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From "Daniel Dai (JIRA)" <j...@apache.org>
Subject [jira] Closed: (PIG-758) Converting load/store locations into fully qualified absolute paths
Date Fri, 14 May 2010 06:46:58 GMT

     [ https://issues.apache.org/jira/browse/PIG-758?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Daniel Dai closed PIG-758.
--------------------------


> Converting load/store locations into fully qualified absolute paths
> -------------------------------------------------------------------
>
>                 Key: PIG-758
>                 URL: https://issues.apache.org/jira/browse/PIG-758
>             Project: Pig
>          Issue Type: Bug
>            Reporter: Gunther Hagleitner
>             Fix For: 0.7.0
>
>
> As part of the multiquery optimization work there is a need to use absolute paths for
load and store operations (because the current directory changes during the execution of the
script). In order to do so, we are suggesting a change to the semantics of the location/filename
string used in LoadFunc and Slicer/Slice.
> The proposed change is:
>    * Load locations without a scheme part are expected to be hdfs (mapreduce mode) or
local (local mode) paths
>    * Any hdfs or local path will be translated to a fully qualified absolute path before
it is handed to either a LoadFunc or Slicer
>    * Any scheme other than "file" or "hdfs" will result in the load path to be passed
through to the LoadFunc or Slicer without any modification.
> Example:
> If you have a LoadFunc that reads from a database, in the current system the following
could be used:
> {noformat}
> a = load 'table' using DBLoader();
> {noformat}
> With the proposed changes table would be translated into an hdfs path though ("hdfs://..../table").
Probably not what the DBLoader would want to see. In order to make it work one could use:
> {noformat}
> a = load 'sql://table' using DBLoader();
> {noformat}
> Now the DBLoader would see the unchanged string "sql://table".
> This is an incompatible change, but hopefully not affecting many existing Loaders/Slicers.
Since this is needed with the multiquery feature, the behavior can be reverted back by using
the "no_multiquery" pig flag.

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