Add "START TRANSACTION WITH CAUSAL CONSISTENCY ONLY" #1162
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Signed-off-by: ekexium <[email protected]>
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if external consistency (> strict serializability) is the default and is here considered orthogonal to RU/RC/RR stuff, what happens if i do START TRANSACTION /* WITH EXTERNAL CONSISTENCY */;
SET TRANSACTION ISOLATION LEVEL READ COMMITTED;
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@kennytm External consistency doesn't mean strict serializability. It is orthogonal to isolation levels. So I think it should not interfere with Read Committed. TiDB used to guarantee external consistency. The new feature async commit can break it (for better performance), so we need a new grammar to control the behavior. |
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@kennytm Right... External consistency can be an ambiguous word. |
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So to clarify, is "external consistency" here the same concept as the one mentioned in https://cloud.google.com/spanner/docs/true-time-external-consistency and https://stackoverflow.com/questions/60365103/differences-between-strict-serializable-and-external-consistency (which both claimed it is stronger than linearizability + serializability) |
No, the "external consistency" here is roughly the same with linearizability. It has nothing to do with serializability. |
Signed-off-by: ekexium <[email protected]>
…kexium/parser into add-start-without-external-consistency
Signed-off-by: ekexium <[email protected]>
Signed-off-by: ekexium <[email protected]>
kennytm
changed the title
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/lgtm |
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/merge |
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/run-all-tests |
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@ekexium merge failed. |
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/merge |
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/run-all-tests |
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@ekexium merge failed. |
* add a start transaction without external consistency statement Signed-off-by: ekexium <[email protected]> * change the grammar to 'with causal consistency' Signed-off-by: ekexium <[email protected]> * rename WithoutExternalConsistency to CausalConsistency Signed-off-by: ekexium <[email protected]> * change syntax to 'start transaction with causal consistency only' Signed-off-by: ekexium <[email protected]> Co-authored-by: ti-srebot <[email protected]>
Signed-off-by: ekexium [email protected]
What problem does this PR solve?
See pingcap/tidb#22597
What is changed and how it works?
Check List
Tests
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