statistics: improve estimation for index equal condition (#17366) #17609
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Signed-off-by: sre-bot <sre-bot@pingcap.com>
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cherry-pick #17366 to release-3.0
What problem does this PR solve?
Issue Number: close #17364
Problem Summary:
Wrong plan is chosen when index equal condition contains value which is out of the range of the histogram.
What is changed and how it works?
What's Changed:
Compute the NDV for the prefix columns of the index which are used for equal condition, and use it for row count guess.
How it Works:
It is more reasonable than hard-coded constant
outOfRangeBetweenRate.Related changes
N/A
Check List
Tests
Side effects
N/A
Release note