Re: CLUSTER and indisclustered

On Sat, 3 Aug 2002, Tom Lane wrote:

> Gavin Sherry <swm@linuxworld.com.au> writes:
> > It occured to me on the plane home that now that CLUSTER is fixed we may
> > be able to put pg_index.indisclustered to use. If CLUSTER was to set
> > indisclustered to true when it clusters a heap according to the given
> > index, we could speed up sequantial scans.
> 
> AFAICT you're assuming that the table is *exactly* ordered by the
> clustered attribute.  While this is true at the instant CLUSTER
> completes, the exact ordering will be destroyed by the first insert or
> update :-(.  I can't see much value in creating a whole new scan type

Sorry, I meant to say that heap_insert() etc would need to set
indisclustered to false.

I do see some worth in this however. Naturally, in a situation where a
database is being modified very often this is of little value. However,
for applications focussed on analysing large amounts of static data this
could increase performance significantly. Once I get some time I will
attempt to explore this further in `diff -c` format :-).

Gavin