planner, sessionvar: avoid sending same task id to TiFlash #23747
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| @@ -820,6 +826,18 @@ type SessionVars struct { | |||
| AllowFallbackToTiKV map[kv.StoreType]struct{} | |||
| } | |||
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| // AllocMPPTaskID allocates task id for mpp tasks. It will reset the task id if the query's | |||
| // startTs is different. | |||
| func (s *SessionVars) AllocMPPTaskID(startTS uint64) int64 { | |||
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need a mutex to avoid write conflicts?
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it's only required by one session. You can notice that every variable in SessionVars is vulnerable.
It's impossible that two transaction shared same timestamp. |
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/merge |
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/lgtm |
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/run-sqllogic-test-1 |
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/merge |
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Signed-off-by: ti-srebot <ti-srebot@pingcap.com>
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cherry pick to release-5.0 in PR #23935 |
What problem does this PR solve?
Issue Number: close pingcap/tiflash#1706
For queries in same txn, the task ids sent to TiFlash might be same. I will cause some errors with a very small probability.
What is changed and how it works?
What's Changed:
Like AllocColumnID, we add a AllocMPPTaskID function in SessionVars. If the start_ts varies, the task id will reset.
Check List
Tests
Release note