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 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

Álvaro Herrera      
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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