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From "Hong Tang (JIRA)" <j...@apache.org>
Subject [jira] Commented: (PIG-879) Pig should provide a way for input location string in load statement to be passed as-is to the Loader
Date Fri, 10 Jul 2009 18:57:15 GMT

    [ https://issues.apache.org/jira/browse/PIG-879?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12729771#action_12729771
] 

Hong Tang commented on PIG-879:
-------------------------------

Both are valid arguments. The problem of 2) and 4) are that they require change to the load
statement syntax or load-func api and would take longer to get there. 

I guess we could structure the fix in two phases: Phase One: supporting 1) and 3), so that
we can have the minimum to move along without having to disable multi-query optimization completely.
User should be able to modify the script to change all relative paths to absolute ones (the
chance of such usage should be rare that most people should not be impacted). Phase Two: support
either 2) or 4) (but I do not think we need both). And personally I think 4) would be better
because loader should be the one that interprets the location string syntax.

> Pig should provide a way for input location string in load statement to be passed as-is
to the Loader
> -----------------------------------------------------------------------------------------------------
>
>                 Key: PIG-879
>                 URL: https://issues.apache.org/jira/browse/PIG-879
>             Project: Pig
>          Issue Type: Bug
>    Affects Versions: 0.3.0
>            Reporter: Pradeep Kamath
>
>  Due to multiquery optimization, Pig always converts the filenames to absolute URIs (see
http://wiki.apache.org/pig/PigMultiQueryPerformanceSpecification - section about Incompatible
Changes - Path Names and Schemes). This is necessary since the script may have "cd .." statements
between load or store statements and if the load statements have relative paths, we would
need to convert to absolute paths to know where to load/store from. To do this QueryParser.massageFilename()
has the code below[1] which basically gives the fully qualified hdfs path
>  
> However the issue with this approach is that if the filename string is something like
"hdfs://localhost.localdomain:39125/user/bla/1,hdfs://localhost.localdomain:39125/user/bla/2",
the code below[1] actually translates this to hdfs://localhost.localdomain:38264/user/bla/1,hdfs://localhost.localdomain:38264/user/bla/2
and throws an exception that it is an incorrect path.
>  
> Some loaders may want to interpret the filenames (the input location string in the load
statement) in any way they wish and may want Pig to not make absolute paths out of them.
>  
> There are a few options to address this:
> 1)    A command line switch to indicate to Pig that pathnames in the script are all absolute
and hence Pig should not alter them and pass them as-is to Loaders and Storers. 
> 2)    A keyword in the load and store statements to indicate the same intent to pig
> 3)    A property which users can supply on cmdline or in pig.properties to indicate the
same intent.
> 4)    A method in LoadFunc - relativeToAbsolutePath(String filename, String curDir) which
does the conversion to absolute - this way Loader can chose to implement it as a noop.
> Thoughts?
>  

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