Re: Full text search with ORDER BY performance issue

On Tue, 21 Jul 2009, valgog wrote:
> There is a problem with GIN and GIST indexes, that they cannot be used
> by the ORDER BY. Maybe it will be a nice idea to ask Oleg to make it
> possible to use the b-tree columns in GIST or GIN to make the sort
> easier, but I have no idea how difficult it will be to implement it in
> current GIN or GIST structures. I think Oleg or even Tom will be the
> right people to ask it :)

I can answer that one for GiST, having had a good look at GiST recently.
There is simply no useful information about order in a GiST index for it
to be used by an ORDER BY. The index structure is just too general,
because it needs to cope with the situation where a particular object type
does not have a well defined order, or where the "order" is unuseful for
indexing.

Matthew

--
 A good programmer is one who looks both ways before crossing a one-way street.
 Considering the quality and quantity of one-way streets in Cambridge, it
 should be no surprise that there are so many good programmers there.