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https://issues.apache.org/jira/browse/PIG-758?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Gunther Hagleitner updated PIG-758:
-----------------------------------
Description:
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.
was:
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:
{code}
a = load 'table' using DBLoader();
{code}
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:
{code}
a = load 'sql://table' using DBLoader();
{code}
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.
> 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
>
> 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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