Fix forever hanging when HashAgg is called by apply #12760
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@@ Coverage Diff @@
## master #12760 +/- ##
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Coverage 79.9575% 79.9575%
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Files 462 462
Lines 105416 105416
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Hits 84288 84288
Misses 14902 14902
Partials 6226 6226 |
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What problem does this PR solve?
Fix #12759
What is changed and how it works?
The parent executors(apply) of HashAgg may call
HashAgg.Nextonce more to make sure the returned size of chunk is 0.HashAgg.Nexthandle these calls incorrectly after its allfinalWorksexits.On each call of
HashAgg.Nextafter the job done, it returns a chunk with 0 size, but put a chk intofinalInputCh. Each apply executor will call aHashAgg.Nextonce more, when the number of parent executors exceeds the channel buffer, the query will hang forever.Explain the example in #12759,
HashAgg.Nextwhich returns a one-row chunk to its parent, sends the chunk into the buffer (This is valid).HashAgg.Nextcalled by each of the three apply, which returns a zero-row chunk to its parent, sends the chunk into the buffer (This should not happen).HashAgg.Nextcalled by the session of tidb, which returns a zero-row chunk to its parent, sends the chunk into the buffer and hangs forever.Check List
Tests
Code changes
Side effects
Related changes
Release note