Re: Hot Standby 0.2.1

Simon Riggs wrote:
> On Mon, 2009-09-21 at 14:01 +0100, Simon Riggs wrote:
>> On Mon, 2009-09-21 at 13:50 +0300, Heikki Linnakangas wrote:
> 
>>> is this that we seem to be missing conflict
>>> resolution for GiST index tuples deleted by the kill_prior_tuples
>>> mechanism. Unless I'm missing something, we need similar handling there
>>> that we have in b-tree.
>> OK, I agree with that. Straightforward change. Thanks very much.
>>
>> I marked the comment to indicate that the handling for GIST and GIN
>> indexes looked dubious to me also. I had the earlier "it is safe"
>> comments but that was before we looked at the kill prior tuples issue.
> 
> ISTM I looked at this too quickly.
> 
> kill_prior_tuple is only ever set by these lines, after scan starts:
> 
>     if (!scan->xactStartedInRecovery)
>         scan->kill_prior_tuple = scan->xs_hot_dead;
> 
> which is set in indexam.c, not within any particular am. So the coding,
> as submitted, covers all index types, current and future.

That just stops more tuples from being killed in the standby. I was
thinking that we need similar conflict resolution in GiST that we do
with b-tree delete records, to stop killed tuples from being deleted
while they might still be needed in the standby.

But looking closer at GiST, it seems that GiST doesn't actually do that;
killed tuples are not removed at page splits, but only by VACUUM. So
that's not an issue after all.

--  Heikki Linnakangas EnterpriseDB   http://www.enterprisedb.com