planner: ban tiflash engine when the statement is not read only (#18458) #18534
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Signed-off-by: ti-srebot <ti-srebot@pingcap.com>
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Jul 15, 2020
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cherry-pick #18458 to release-4.0
What problem does this PR solve?
Issue Number: close #17851
Problem Summary: When the SQL is like
select *** for update. It's a not-read-only statement. The TiFlash plan changes the point get to point range table scan. But the lock operator has different performance between coprocessor and point get. So this causes the wrong results whenselect *** for updateby using the TiFlash. We decide to ban the TiFlash engine for a not-read-only statement.What is changed and how it works?
What's Changed: ban TiFlash engine for a not-read-only statement.
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