From: Tom Lane <tgl@sss.pgh.pa.us>
To: Ashutosh Bapat <ashutosh.bapat@enterprisedb.com>
Cc: pgsql-hackers <pgsql-hackers@postgresql.org>
Subject: Re: WIP patch: distinguish selectivity of < from <= and > from >=
Date: Tue, 04 Jul 2017 10:59:10 -0400
Message-ID: <2277.1499180350@sss.pgh.pa.us> (raw)
In-Reply-To: <CAFjFpReiJNoOqOLksX3CQkeig8RVU+O7mz9OgPuuoCQLCAqTKw@mail.gmail.com>
References: <12232.1499140410@sss.pgh.pa.us>
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Ashutosh Bapat <ashutosh.bapat@enterprisedb.com> writes:
> On Tue, Jul 4, 2017 at 9:23 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> regression=# explain analyze select * from tenk1 where thousand < 10;
>> before:
>> Bitmap Heap Scan on tenk1 (cost=5.14..241.38 rows=110 width=244) (actual time=0.121..0.623 rows=100 loops=1)
>> with patch:
>> Bitmap Heap Scan on tenk1 (cost=5.06..227.42 rows=100 width=244) (actual time=0.054..0.300 rows=100 loops=1)
> It's expected that the estimates will change with this patch. But I am
> wondering why should actual times vary so much. May be that's just
> accidental. Butthe actual timings are consistently lower with the
> patch except the last one
I didn't intend those examples to illustrate anything except row counts,
so I didn't worry about making the timings comparable. Some of the
examples were probably the first query in a session and so would've faced
cache-populating costs the others didn't. Also, the "before" examples
were all done on 9.6 not HEAD.
regards, tom lane
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To: pgsql-hackers@postgresql.org
Cc: tgl@sss.pgh.pa.us, ashutosh.bapat@enterprisedb.com
Subject: Re: WIP patch: distinguish selectivity of < from <= and > from >=
In-Reply-To: <2277.1499180350@sss.pgh.pa.us>
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