Re: SSI patch version 14

On Mon, 2011-01-31 at 14:38 -0600, Kevin Grittner wrote:
> It is at least as likely that I'm missing something. If I'm
> following you, we're talking about these 24 lines of code, where
> "valid" is the what was just returned from
> HeapTupleSatisfiesVisibility:

Yes.

> (1) Do you see a case where this would do the wrong thing? Can you
> describe that or (even better) provide a test case to demonstrate
> it?

No, I don't see any incorrect results.

> (2) I haven't gotten my head around how HTSV helps or is even the
> right thing.

It primarily just encapsulates the access to the tuple header fields. I
think that avoiding the messy logic of hint bits, tuple locks, etc., is
a significant win for readability and maintainability.

> If I want to try the switch statement from your recent
> post, what should I use as the OldestXmin value on the call to HTSV?

I believe RecentGlobalXmin should work.

And I don't think the original switch statement I posted did the right
thing for HEAPTUPLE_LIVE. I think that case needs to account for the
visible flag (if it's live but not visible, that's the same as
insert-in-progress for your purposes).

Regards,
Jeff Davis