	>> > Would a rule be that
	>> > if the first attribute of an index is unique, then additional
	>> > attributes are basically useless?
	>>  
<< cut some of my nonsense here >> 

	David Gould writes:
	>The rule 'if the first attribute of an index is unique, then
additional
	>attributes are basically useless' is exactly correct for all
systems, not
	>just PostgreSQL. It has nothing to do with whether indexes are used
for
	>'orderby'.

The second Ooops in one day, I guess I have to relearn the meaning of
"First think then talk.", Sorry.  (what a day, well at least the sun is
shining here :-) 
But to speak in self defense there is still one case where the trailing 
columns in this index would help. If only index columns are selected,
the engine could do an index only scan (not in postgresql yet).

Andreas



Tue, 31 Mar 1998 09:48:39 +0200
Zeugswetter Andreas SARZ <Andreas.Zeugswetter@telecom.at>
Re: [HACKERS] Re: Let's talk up 6.3