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select * from sys.connections always returns 0 rows. Expected to see at least one row for the active connection. #3996

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


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

Date: 2016-04-28 12:34:19 +0200
From: Martin van Dinther <<martin.van.dinther>>
To: SQL devs <>
Version: 11.21.19 (Jul2015-SP4)
CC: @njnes, serinalevis9

Last updated: 2019-02-12 13:54:48 +0100

Comment 22102

Date: 2016-04-28 12:34:19 +0200
From: Martin van Dinther <<martin.van.dinther>>

User-Agent: Mozilla/5.0 (X11; Fedora; Linux x86_64; rv:45.0) Gecko/20100101 Firefox/45.0
Build Identifier:

Query: select * from sys.connections;
should list the connections conencted on the MonetDB server.
However it always returns no rows, no matter how many clients (mclient or JdbcClient or other connections) are connected to the MonetDB server.

This makes it impossible to find out who's or which clients are connected to the server.

Reproducible: Always

Steps to Reproduce:

  1. start mserver5 process (Jul2105)
  2. start mclient
  3. execute SQL query: select * from sys.connections;
  4. start a second mclient with the same credentials
  5. execute SQL query: select * from sys.connections;

Actual Results:

bash-4.3$ ./
builtin opt gdk_dbpath = /export/scratch2/dinther/INSTALL/var/monetdb5/dbfarm/demo
builtin opt gdk_debug = 0
builtin opt gdk_vmtrim = no
builtin opt monet_prompt = >
builtin opt monet_daemon = no
builtin opt mapi_port = 50000
builtin opt mapi_open = false
builtin opt mapi_autosense = false
builtin opt sql_optimizer = default_pipe
builtin opt sql_debug = 0
cmdline opt embedded_r = true
cmdline opt mapi_port = 41000
cmdline opt gdk_debug = 10
MonetDB 5 server v11.21.20
This is an unreleased version
Serving database 'demo', using 8 threads
Compiled for x86_64-unknown-linux-gnu/64bit with 64bit OIDs and 128bit integers dynamically linked
Found 15.589 GiB available main-memory.
Copyright (c) 1993-July 2008 CWI.
Copyright (c) August 2008-2015 MonetDB B.V., all rights reserved
Visit for further information
Listening for connection requests on mapi:monetdb://
MonetDB/GIS module loaded
Start processing logs sql/sql_logs version 52200
Finished processing logs sql/sql_logs
MonetDB/SQL module loaded
MonetDB/R module loaded

SQL catalog created, loading sql scripts once
loading sql script: 09_like.sql
loading sql script: 10_math.sql
loading sql script: 11_times.sql
loading sql script: 12_url.sql
loading sql script: 13_date.sql
loading sql script: 14_inet.sql
loading sql script: 15_querylog.sql
loading sql script: 16_tracelog.sql
loading sql script: 17_temporal.sql
loading sql script: 20_vacuum.sql
loading sql script: 21_dependency_functions.sql
loading sql script: 22_clients.sql
loading sql script: 23_skyserver.sql
loading sql script: 24_zorder.sql
loading sql script: 25_debug.sql
loading sql script: 26_sysmon.sql
loading sql script: 27_rejects.sql
loading sql script: 39_analytics.sql
loading sql script: 39_analytics_hge.sql
loading sql script: 40_geom.sql
loading sql script: 40_json.sql
loading sql script: 40_json_hge.sql
loading sql script: 41_md5sum.sql
loading sql script: 45_uuid.sql
loading sql script: 46_gsl.sql
loading sql script: 51_sys_schema_extension.sql
loading sql script: 72_fits.sql
loading sql script: 74_netcdf.sql
loading sql script: 75_storagemodel.sql
loading sql script: 80_statistics.sql
loading sql script: 80_udf.sql
loading sql script: 80_udf_hge.sql
loading sql script: 85_bam.sql
loading sql script: 90_generator.sql
loading sql script: 90_generator_hge.sql
loading sql script: 99_system.sql

bash-4.3$ mclient
Welcome to mclient, the MonetDB/SQL interactive terminal (unreleased)
Database: MonetDB v11.21.20 (unreleased), 'demo'
Type \q to quit, ? for a list of available commands
auto commit mode: on
sql>select * from sys.connections;
| id | server | port | db | db_alias | user | password | language |
0 tuples (2.079ms)

Expected Results:

For each connected client program or connection, a row listing the connection information.
When using mclient it should list at least one row; the connection made by mclient.

Comment 22189

Date: 2016-05-30 17:11:06 +0200
From: @sjoerdmullender

The table sys.connections has nothing to do with MAPI connections. It is a remnant from experimental code which was removed in February 2012 (changeset 8ee024048e42).

The bug is rather that the table still exists.

Comment 22307

Date: 2016-08-19 16:00:37 +0200
From: @njnes

should we cleanup the mvc_connect_catalog code (including this table)?

Comment 22327

Date: 2016-08-29 11:41:11 +0200
From: @sjoerdmullender

(In reply to Niels Nes from comment 2)

should we cleanup the mvc_connect_catalog code (including this table)?


Comment 24980

Date: 2017-02-06 22:20:16 +0100
From: MonetDB Mercurial Repository <>

Changeset 873075e01254 made by Sjoerd Mullender in the MonetDB repo, refers to this bug.

For complete details, see http//devmonetdborg/hg/MonetDB?cmd=changeset;node=873075e01254

Changeset description:

Removed table sys.connections.
This "fixes" bug #3996.

Comment 24981

Date: 2017-02-06 22:24:53 +0100
From: @sjoerdmullender

The sys.connections table will be removed in the next feature release. This should end the confusion.

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