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https://issues.apache.org/jira/browse/DRILL-3759?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15138971#comment-15138971
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John Omernik commented on DRILL-3759:
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I am tossing my +1 on this JIRA any sort of larger tables in Parquet, where you
are running accross multiple subdirectories (consider a years worth of data)
with multiple files (even say 25 files per day) would result is excessive query
planning do to the parser reviewing all files. Even when a prune operation is
requested by the user, causing a very poor user experience on these tables.
> Make partition pruning multi-phased to reduce the working set kept in memory
> ----------------------------------------------------------------------------
>
> Key: DRILL-3759
> URL: https://issues.apache.org/jira/browse/DRILL-3759
> Project: Apache Drill
> Issue Type: Improvement
> Components: Query Planning & Optimization
> Affects Versions: 1.1.0
> Reporter: Aman Sinha
> Assignee: Mehant Baid
> Fix For: Future
>
>
> Currently, partition pruning gets all file names in the table and applies the
> pruning. Suppose the files are spread out over several directories and there
> is a filter on dirN, this is not efficient - both in terms of elapsed time
> and memory usage. This has been seen in a few use cases recently.
> Wherever possible, we should ideally perform the pruning in N steps (where N
> is the number of directory levels referenced in the filter conditions):
> 1. Get the directory and filenames at level i
> 2. Materialize into the in-memory table
> 3. Apply interpreter-based evaluation of filter condition
> 4. Determine qualifying directories, increment i and repeat from step 1
>
> This multi phase approach may not be possible for certain types of filters -
> e,g for disjunctions. This analysis needs to be done.
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