Re: Index usage for elem-contained-by-const-range clauses

From: Pritam Baral <pritam(at)pritambaral(dot)com>
To: Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>
Cc: pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Index usage for elem-contained-by-const-range clauses
Date: 2017-03-17 21:41:28
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On Friday 10 March 2017 07:59 PM, Alexander Korotkov wrote:
> Hi, Pritam! > > I've assigned to review this patch. > > On Thu, Feb 23, 2017 at 2:17 AM, Pritam Baral <pritam(at)pritambaral(dot)com> wrote: > > The topic has been previously discussed[0] on the -performance mailing list, > about four years ago. > > In that thread, Tom suggested[0] the planner could be made to "expand > "intcol <@ > 'x,y'::int4range" into "intcol between x and y", using something similar > to the > index LIKE optimization (ie, the "special operator" stuff in indxpath.c)". > > > That's cool idea. But I would say more. Sometimes it's useful to transform "intcol between x and y" into "intcol <@ 'x,y'::int4range". btree_gin supports "intcol between x and y" as overlap of "intcol >= x" and "intcol <= y". That is very inefficient. But it this clause would be transformed into "intcol <@ 'x,y'::int4range", btree_gin could handle this very efficient. > > > > This patch tries to do exactly that. It's not tied to any specific datatype, > and has
been tested with both builtin types and custom range types. Most > of the > checking for proper datatypes, operators, and btree index happens before > this > code, so I haven't run into any issues yet in my testing. But I'm not > familiar > enough with the internals to be able to confidently say it can handle > all cases > just yet. > > > I've tried this patch. It applies cleanly, but doesn't compile. > > indxpath.c:4252:1: error: conflicting types for 'range_elem_contained_quals' > range_elem_contained_quals(Node *leftop, Datum rightop) > ^ > indxpath.c:192:14: note: previous declaration is here > static List *range_elem_contained_quals(Node *leftop, Oid expr_op, Oid opfamily, > ^ > Could you please recheck that you published right version of patch?

So sorry. I'm attaching the correct version of the original with this,
in case you want to test the limited implementation, because I still
have to go through Tom's list of suggestions.

BTW, the patch is for applying on top of REL9_6_2, and while I
suspect it may work on master too, I haven't tested it since the
original submission (Feb 23).

> Also, I noticed that patch haven't regression tests. Some mention of this optimization in docs is also nice to have. > > ------ > Alexander Korotkov > Postgres Professional: > The Russian Postgres Company

#!/usr/bin/env regards
Chhatoi Pritam Baral

Attachment Content-Type Size
use-btree-index-in-elem-contained-by-range.patch text/x-patch 6.6 KB

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