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Date: Mon, 18 Mar 2019 19:26:40 +0100
From: Matthias Otterbach <mo@otterbach.eu>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #15700: PG 10 vs. 11: Large increase in memory usage when
 selecting BYTEA data (maybe memory leak)
In-Reply-To: <16717.1552926811@sss.pgh.pa.us>
References: <15700-8c408321a87d56bb@postgresql.org>
 <16717.1552926811@sss.pgh.pa.us>
Message-ID: <4ef5f38d5710c4d5c289537c588c7335@otterbach.eu>
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Dear Tom Lane, dear pgsql-bugs list,

thanks for your reply and attempt to reproduce my memory issue.

Am 2019-03-18 17:33, schrieb Tom Lane:
> PG Bug reporting form <noreply@postgresql.org> writes:
> 
>> I know that I'm also using the JDBC driver here which of course could 
>> also
>> cause the bug, it might be a JDBC driver bug for which I should report 
>> a bug
>> elsewhere.
> 
> I confess that I'm not actually trying this with JDBC, but with
> libpq (via psql and pgbench).  One could imagine that JDBC is
> presenting the query sufficiently differently to cause different
> backend behavior, say by asking for binary not text output ---
> but I tried that, no change.

Can I do anything to figure out how the JDBC driver presents the query? 
Is there any information available if I increase a log level or enable 
any debugging output in the PostgreSQL server?

I tried increasing log levels a little bit, but actually I do not know 
if it gives any more information:

log_min_messages = debug5
log_min_error_statement = debug5

debug_print_parse = on
debug_print_rewritten = on
debug_print_plan = on
debug_pretty_print = on
log_connections = on
log_disconnections = on
log_duration = on
log_error_verbosity = verbose

You can find an extract from the logfile at 
https://pastebin.com/5eB0t0uS (filtered for my process id which caused 
the crash even though there were not many other processes as I use this 
virtual machine solely for this test query).

> I think there must be some other moving parts you haven't mentioned.
> Maybe you have some PG extension(s) installed?

Actually I hope not, that is why I tried to reproduce the problem with a 
vanilla Ubuntu and PostgreSQL installation in a virtual machine - to 
make sure that there are no other extensions or anything influence my 
issue. Actually "postgres=# select * from pg_extension;" returns:

  extname | extowner | extnamespace | extrelocatable | extversion | 
extconfig | extcondition
---------+----------+--------------+----------------+------------+-----------+--------------
  plpgsql |       10 |           11 | f              | 1.0        |       
     |
(1 row)

Best regards, Matthias Otterbach