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https://issues.apache.org/jira/browse/DRILL-2743?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14697764#comment-14697764
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ASF GitHub Bot commented on DRILL-2743:
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GitHub user StevenMPhillips opened a pull request:
https://github.com/apache/drill/pull/114
DRILL-2743: Parquet file metadata caching
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/StevenMPhillips/incubator-drill meta2
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/drill/pull/114.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #114
----
commit 371153d7dfb4cd0ad5b0042f6ca2df255e81c52f
Author: Steven Phillips <[email protected]>
Date: 2015-03-13T23:12:34Z
DRILL-2743: Parquet file metadata caching
----
> Parquet file metadata caching
> -----------------------------
>
> Key: DRILL-2743
> URL: https://issues.apache.org/jira/browse/DRILL-2743
> Project: Apache Drill
> Issue Type: New Feature
> Components: Storage - Parquet
> Reporter: Steven Phillips
> Assignee: Steven Phillips
> Fix For: 1.3.0
>
> Attachments: DRILL-2743.patch, drill.parquet_metadata
>
>
> To run a query against parquet files, we have to first recursively search the
> directory tree for all of the files, get the block locations for each file,
> and read the footer from each file, and this is done during the planning
> phase. When there are many files, this can result in a very large delay in
> running the query, and it does not scale.
> However, there isn't really any need to read the footers during planning, if
> we instead treat each parquet file as a single work unit, all we need to know
> are the block locations for the file, the number of rows, and the columns. We
> should store only the information which we need for planning in a file
> located in the top directory for a given parquet table, and then we can delay
> reading of the footers until execution time, which can be done in parallel.
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