Hello, Michael. > Isn't the issue that we may select as arbiter indexes stuff that's !indisvalid? As far as I can see (1) !indisvalid indexes are filtered out.
But... It looks like this choice is not locked in any way (2), so index_concurrently_swap or index_concurrently_set_dead can change this index after the decision is made, even despite WaitForLockersMultiple (3). In some cases, it may cause a data loss... But I was unable to reproduce that using some random usleep(), however - maybe it is a wrong assumption. [1]: https://github.com/postgres/postgres/blob/915de706d28c433283e9dc63701e8f978488a2b9/src/backend/optimizer/util/plancat.c#L804 [2]: https://github.com/postgres/postgres/blob/915de706d28c433283e9dc63701e8f978488a2b9/src/backend/optimizer/util/plancat.c#L924-L928 [3]: https://github.com/postgres/postgres/blob/8aee330af55d8a759b2b73f5a771d9d34a7b887f/src/backend/commands/indexcmds.c#L4153
