On Tue, Feb 25, 2025 at 2:36 AM Amit Kapila <amit.kapil...@gmail.com> wrote: > > On Tue, Feb 25, 2025 at 1:03 AM Masahiko Sawada <sawada.m...@gmail.com> wrote: > > > > I've checked if this issue exists also on v15 or older, but IIUC it > > doesn't exist, fortunately. Here is the summary: > > > > Scenario-1: the source gets invalidated before the copy function > > fetches its contents for the first time. In this case, since the > > source slot's restart_lsn is already an invalid LSN it raises an error > > appropriately. In v15, we have only one slot invaldation reason, WAL > > removal, therefore we always reset the slot's restart_lsn to > > InvalidXlogRecPtr. > > > > Scenario-2: the source gets invalidated before the copied slot is > > created (i.e., between first content copy and > > create_logical/physical_replication_slot()). In this case, the copied > > slot could have a valid restart_lsn value that however might point to > > a WAL segment that might have already been removed. However, since > > copy_restart_lsn will be an invalid LSN (=0), it's caught by the > > following if condition: > > > > if (copy_restart_lsn < src_restart_lsn || > > src_islogical != copy_islogical || > > strcmp(copy_name, NameStr(*src_name)) != 0) > > ereport(ERROR, > > (errmsg("could not copy replication slot \"%s\"", > > NameStr(*src_name)), > > errdetail("The source replication slot was > > modified incompatibly during the copy operation."))); > > > > Scenario-3: the source gets invalidated after creating the copied slot > > (i.e. after create_logical/physical_replication_slot()). In this case, > > since the newly copied slot have the same restart_lsn as the source > > slot, both slots are invalidated. > > > > Which part of the code will cover Scenario-3? Shouldn't we give ERROR > for Scenario-3 as well?
In scenario-3, the backend process executing pg_copy_logical/physical_replication_slot() already holds the new copied slot and its restart_lsn is the same or older than the source slot's restart_lsn. Therefore, if the source slot is invalidated at that timing, the copied slot is invalidated too, resulting in an error by the backend. Regards, -- Masahiko Sawada Amazon Web Services: https://aws.amazon.com