Re: [PATCH]-hash index improving

On Thu, 2008-07-17 at 16:37 -0700, Dann Corbit wrote:

> Large table unique index equality search should be very fast with hashed
> index (and the only place where any advantage will be seen).  Hashed
> indexes are useless for any search besides equality and gain more and
> more when the levels of the b-tree index increase.

I think a comparison with a btree using a functional index should be
shown.

> The only way to get better performance from hash based indexes is to
> read fewer index pages than if a tree-based index were used.  So I think
> that the scheme used to create the index pages is the focus to make them
> worthwhile.

Agreed. Some math on that, plus a clear focus on making this faster than
a btree is critical to this project.

-- Simon Riggs           www.2ndQuadrant.comPostgreSQL Training, Services and Support