Bugs item #1796269, was opened at 2007-09-17 14:53
Message generated for change (Comment added) made by nielsnes
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Category: SQL/Core
Group: (zombie: MonetDB5 5.0)
>Status: Closed
>Resolution: Fixed
Priority: 5
Private: No
Submitted By: Sandor Heman (saanti)
Assigned to: Niels Nes (nielsnes)
Summary: SQL: hangs/crashes on 'exists' subqueries after a join
Initial Comment:
This query came up during ADT labwork session 1.
We use the VOC dataset, 32-bit/32-bit-oid mserver 5, Mars SR2, on UvA linux
machines:
uname -a
Linux ow126 2.6.12-1.1381_FC3smp #1 SMP Fri Oct 21 04:03:26 EDT 2005 i686 i686
i386 GNU/Linux
The original query hangs mserver without any resource consumption:
select count(*) from
craftsmen c,
passengers p
where c.trip = p.trip and exists
(select 1 from voyages v
where c.trip = v.trip and v.boatname = 'AMSTERDAM'
and v.departure_harbour ='Texel');
When reducing it to the below query, the server segfaults:
select count(*)
from craftsmen c,
passengers p
where c.trip = p.trip and exists (select 1) ;
without a join we get for both:
select count(*) from craftsmen c ;
select count(*) from craftsmen c where exists (select 1) ;
BOTH GIVE:
+--------+
| count_ |
+========+
| 2349 |
+--------+
1 row
----------------------------------------------------------------------
>Comment By: Niels Nes (nielsnes)
Date: 2007-11-19 18:12
Message:
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added these queries to the VOC test in src/test/VOC.
Fixed in 2 parts. 1) use dynamic hash sizes for the exist part of the
first query. 2) exists(select 1)
is now handled properly (old incorrect code did one join to much leading
to large results)
----------------------------------------------------------------------
Comment By: Martin Kersten (mlkersten)
Date: 2007-11-16 12:15
Message:
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Niels, can it be closed?
----------------------------------------------------------------------
Comment By: Martin Kersten (mlkersten)
Date: 2007-09-18 21:39
Message:
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This bug is not confirmed on the head MonetDB/SQL
There is no segfault
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