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https://issues.apache.org/jira/browse/PIG-3642?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13860531#comment-13860531
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Alan Gates commented on PIG-3642:
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I don't think this will result in the same local mode/mr mode problem that we
had before. The issue there was we tried (and failed) to have two modes where
Pig provided all features. This is much more limited to doing things locally
that can easily be done locally.
> 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.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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