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https://issues.apache.org/jira/browse/DRILL-1328?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15289403#comment-15289403
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ASF GitHub Bot commented on DRILL-1328:
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Github user vkorukanti commented on the pull request:
https://github.com/apache/drill/pull/425#issuecomment-220101853
Tested with parquet metadata cache. Currently if you do a count(*) on
parquet table having metadata cache, we get that count from cache. For rowcount
in planning: if a stats table exists we get the count from stats table,
otherwise we get it from groupscan which in parquet case gets it from the
metadata cache if exists.
> Support table statistics
> ------------------------
>
> Key: DRILL-1328
> URL: https://issues.apache.org/jira/browse/DRILL-1328
> Project: Apache Drill
> Issue Type: Improvement
> Reporter: Cliff Buchanan
> Fix For: Future
>
> Attachments: 0001-PRE-Set-value-count-in-splitAndTransfer.patch
>
>
> This consists of several subtasks
> * implement operators to generate statistics
> * add "analyze table" support to parser/planner
> * create a metadata provider to allow statistics to be used by optiq in
> planning optimization
> * implement statistics functions
> Right now, the bulk of this functionality is implemented, but it hasn't been
> rigorously tested and needs to have some definite answers for some of the
> parts "around the edges" (how analyze table figures out where the table
> statistics are located, how a table "append" should work in a read only file
> system)
> Also, here are a few known caveats:
> * table statistics are collected by creating a sql query based on the string
> path of the table. This should probably be done with a Table reference.
> * Case sensitivity for column statistics is probably iffy
> * Math for combining two column NDVs into a joint NDV should be checked.
> * Schema changes aren't really being considered yet.
> * adding getDrillTable is probably unnecessary; it might be better to do
> getTable().unwrap(DrillTable.class)
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