Re: CREATE INDEX and HOT (was Question: pg_classattributes and race conditions ?)

On Mon, 2007-03-19 at 10:51 +0000, Heikki Linnakangas wrote:
> Pavan Deolasee wrote:
> > Heikki Linnakangas wrote:
> > > Pavan Deolasee wrote:
> > > We would only need the extra byte in HOT-updated tuples.
> > Alternatively, we could use the bits we have free in infomask2. There's
> > currently 5 bits free, using just 2 or 3 of those would get us quite
> > far. Or just one, which would be the Tom's suggestion of only using HOT
> > for tables with a single index.
> > >
> >
> > We've already used three of those, two for tracking HEAP_ONLY
> > and HOT_UPDATED tuples and one for tracking fragmented tuple.
>
> HEAP_ONLY_TUPLE would go away in favor of the per-index bits. So we have
> bits available for three indexes.

ISTM that we are getting very close to a great idea here.

I was unwilling to compromise to have HOT if only one index existed, but
IMHO allowing HOT with <= 3 indexes is an acceptable compromise for this
release. (We can always use vertical partitioning techniques to allow
additional access paths to be added to the same table - I'd be very
happy to document that with worked examples, if requried).

I trust that we will think of ways of extending that limit in later
releases.

--
Simon Riggs
EnterpriseDB http://www.enterprisedb.com