ddl: improve compatibility for ALTER TABLE algorithms (#19270) #19364
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Signed-off-by: ti-srebot <ti-srebot@pingcap.com>
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/run-common-test --tidb-test=pr/1076 |
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LGTM |
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Aug 21, 2020
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cherry-pick #19270 to release-4.0
What problem does this PR solve?
Issue Number: close #19162
ALGORITHM=x means "this or better", whereby
INSTANT > INPLACE > COPY. As long the definition ofsupportedfield follows this order, the loop will always choose the best algorithm.The comparison works due to how types are defined in the parser. Its definition follows the order
default < copy < inplace < instant.So this loop means that if there is an equal or better algorithm, it is chosen. Maybe I should have a
LessOrEqualmethod on this type, and not to rely on the enum definition.If the chosen algorithm is not same as the specified one, an error is returned for TiDB to report the warning. So an error may come from the better algorithm choosing strategy, which is actually a successful case.
As a result, the fail case, no matching algorithm is identified by
AlgorithmTypeDefaultand an error.Check List
Tests
Release note