Re: Snapshot warning

Tom Lane escribió:
> Alvaro Herrera <alvherre(at)commandprompt(dot)com> writes:
> > Tom Lane escribió:
> >> I think the fundamental bug here is that you tried to skip using the
> >> ResourceOwner mechanism for snapshot references. That's basically
> >> not gonna work.
>
> > Right :-( I'll see how to go about this.
>
> It strikes me that you might be able to remove the registered-snapshot
> infrastructure in snapmgr.c, and end up with about the same amount of
> code overall, just with the responsibility in resowner.c.

Seems to work, and fixes Pavan test case as well.

$ runpg 00head showdiff | diffstat
backend/utils/resowner/resowner.c | 99 ++++++++++++++++++++
backend/utils/time/snapmgr.c | 180 ++++++-------------!!!!!!!!!!!!!!!!!
include/utils/resowner.h | 8 +
include/utils/snapmgr.h | 3
4 files changed, 143 insertions(+), 59 deletions(-), 88 modifications(!)

I need to fix some comments before publishing the patch.

The only thing I'm now missing is SnapshotResetXmin(). It currently
looks like this:

static void
SnapshotResetXmin(void)
{
if (RegisteredSnapshotList == NULL && ActiveSnapshot == NULL)
MyProc->xmin = InvalidTransactionId;
}

After the patch we don't have any way to detect whether resowner.c has
any snapshot still linked to. I assume there's no objection to adding a
new entry point in resowner.c for this.

--
Alvaro Herrera http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.