| From: | Thomas Munro <thomas(dot)munro(at)gmail(dot)com> |
|---|---|
| To: | Dmitry Dolgov <9erthalion6(at)gmail(dot)com> |
| Cc: | artem(dot)anisimov(dot)255(at)gmail(dot)com, pgsql-bugs(at)lists(dot)postgresql(dot)org |
| Subject: | Re: BUG #17949: Adding an index introduces serialisation anomalies. |
| Date: | 2023-06-19 02:29:46 |
| Message-ID: | CA+hUKGKuETgQ5a+uS2grX+muz5zEqCD36vM0xDt_C+Utx761nw@mail.gmail.com |
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| Lists: | pgsql-bugs |
How is this schedule supposed to work?
S1: _bt_search(&buf)
S1: if (!BufferIsValid(buf)) // because index is empty
S1: {
S1: PredicateLockRelation(...);
S1: ...
S1: return false; // no tuples for you
S2: _bt_search(&buf)
S1: INSERT ...
S2: if (!BufferIsValid(buf)) // because index *was* empty
S2: {
S2: PredicateLockRelation(...);
S2: ...
S2: return false; // no tuples for you
S2: ...
My point is that S2 won't ever scan S1's tuples, so it won't pass S1's
xid to CheckForSerializableConflictOut(). Am I missing something? I
can repro this with NR_THREADS set to only 2, after inserting
pg_usleep(1) after the _bt_search() in _bt_first() (sched_yield()
wasn't quite enough).
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| Next Message | Thomas Munro | 2023-06-19 03:23:31 | Re: BUG #17949: Adding an index introduces serialisation anomalies. |
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