SELECT cods, elrik, ether, jaelen, sora, SUM(otter)
FROM t1
GROUP BY cods, elrik, ether, jaelen, sora
UNION ALL
SELECT 0 AS cods, 0 AS elrik, 0 AS ether, 0 AS jaelen, 0 AS sora, SUM(tib0)
FROM t2
GROUP BY cods, elrik, ether, jaelen, sora;
Actual Results:
MonetDB crashes
Expected Results:
Something..
It is interesting to note that using fewer columns doesn't trigger this bug. It's only when about 5 or more columns are used within the GROUP BY that we see this behavior.
It was rather hard to diagnostic, because we had a very large query in the first place. It tooks hours to find the very specific query that was triggering this problem.
Comment 21321
Date: 2015-10-08 15:26:51 +0200
From: Martin van Dinther <<martin.van.dinther>>
I found the issue is already reproducable (on Jul2015) with query:
SELECT 0 AS cods, 0 AS elrik, 0 AS ether, 0 AS jaelen, 0 AS sora, SUM(tib0)
FROM t2
GROUP BY cods, elrik, ether, jaelen, sora;
Also adding PLAN or EXPLAIN or TRACE in front of the query, also leads to a Segmentation fault in the mserver5.
No problem when grouping less than 5 columns as in query:
SELECT 0 AS elrik, 0 AS ether, 0 AS jaelen, 0 AS sora, SUM(tib0)
FROM t2
GROUP BY elrik, ether, jaelen, sora;
Date: 2015-10-07 18:15:09 +0200
From: Frédéric Jolliton <<frederic.jolliton+monetdb>>
To: SQL devs <>
Version: 11.17.21 (Jan2014-SP3)
CC: martin.van.dinther, @njnes
Last updated: 2015-11-03 10:18:26 +0100
Comment 21320
Date: 2015-10-07 18:15:09 +0200
From: Frédéric Jolliton <<frederic.jolliton+monetdb>>
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:41.0) Gecko/20100101 Firefox/41.0
Build Identifier:
A specific combination of UNION / GROUP BY / AGGREGATES and tables definitions causes MonetDB to crash.
The server log just tell about SIGSEGV without further details.
Reproducible: Always
Steps to Reproduce:
CREATE TABLE t1 (cods int, elrik int, ether int, jaelen int, otter int, sora int);
CREATE TABLE t2 (tib0 int);
SELECT cods, elrik, ether, jaelen, sora, SUM(otter)
FROM t1
GROUP BY cods, elrik, ether, jaelen, sora
UNION ALL
SELECT 0 AS cods, 0 AS elrik, 0 AS ether, 0 AS jaelen, 0 AS sora, SUM(tib0)
FROM t2
GROUP BY cods, elrik, ether, jaelen, sora;
Actual Results:
MonetDB crashes
Expected Results:
Something..
It is interesting to note that using fewer columns doesn't trigger this bug. It's only when about 5 or more columns are used within the GROUP BY that we see this behavior.
It was rather hard to diagnostic, because we had a very large query in the first place. It tooks hours to find the very specific query that was triggering this problem.
Comment 21321
Date: 2015-10-08 15:26:51 +0200
From: Martin van Dinther <<martin.van.dinther>>
I found the issue is already reproducable (on Jul2015) with query:
SELECT 0 AS cods, 0 AS elrik, 0 AS ether, 0 AS jaelen, 0 AS sora, SUM(tib0)
FROM t2
GROUP BY cods, elrik, ether, jaelen, sora;
Also adding PLAN or EXPLAIN or TRACE in front of the query, also leads to a Segmentation fault in the mserver5.
No problem when grouping less than 5 columns as in query:
SELECT 0 AS elrik, 0 AS ether, 0 AS jaelen, 0 AS sora, SUM(tib0)
FROM t2
GROUP BY elrik, ether, jaelen, sora;
Comment 21330
Date: 2015-10-14 11:40:36 +0200
From: MonetDB Mercurial Repository <>
Changeset d04a59d1b9a9 made by Niels Nes niels@cwi.nl in the MonetDB repo, refers to this bug.
For complete details, see http//devmonetdborg/hg/MonetDB?cmd=changeset;node=d04a59d1b9a9
Changeset description:
Comment 21331
Date: 2015-10-14 11:41:39 +0200
From: @njnes
properly handle alias expressions (and no other expressions) in the reduce group by optimizer.
Comment 21444
Date: 2015-11-03 10:18:26 +0100
From: @sjoerdmullender
Jul2015 SP1 has been released.
The text was updated successfully, but these errors were encountered: