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https://issues.apache.org/jira/browse/DRILL-1328?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16061374#comment-16061374
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Gautam Kumar Parai commented on DRILL-1328:
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Based on the last discussion with the reviewers and Drill community members, we
would hold off on the PR because it also causes regressions in queries in
TPC-H, TPC-DS benchmarks. We identified that we need histograms and other
enhancements to fully address the regressions. I would post a new PR once these
issues are addressed.
> Support table statistics
> ------------------------
>
> Key: DRILL-1328
> URL: https://issues.apache.org/jira/browse/DRILL-1328
> Project: Apache Drill
> Issue Type: Improvement
> Reporter: Cliff Buchanan
> Assignee: Gautam Kumar Parai
> 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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