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Select from remote table leaves session open #6548

monetdb-team opened this issue Nov 30, 2020 · 0 comments

Select from remote table leaves session open #6548

monetdb-team opened this issue Nov 30, 2020 · 0 comments


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@monetdb-team monetdb-team commented Nov 30, 2020

Date: 2018-02-27 11:50:10 +0100
From: Nick <>
To: SQL devs <>
Version: 11.27.13 (Jul2017-SP4)
CC: @njnes

Last updated: 2018-03-29 15:39:16 +0200

Comment 26231

Date: 2018-02-27 11:50:10 +0100
From: Nick <>

User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:58.0) Gecko/20100101 Firefox/58.0
Build Identifier:

I have two databases (v11.27.13 both) on two Debian8 machines. One with
corrupted table (in my case it got corrupted due to bug in Jul2017-SP1) and
another with remote table to the corrupted table. When I run the SELECT
query on the remote table I get an error. And the session opened by this
query to the first DB did not close. I see it by querying 'sys.sessions'
table. And every time I run this SELECT I get additional record in
'sys.sessions'. This happens only if en error occurs, on successful SELECT
the session immediately disappears. How can I force this sessions to close
or is it a bug?

Reproducible: Always

Steps to Reproduce:

  1. Have two instances on MonetDB with 'storage' databases in each.
  2. In the first instance create regular table like this:
    create table storage.ttt(col1 varchar(10));
  3. Fill it with some data.
  4. Corrupt this table somehow (Don't know how to reproduce this step. I got it corrupted accidentally due to bug in Jul2017-SP1)
  5. In the second instance create remote table to the table created in step 2:
    create remote table storage.ttt(col1 varchar(10))ON 'mapi:monetdb://:50000/storage';
  6. Check opened sessions on the first instance by running the query under 'monetdb' user:
    select * from sys.sessions;
    1 tuple (3.907ms)
  7. Run query on remote table:
    select * from storage.ttt;
    and get an error about corrupted BAT or something.
  8. Check opened sessions again and the additional inactive session will be listed which will never close.

Actual Results:

Increasing number of inactive sessions from the second instance.

Expected Results:

Close each session after query on the remote table has failed.

mserver5 --version
MonetDB 5 server v11.27.13 "Jul2017-SP4" (64-bit, 128-bit integers)
Copyright (c) 1993 - July 2008 CWI
Copyright (c) August 2008 - 2018 MonetDB B.V., all rights reserved
Visit for further information
Found 11.8GiB available memory, 4 available cpu cores
libpcre: 8.35 2014-04-04 (compiled with 8.35)
openssl: OpenSSL 1.0.1t 3 May 2016 (compiled with )
libxml2: 2.9.1 (compiled with 2.9.1)
Compiled by: (x86_64-pc-linux-gnu)
Compilation: gcc -O3 -fomit-frame-pointer -pipe -g -D_FORTIFY_SOURCE=2
Linking : /usr/bin/ld -m elf_x86_64

Comment 26232

Date: 2018-02-27 14:26:05 +0100
From: Nick <>

In my case the error I got on step 8 is:
Cannot subtract delete column
BATdiff: inputs not compatible.

Comment 26260

Date: 2018-03-14 11:46:27 +0100
From: MonetDB Mercurial Repository <>

Changeset a20ec2286704 made by Niels Nes in the MonetDB repo, refers to this bug.

For complete details, see https//devmonetdborg/hg/MonetDB?cmd=changeset;node=a20ec2286704

Changeset description:

fixes for bug #6548 (ie add exception block to catch exceptions and disconnect from the
remote mserver)

also fixed problem in newExitStmt, don't push a newAssignment statement
as that is allready pushed.

Comment 26261

Date: 2018-03-14 11:47:50 +0100
From: @njnes

solved by an exception block

Comment 26315

Date: 2018-03-29 15:39:16 +0200
From: @sjoerdmullender

The Mar2018 version has been released.

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