From: Tomas Vondra <tomas.vondra@2ndquadrant.com>
To: Andres Freund <andres@anarazel.de>
Cc: Justin Pryzby <pryzby@telsasoft.com>
Cc: pgsql-hackers@lists.postgresql.org, Jeff Janes <jeff.janes@gmail.com>
Subject: Re: explain HashAggregate to report bucket and memory stats
Date: Fri, 6 Mar 2020 20:43:07 +0100
Message-ID: <20200306194307.qeobgf3bklqodecv@development> (raw)
In-Reply-To: <20200306175859.d56ohskarwldyrrw@alap3.anarazel.de>
References: <20200103161925.GM12066@telsasoft.com>
<20200203145301.53mozz7gcdaklnjc@alap3.anarazel.de>
<20200216000220.GF31889@telsasoft.com>
<20200216175307.GJ31889@telsasoft.com>
<20200219201037.GA21433@telsasoft.com>
<20200222215335.bu4kky7el4nccls5@development>
<20200225033532.GX31889@telsasoft.com>
<20200301154540.GL29456@telsasoft.com>
<20200306175859.d56ohskarwldyrrw@alap3.anarazel.de>
On Fri, Mar 06, 2020 at 09:58:59AM -0800, Andres Freund wrote:
> ...
>
>> + }
>> + else if (!inst->nbuckets)
>> + ; /* Do nothing */
>> + else
>> + {
>> + if (inst->nbuckets_original != inst->nbuckets)
>> + {
>> + ExplainIndentText(es);
>> + appendStringInfo(es->str,
>> + "Buckets: %ld (originally %ld)",
>> + inst->nbuckets,
>> + inst->nbuckets_original);
>> + }
>> + else
>> + {
>> + ExplainIndentText(es);
>> + appendStringInfo(es->str,
>> + "Buckets: %ld",
>> + inst->nbuckets);
>> + }
>> +
>> + if (es->analyze)
>> + appendStringInfo(es->str,
>> + " Memory Usage: hashtable: %ldkB, tuples: %ldkB",
>> + spacePeakKb_hash, spacePeakKb_tuples);
>> + appendStringInfoChar(es->str, '\n');
>
>I'm not sure I like the alternative output formats here. All the other
>fields are separated with a comma, but the original size is in
>parens. I'd probably just format it as "Buckets: %lld " and then add
>", Original Buckets: %lld" when differing.
>
FWIW this copies hashjoin precedent, which does this:
appendStringInfo(es->str,
"Buckets: %d (originally %d) Batches: %d (originally %d) Memory Usage: %ldkB\n",
hinstrument.nbuckets,
...
I agree it's not ideal, but maybe let's not invent new ways to format
the same type of info.
regards
--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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To: pgsql-hackers@postgresql.org
Cc: tomas.vondra@2ndquadrant.com, andres@anarazel.de, pryzby@telsasoft.com, jeff.janes@gmail.com
Subject: Re: explain HashAggregate to report bucket and memory stats
In-Reply-To: <20200306194307.qeobgf3bklqodecv@development>
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