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https://issues.apache.org/jira/browse/DRILL-7187?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16829620#comment-16829620
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ASF GitHub Bot commented on DRILL-7187:
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amansinha100 commented on pull request #1772: DRILL-7187: Improve selectivity
estimation of BETWEEN predicates and …
URL: https://github.com/apache/drill/pull/1772
…arbitrary combination of range predicates.
- Also, propagate the totalRowCount to the histogram selectivity estimation
and use it instead of the nonNullCount.
- Before and after estimates for the following predicate:
`where o.o_orderdate >= date '1996-10-01' and o.o_orderdate < date
'1996-10-01' + interval '3' month`
BEFORE this PR: estimated filter row count = **3206**
AFTER this PR: estimated filter row count = **601**
ACTUAL row count = **561**
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> Improve selectivity estimates for range predicates when using histogram
> -----------------------------------------------------------------------
>
> Key: DRILL-7187
> URL: https://issues.apache.org/jira/browse/DRILL-7187
> Project: Apache Drill
> Issue Type: Bug
> Reporter: Aman Sinha
> Assignee: Aman Sinha
> Priority: Major
> Fix For: 1.17.0
>
>
> 2 types of selectivity estimation improvements need to be done:
> 1. For range predicates on the same column, we need to collect all such
> predicates in 1 group and do a histogram lookup for them together.
> For instance:
> {noformat}
> WHERE a > 10 AND b < 20 AND c = 100 AND a <= 50 AND b < 50
> {noformat}
> Currently, the Drill behavior is to treat each of the conjuncts
> independently and multiply the individual selectivities. However, that will
> not give the accurate estimates. Here, we want to group the predicates on 'a'
> together and do a single lookup. Similarly for 'b'.
> 2. NULLs are not maintained by the histogram but when doing the selectivity
> calculations, the histogram should use the totalRowCount as the denominator
> rather than the non-null count.
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