>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'
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