On 29/10/14 10:41, David Rowley wrote:
On Mon, Oct 13, 2014 at 11:00 AM, Tomas Vondra <t...@fuzzy.czThe last point is really just "unfinished implementation" - the syntax I propose is this: ALTER TABLE ... ADD STATISTICS (options) ON (columns) where the options influence the MCV list and histogram size, etc. The options are recognized and may give you an idea of what it might do, but it's not really used at the moment (except for storing in the pg_mv_statistic catalog). I've not really gotten around to looking at the patch yet, but I'm also wondering if it would be simple include allowing functional statistics too. The pg_mv_statistic name seems to indicate multi columns, but how about stats on date(datetime_column), or perhaps any non-volatile function. This would help to solve the problem highlighted here http://www.postgresql.org/message-id/CAApHDvp2vH=7O-gp-zAf7aWy+A-WHWVg7h3Vc6=5pf9uf34...@mail.gmail.com . Without giving it too much thought, perhaps any expression that can be indexed should be allowed to have stats? Would that be really difficult to implement in comparison to what you've already done with the patch so far?
I would not over-complicate requirements for the first version of this, I think it's already complicated enough.
Quick look at the patch suggests that it mainly needs discussion about design and particular implementation choices, there is fair amount of TODOs and FIXMEs. I'd like to look at it too but I doubt that I'll have time to do in depth review in this CF.
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