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From jianqiao <...@git.apache.org>
Subject [GitHub] incubator-quickstep pull request #106: Improve StarSchemaSimpleCostModel to ...
Date Tue, 04 Oct 2016 22:22:48 GMT
GitHub user jianqiao opened a pull request:


    Improve StarSchemaSimpleCostModel to provide better group cardinality estimation for aggregations.

    This PR revises `StarSchemaSimpleCostModel` to provide better group cardinality estimation
for aggregations. This information will be used by a subsequent PR from Harshad to decide
when to use _partitioned hash tables_.
    The estimation relies on the _number of distinct values_ statistic of each group-by attribute,
which can be gathered by running `\analyze` command on the corresponding table.
    This PR does not affect the query plans for SSB queries. It changes some of the TPC-H
query plans (and a subsequent `LIPFilter` PR will bring more changes to TPC-H query plans).

You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/apache/incubator-quickstep estimate-num-distinct-values

Alternatively you can review and apply these changes as the patch at:


To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #106
commit ad1f8c406954778d332f02b680e08e0118727436
Author: Jianqiao Zhu <jianqiao@cs.wisc.edu>
Date:   2016-10-04T04:58:30Z

    Improve StarSchemaSimpleCostModel to provide closer estimation of number of groups for
hash aggregation.


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