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https://issues.apache.org/jira/browse/DRILL-6825?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16673860#comment-16673860
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Boaz Ben-Zvi commented on DRILL-6825:
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We were talking a while back about changing the use of hash functions, instead
of generating code – make a virtual call that computes the hash value for each
type of vector (similar to the `copyEntry()` in the `ValueVector`).
And then compute the hash value by iterating over the key columns (similar to
`appendRow()` in `VectorContainer` - though need to know which columns belong
to the key).
Also this would remove the hash value computation from the HashTable.
Don't remember if a Jira was opened for that work. This would definitely
simplify using different hash functions, per each datatype.
One last point - may need to keep various integers hashing compatibility - so
best if `HashValue(X as smallIint) == HashValue(X as int) == HashValue(X as
bigint)`
> Applying different hash function according to data types and data size
> ----------------------------------------------------------------------
>
> Key: DRILL-6825
> URL: https://issues.apache.org/jira/browse/DRILL-6825
> Project: Apache Drill
> Issue Type: Improvement
> Components: Execution - Codegen
> Reporter: weijie.tong
> Priority: Major
> Fix For: 1.16.0
>
>
> Different hash functions have different performance according to different
> data types and data size. We should choose a right one to apply not just
> Murmurhash.
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