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

Gavin Wahl wrote:
> It seems trivial to accelerate a MAX or MIN query with a BRIN index. You
> just find the page range with the largest/smallest value, and then only
> scan that one. Would that be hard to implement? I'm interested in working
> on it if someone can give me some pointers.

I think this means you need to represent this operation as a specific
Path in some way.  See build_minmax_path() and its callers in planagg;
you probably need to tweak preprocess_minmax_aggregates() to consider
this.

This doesn't look like a simple project to me, mind.

> 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.

I wouldn't know where to start for this.  Maybe once Tom is done with
planner rejiggering it would make sense to consider looking at how to do
it.

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Álvaro Herrera                http://www.2ndQuadrant.com/
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