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https://issues.apache.org/jira/browse/PIG-895?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Daniel Dai updated PIG-895:
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Description:
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.
was:
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.
> 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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