> I'd guess some WAL record arising from the post-crash master restart makes
the
> standby do so. When a crash isn't involved, the commit or abort record is
>that
> signal. You could test and find out how it happens after a master crash with
>a
> procedure like this:
>
> 1. Start a master and standby on the same machine.
> 2. Connect to master; CREATE TABLE t(); BEGIN; ALTER TABLE t ADD c int;
> 3. kill -9 -`head -n1 $master_PGDATA/postmaster.pid`
> 4. Connect to standby and confirm that t is still locked.
> 5. Attach debugger to standby startup process and set breakpoints on
> StandbyReleaseLocks and StandbyReleaseLocksMany.
> 6. Restart master.
Well yes, based on the test the stack is something like:
StandbyReleaseLocksManyStandbyReleaseOldLocks
ProcArrayApplyRecoveryInfo
xlog_redo
It's not very clear to me what ProcArrayApplyRecoveryInfo does (not too
familiar with the standby part I guess) but I see it's called by xlog_redo in
the "info == XLOG_CHECKPOINT_SHUTDOWN" case and by StartupXLOG.
But I don't know if calling ResetUnloggedRelations before
the call to ProcArrayApplyRecoveryInfo in xlog_redo makes sense...
if it makes sense, it would solve the problem of the stray files in
the master crashing case I guess?
> > > When you promote the standby, though,
> > ShutdownRecoveryTransactionEnvironment()
> > > releases the locks.
If I understand the code, ResetUnloggedRelations is called before
ShutdownRecoveryTransactionEnvironment, so that part shouldn't be
an issue
Leonardo
