> Attached is a patch against current CVS that fixes both of the known
> problems with sequences: failure to flush XLOG after a transaction
Great! Thanks... and sorry for missing these cases year ago -:)
Vadim
---(end of broadcast)---
TIP 1: subsc
> But sequences should not be under transaction control. Can you
> safely rollback a sequence? No! The only way to ensure that would
...
> Placing a restriction on an application that says it must treat the values
> returned from a sequence as if they might not be committed is absurd.
Why? The
> > This isn't an issue for a SELECT nextval() standing on
> > its own AFAIK the result will not be transmitted to the
> > client until after the commit happens. But it would be
> > an issue for a select executed inside a transaction
> > block (begin/commit).
>
> The behavior of SELECT nextval()
"'Ben Grimm'" <[EMAIL PROTECTED]> writes:
> On Fri, 15 Mar 2002, Tom Lane wrote:
>> What's bug #3? I don't recall a third issue.
> The problem I was seeing before is that when the postmaster was shutdown
> properly, log_cnt in the sequence record was saved with whatever value it
> had at the t
On Fri, 15 Mar 2002, Tom Lane wrote:
> "'Ben Grimm'" <[EMAIL PROTECTED]> writes:
> > When these bugs are fixed there is still the issue of bug #3 that I
> > came across. The one that I work around by resetting log_cnt to 0 when a
> > backend initializes a sequence. It's this third bug that ma
Attached is a patch against current CVS that fixes both of the known
problems with sequences: failure to flush XLOG after a transaction
that only does "SELECT nextval()", and failure to force a new WAL
record to be written on the first nextval after a checkpoint.
(The latter uses Vadim's idea of l
"'Ben Grimm'" <[EMAIL PROTECTED]> writes:
> When these bugs are fixed there is still the issue of bug #3 that I
> came across. The one that I work around by resetting log_cnt to 0 when a
> backend initializes a sequence. It's this third bug that made the other
> two so apparent. Fixing them
On Fri, 15 Mar 2002, Vadim Mikheev wrote:
> > But sequences should not be under transaction control. Can you
> > safely rollback a sequence? No! The only way to ensure that would
> ...
> > Placing a restriction on an application that says it must treat the values
> > returned from a sequence a
On Thu, 14 Mar 2002, Mikheev, Vadim wrote:
> And it's not. But behaviour of application *must* be
> conditional on was transaction committed or not.
>
> What's the problem for application that need nextval() for
> external (out-of-database) purposes to use sequence values
> only after transactio
Ben Grimm <[EMAIL PROTECTED]> writes:
> The behavior of SELECT nextval() should not be conditional on being in or
> out of a transaction block.
Nonsense. The behavior of INSERT or UPDATE is "conditional" in exactly
the same way: you should not rely on the reported result until it's
committed.
On Thu, 14 Mar 2002, Tom Lane wrote:
>
> If you do a SELECT nextval() and then use the returned value externally
> *without waiting for a commit acknowledgement*, then I think you are
> risking trouble; there's no guarantee that the WAL record (if one is
> needed) has hit disk yet, and so a crash
"Tom Pfau" <[EMAIL PROTECTED]> writes:
> I'm concerned that the discussion here has been of the opinion that
> since no records were written to the database using the value retrieved
> from the sequence that no damage has been done.
Um, you certainly didn't hear me saying that ;-)
There are two
On Thu, 14 Mar 2002, Tom Pfau wrote:
> I don't fully understand the xlog files or WAL records but...
>
> Why isn't the writing of the WAL record based on the CACHE value of the
> sequence? If a request to nextval() can't be satisfied by the cache,
> the sequence on disk should be updated result
I don't fully understand the xlog files or WAL records but...
Why isn't the writing of the WAL record based on the CACHE value of the
sequence? If a request to nextval() can't be satisfied by the cache,
the sequence on disk should be updated resulting in a WAL record being
written.
If two sessi
> > It seems safe to do NOT write WAL record if sequence
> > LSN > system RedoRecPtr because of checkpoint started after our
> > check would finish only after writing to disk sequence buffer with
> > proper last_value and log_cnt (nextval keeps lock on
> > sequence buffer).
>
> Mmm ... maybe. I
> AFAICS the only way that we could make the one-WAL-record-every-32-
> nextvals idea really work would be if CHECKPOINT could nullify the
> logged-in-advance state of each sequence (so that the first nextval
> after a checkpoint would always generate a fresh WAL record, but
> subsequent ones woul
I said:
> Mmm ... maybe. Is this safe if a checkpoint is currently in progress?
> Seems like you could look at RedoRecPtr and decide you are okay, but you
> really are not if checkpointer has already dumped sequence' disk
> buffer and will later set RedoRecPtr to a value beyond the old LSN.
Oh,
"Mikheev, Vadim" <[EMAIL PROTECTED]> writes:
> It seems safe to do NOT write WAL record if sequence
> LSN > system RedoRecPtr because of checkpoint started after our
> check would finish only after writing to disk sequence buffer with
> proper last_value and log_cnt (nextval keeps lock on sequence
18 matches
Mail list logo
