My results were exactly the same for btree and hash, even when vacumming
between each index creation. Here's my query:
SELECT * FROM prod_base WHERE mid='2';
Here's my result:
Index Scan using prod_mid_idx on prod_base (cost=2.05 rows=2 width=120)
My database is perhaps not big enough to run some relevant tests, so
please let me know if there's another way I could get a better idea of the
resources used for using each searching method.
> Run some performace tests and let us know.
>
> > I've been reading the postgresql manual and I find there is very little
> > discussion about hash compared to btree. Most of the focus seems to be on
> > using btree indices even that the default for 'create index' is btree
> > also. From the documentation, it seems the only difference between either
> > searching method is that btree can be used with multiple operators whilst
> > hash can only be used with '='. Furthermore, hash seems to be contained in
> > memory, so should be limited to small queries or, in my case, queries
> > using limit (without using sort which would need to retrieve the entire
> > data anyways).
> >
> > My conclusion is that if I can live with just using '=' and using slightly
> > more memory, I should be using hash. Unfortunately, there is very little
> > sign in the documentation that I should be using hash at all. Perhaps I
> > have missed something important.
> >
> > If someone could help me make a more rational decision on using searching
> > methods, I'd appreciate.
> >
> > Thanks in advance,
> > Marc
> >
> >
> > ************
> >
> >
>
>
> --
> Bruce Momjian | http://www.op.net/~candle
> maillist@candle.pha.pa.us | (610) 853-3000
> + If your life is a hard drive, | 830 Blythe Avenue
> + Christ can be your backup. | Drexel Hill, Pennsylvania 19026
>
