Re: B-tree performance improvements in 8.x

jao@geophile.com writes:
> Quoting Tom Lane <tgl@sss.pgh.pa.us>:
>> In 8.0, the descent code can do
>> either "first entry >= X" or "first entry > X", and the positioning
>> rules never need to step more than one entry to locate the desired
>> starting position (details left as exercise for the reader).

> What about a compound index (x, y), in which there are many y values
> for a given x? My query is "... WHERE x = ? and y = ?".

Doesn't really matter whether the key is simple or compound --- all
that matters is whether you have multiple entries that are "equal" to
the boundary value.

            regards, tom lane