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From:Rob Steele Date:January 28 2003 9:20pm
Subject:Server crash selecting from merge table
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>Description:

Certain queries on merge tables reliably fail or crash the server as the script below
demonstrates.

	
>How-To-Repeat:

Run this script:

#! /bin/bash

# This script demonstrates a bug in the way MySQL handles merge tables.  The bug depends
on
# the index; it doesn't manifest if there is no index or if the fields are indexed
separately.

mysql -vv << EOF

USE test;

DROP TABLE IF EXISTS a;
DROP TABLE IF EXISTS b;
DROP TABLE IF EXISTS c;


# Create two tables with the same definition.

CREATE TABLE a (
  ID      INT NOT NULL,
  Date    DATE NOT NULL,
  KEY     (ID, Date)
);

CREATE TABLE b (
  ID      INT NOT NULL,
  Date    DATE NOT NULL,
  KEY     (ID, Date)
);


# Populate the tables.

INSERT INTO a (ID, Date) VALUES (1, '2002-01-01'), (1, '2002-01-02'), (1, '2002-01-03');

INSERT INTO b (ID, Date) VALUES (1, '2002-02-01'), (1, '2002-02-02'), (1, '2002-02-03');


# Create a merge table combining the previous two.

CREATE TABLE c (
  ID      INT NOT NULL,
  Date    DATE NOT NULL,
  KEY     (ID, Date)
) TYPE=MERGE UNION=(a, b);



# This works.
SELECT MIN(Date) FROM c WHERE ID = 1;

# This fails by returning NULL.
SELECT MAX(Date) FROM c WHERE ID = 1;

# Going straight to the component tables works though.
SELECT MAX(Date) FROM a WHERE ID = 1;
SELECT MAX(Date) FROM b WHERE ID = 1;

# The different results from these might be a clue.
EXPLAIN SELECT MIN(Date) FROM c WHERE ID = 1;
EXPLAIN SELECT MAX(Date) FROM c WHERE ID = 1;

# This crashes the server.
SELECT MIN(Date), MAX(Date) FROM c WHERE ID = 1;

EOF


>Fix:
>Submitter-Id:	<submitter ID>
>Originator:	Rob Steele
>Organization:  FatKat, Inc.
>MySQL support: none
>Synopsis:	Selecting from merge table crashes server
>Severity:	serious
>Priority:	high
>Category:	mysql
>Class:		sw-bug
>Release:	mysql-3.23.54 (Official MySQL RPM)
>Server: /usr/bin/mysqladmin  Ver 8.23 Distrib 3.23.54, for pc-linux on i686
Copyright (C) 2000 MySQL AB & MySQL Finland AB & TCX DataKonsult AB
This software comes with ABSOLUTELY NO WARRANTY. This is free software,
and you are welcome to modify and redistribute it under the GPL license

Server version		3.23.54-Max
Protocol version	10
Connection		Localhost via UNIX socket
UNIX socket		/tmp/mysql.sock
Uptime:			7 min 44 sec

Threads: 1  Questions: 1  Slow queries: 0  Opens: 6  Flush tables: 1  Open tables: 0
Queries per second avg: 0.002
>Environment:
	
System: Linux warren.fatkat.com 2.4.18-19.8.0 #1 Thu Dec 12 05:39:29 EST 2002 i686 i686
i386 GNU/Linux
Architecture: i686

Some paths:  /usr/bin/perl /usr/bin/make /usr/bin/gmake /usr/bin/gcc /usr/bin/cc
GCC: Reading specs from /usr/lib/gcc-lib/i386-redhat-linux/3.2/specs
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man
--infodir=/usr/share/info --enable-shared --enable-threads=posix --disable-checking
--host=i386-redhat-linux --with-system-zlib --enable-__cxa_atexit
Thread model: posix
gcc version 3.2 20020903 (Red Hat Linux 8.0 3.2-7)
Compilation info: CC='gcc'  CFLAGS='-O6 -fno-omit-frame-pointer -mpentium'  CXX='gcc' 
CXXFLAGS='-O6 -fno-omit-frame-pointer 	          -felide-constructors -fno-exceptions
-fno-rtti -mpentium'  LDFLAGS=''
LIBC: 
lrwxrwxrwx    1 root     root           14 Oct  2 19:15 /lib/libc.so.6 ->
libc-2.2.93.so
-rwxr-xr-x    1 root     root      1235468 Sep  5 19:12 /lib/libc-2.2.93.so
-rw-r--r--    1 root     root      2233342 Sep  5 18:59 /usr/lib/libc.a
-rw-r--r--    1 root     root          178 Sep  5 18:50 /usr/lib/libc.so
lrwxrwxrwx    1 root     root           10 Oct  2 19:53 /usr/lib/libc-client.a ->
c-client.a
Configure command: ./configure '--disable-shared' '--with-mysqld-ldflags=-all-static'
'--with-client-ldflags=-all-static' '--without-berkeley-db' '--without-innodb'
'--enable-assembler' '--enable-local-infile' '--with-mysqld-user=mysql'
'--with-unix-socket-path=/var/lib/mysql/mysql.sock' '--prefix=/'
'--with-extra-charsets=complex' '--exec-prefix=/usr' '--libexecdir=/usr/sbin'
'--sysconfdir=/etc' '--datadir=/usr/share' '--localstatedir=/var/lib/mysql'
'--infodir=/usr/share/info' '--includedir=/usr/include' '--mandir=/usr/share/man'
'--with-comment=Official MySQL RPM' 'CC=gcc' 'CFLAGS=-O6 -fno-omit-frame-pointer
-mpentium' 'CXXFLAGS=-O6 -fno-omit-frame-pointer 	          -felide-constructors
-fno-exceptions -fno-rtti -mpentium' 'CXX=gcc'

Thread
Server crash selecting from merge tableRob Steele28 Jan