Re: Multicolumn hash indexes

Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> Maybe you're worrying about something like a billion-row table where
> there are 3 columns that form a composite key: (1,1,1), (1,1,2), ...,
> (1,1000),(1,2,1),...,(1,1000,1000),(2,1,1),...,(1000,1000,1000). In
> that case, treating the leading column as most important will indeed
> be terrible, since we'll put all billion rows into 1000 buckets no
> matter how many bucket splits we do.

> That seems a little unusual, though.

There are few if any indexing techniques where the first column isn't
significantly more important than the rest --- certainly that's true
for btree, for example. I do not think it's a showstopper if that's
true for hash as well.

regards, tom lane