GitHub user Ben-Zvi reopened a pull request:
https://github.com/apache/drill/pull/765
DRILL-5293: Change the seed of the hash function for distribution
The fix is to use a different _seed_ for the hash function in the cases the
hash is computed for distribution (i.e., when calling the method
`getHashExpression(List<DistributionField> fields, RelDataType rowType)` ).
The implementation -- added a third parameter _seed_ to createCall() (on
line 102 in HashPrelUtil.java), which makes it use the "with seed" versions of
the generated code functions (before that it was using the versions that had a
built-in seed of zero).
Then made all the calling places pass in a seed -- zero in the case of a
Hash Table , or a large fixed prime ( 1301011 ) for distribution.
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/Ben-Zvi/drill DRILL-5293
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/drill/pull/765.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 #765
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commit de2ba4c0dc31c2c1f36be4ea220986d7e8eedc88
Author: Boaz Ben-Zvi <[email protected]>
Date: 2017-02-25T00:48:42Z
DRILL-5293: Change seed for distribution hash function to differ from that
of the hash table
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