>             Project: Pig
>          Issue Type: New Feature
>          Components: impl
>    Affects Versions: 0.3.0
>            Reporter: Daniel Dai
>             Fix For: 0.4.0
>         Attachments: PIG-895-1.patch, PIG-895-2.patch, PIG-895-3.patch
> For hadoop 20, if user don't specify the number of reducers, hadoop will use 
> 1 reducer as the default value. It is different from previous of hadoop, in 
> which default reducer number is usually good. 1 reducer is not what user want 
> for sure. Although user can use "parallel" keyword to specify number of 
> reducers for each statement, it is wordy. We need a convenient way for users 
> to express a desired number of reducers. Here is my propose:
> 1. Add one property "default_parallel" to Pig. User can set default_parallel 
> in script. Eg:
>    set default_parallel 10;
> 2. default_parallel is a hint to Pig. Pig is free to optimize the number of 
> reducers (unlike parallel keyword). Currently, since we do not have a 
> mechanism to determine the optimal number of reducers, default_parallel will 
> be always granted, unless it is override by "parallel" keyword.
> 3. If user put multiple default_parallel inside script, the last entry will 
> be taken.

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