>Description:
There is an apparent bug in the optimiser which causes it
to go into an infinite loop when presented with complex queries.
I know the problem is in the optimiser becaues the query in question
still hangs the thread (and effectively the server) in a cpu-intensive
loop with just an "explain ..." I can demonstrate the bug on:
FreeBSD 2.2.7 x86 MySQL-3.21.33b MIT-pthreads
FreeBSD 3.0.0 x86 MySQL-3.21.33b MIT-pthreads
FreeBSD 3.0.0 x86 3.22.14b-gamma MIT-pthreads
FreeBSD 3.0.0 x86 3.22.14b-gamma native pthreads
I have not tried other combinations.
The query which provokes this is addmittedly very complex, but is
automatically generated and so difficult to alter. My intention
with such a query would be to calculate the cost of the query by
multiplying up the "rows" field returned by the "explain", then reject
the query if too expensive.
>How-To-Repeat:
sql script recreating the problem ftp'd to
ftp://www.mysql.com/pub/mysql/secret/billh.sql
>Fix:
>Submitter-Id: [EMAIL PROTECTED]
>Originator: Bill Hails
>Organization:
Yahoo! Europe
>MySQL support: none
>Synopsis: explain hangs, multiple versions/platforms
>Severity: serious
>Priority: high
>Category: mysql
>Class: sw-bug
>Release: mysql-3.22.14b-gamma (Source distribution)
>Server: /usr/local/bin/mysqladmin Ver 7.8 Distrib 3.22.14b-gamma, for
>unknown-freebsd3.0.0 on i386
TCX Datakonsult AB, by Monty
Server version 3.22.14b-gamma-log
Protocol version 10
Connection localhost via TCP/IP
TCP port 3306
Uptime: 18 sec
Threads: 1 Questions: 1 Slow queries: 0 Opens: 6 Flush tables: 1 Open tables: 2
>Environment:
System: FreeBSD db1.europe.yahoo.com 3.0.0-19990112-SNAP FreeBSD 3.0.0-19990112-SNAP
#0: Sat Jan 16 04:39:51 GMT 1999
[EMAIL PROTECTED]:/usr/src/sys/compile/DB1 i386
Some paths: /usr/bin/perl /usr/bin/make /usr/bin/gcc /usr/bin/cc
GCC: gcc version 2.7.2.1
Compilation info: CC='gcc' CFLAGS='' CXX='gcc' CXXFLAGS='' LDFLAGS=''
Configure command: ./configure --with-unix-socket-path=/var/tmp/mysql.sock
--with-low-memory --with-mit-threads=yes
Perl: This is perl, version 5.005_02 built for i386-freebsd
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