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https://issues.apache.org/jira/browse/PIG-3642?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Lorand Bendig updated PIG-3642:
-------------------------------
Attachment: PIG-3642-5.patch
[~cheolsoo], the patch is rebased, minor adjustments were needed.
Only a few e2e tests are affected, so I turned off fetch at these
individually through the 'java_params' property. (It seems to
me that setting opt.fetch=false in testpropertiesfile.conf doesn't work)
> Direct HDFS access for small jobs (fetch)
> ------------------------------------------
>
> Key: PIG-3642
> URL: https://issues.apache.org/jira/browse/PIG-3642
> Project: Pig
> Issue Type: Improvement
> Reporter: Lorand Bendig
> Assignee: Lorand Bendig
> Fix For: 0.13.0
>
> Attachments: PIG-3642-3.patch, PIG-3642-4.patch, PIG-3642-5.patch,
> PIG-3642.patch
>
>
> With this patch I'd like to add the possibility to directly read data from
> HDFS instead of launching MR jobs in case of simple (map-only) tasks. Hive
> already has this feature (fetch). This patch shares some similarities with
> the local mode of Pig 0.6. Here, fetching kicks off when the following holds
> for a script:
> * it contains only LIMIT, FILTER, UNION (if no split is generated), STREAM,
> (nested) FOREACH with expression operators, custom UDFs..etc
> * no scalar aliases
> * no SampleLoader
> * single leaf job
> * DUMP (no STORE)
> The feature is enabled by default and can be toggled with:
> * -N or -no_fetch
> * set opt.fetch true/false;
> There's no STORE support because I wanted to make it explicit that this
> "optimization" is for launching small/simple scripts during development,
> rather than querying and filtering large number of rows on the client
> machine. However, a threshold could be given on the input size (an
> estimation) to determine whether to prefer fetch over MR jobs, similar to
> what Hive's '{{hive.fetch.task.conversion.threshold}}' does. (through Pig's
> LoadMetadata#getStatistic ?)
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