Alan Gates reassigned PIG-58:

    Assignee: Olga Natkovich

> parameterized Pig scripts
> -------------------------
>                 Key: PIG-58
>                 URL: https://issues.apache.org/jira/browse/PIG-58
>             Project: Pig
>          Issue Type: New Feature
>            Reporter: Olga Natkovich
>            Assignee: Olga Natkovich
>             Fix For: 0.1.0
>         Attachments: PIG-58_v1.patch, PIG-58_v2, PIG-58_v3.patch
> This feature has been requested by several users and would be very useful in 
> conjunction with streaming. The feature would allow pig script to include 
> parameters that are replaced at run time. For instance, if your script needs 
> to run on a daily basis over the data of the previous day, you would be able 
> to use the script and providing a date as a run-time parameter to it.
> Example:
> =======
> Pig script myscript.pig:
> A = load '/data/mydata/%date%';
> B = filter A by $0>'5';
> .....
> Pig command line:
> pig -param date='20080110' myscript.pig
> Proposed interface and implementation:
> Interface:
> =======
> (0) Substitution will be only supported with pig script files.
> (1) Parameters are specified on the command line via -param <param>=<val> 
> construct. Multiple parameters can be specified. They are applied to the 
> script in the order they are specified on the command line
> (2) Default values for the parameters can be specified within the script via 
> decare statement:
> decare <param>=<value>
> (3) Withint the script the parameter will be enclosed in %%. \% can be used 
> te escape.
> Implementation:
> ============
> Use preprocessor to do the substitution. The preprocessor would be invoced by 
> Main before grunt is instanciated and do the following:
> - create a new file in temp location
> - build a hash of parameters from command line and declare statement
> - for each line in the original script
>   if this is a declare line, skip it
>   else for each unescaped pattern %<identifie>% look for a match in the hash. 
> Replace, if found.  Write the line to the temp file.
> - pass the temp file to grunt.

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