Re: BRIN indexes for MAX, MIN, ORDER BY?

On 29 September 2015 at 13:20, Jeremy Harris <jgh(at)wizmail(dot)org> wrote:

> On 27/09/15 21:58, Gavin Wahl wrote:
> > Somewhat harder but still possible would be using BRIN indexes to
> > accelerate ORDER BY. This would require a sorting algorithm that can take
> > advantage of mostly-sorted inputs. You would sort the page ranges by
> their
> > minimum or maximum value, then feed the sorting algorithm in that order.
>
> An internal merge sort does well with partially-sorted input.
>

Yes, the $SUBJECT would be a valid use for BRIN.

And also in general for sorts, leading to an optimization of merge joins
using BRIN indexes.

All this was foreseen in the original design; if it really was trivial it
would be in 9.5 already...

--
Simon Riggs http://www.2ndQuadrant.com/
<http://www.2ndquadrant.com/>
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services