Date: Sun, 12 Jul 2020 19:58:54 -0400
From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Cc: Masahiko Sawada <masahiko.sawada@2ndquadrant.com>,
	Alexander Korotkov <a.korotkov@postgrespro.ru>,
	Michael Paquier <michael@paquier.xyz>, Tom Lane <tgl@sss.pgh.pa.us>,
	Andres Freund <andres@anarazel.de>,
	Mark Dilger <hornschnorter@gmail.com>,
	pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: WIP: BRIN multi-range indexes
Message-ID: <20200712235854.GA21540@alvherre.pgsql>
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On 2020-Jul-10, Tomas Vondra wrote:

> > postgres(1:12801)=# select * from brin_page_items(get_raw_page('mul',
> > 2), 'mul');
> > -[ RECORD 1 ]----------------------------------------------------------------------------------------------------------------------
> > -----------------------------------------------------------------------------------------------------------------------------------
> > ----------------------------
> > itemoffset  | 1
> > blknum      | 0
> > attnum      | 1
> > allnulls    | f
> > hasnulls    | f
> > placeholder | f
> > value       | {\x010000001b0000002000000001000000e5700000e6700000e7700000e8700000e9700000ea700000eb700000ec700000ed700000ee700000ef
> > 700000f0700000f1700000f2700000f3700000f4700000f5700000f6700000f7700000f8700000f9700000fa700000fb700000fc700000fd700000fe700000ff700
> > 00000710000}
> 
> Hmm. I'm not sure we can do much better, without making the function
> much more complicated. I mean, even with regular BRIN indexes we don't
> really know if the value is plain min/max, right?

Maybe we can try to handle this with some other function that interprets
the bytea in 'value' and returns a user-readable text.  I think it'd
have to be a superuser-only function, because otherwise you could easily
cause a crash by passing a value of a different opclass.  But since this
seems a developer-only thing, that restriction seems fine to me.

(I don't know what's a good way to represent a bloom filter, mind.)

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services