tidb_query: fix analyze column inconsistent behavior betwen TiDB and TiKV (#6055) #6096
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Signed-off-by: Lonng <heng@lonng.org>
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cherry-pick #6055 to release-3.0
Signed-off-by: Lonng heng@lonng.org
What have you changed?
The TiKV has inconsistent behavior with TiDB about analyzing column. see:
https://github.com/pingcap/tidb/blob/eae41adc0cd4a617d792a8bb426033c433a70527/statistics/sample.go#L173
The TiDB assumes samples will keep order with the original data order if the samples count greater than the
max_sample_count. But TiKV replaces the original data if the index conflict, which breaks the assumption.According to the TiDB logic, we should remove the item which index conflected, and append the new item to the samples.
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