manual.texi:

SELECT * FROM tbl_name WHERE auto_col IS NULL

@end example

@item

@code{CREATE TABLE} automatically commits the current InnoDB

transaction if the MySQL binlogging is used.

@item

@code{NULL} values are handled differently for @code{TIMESTAMP} columns than

for other column types.  You cannot store a literal @code{NULL} in a

@item

In MySQL Version 3.23.44 or later, @code{InnoDB} tables support checking of

foreign key constraints. @xref{InnoDB}.

foreign key constraints. @xref{InnoDB}. Note that the

@code{FOREIGN KEY} syntax in InnoDB is more restricted than

the syntax presented above. InnoDB does not allow

@code{index_name} to be specified, and the columns of the referenced

table always have to be explicitly named. Of actions, InnoDB supports

only @code{ON DELETE CASCADE} and @code{ON DELETE SET NULL}.

See the InnoDB manual section for the precise syntax.

For other table types, MySQL Server does parse the @code{FOREIGN KEY},

@code{CHECK}, and @code{REFERENCES} syntax in @code{CREATE TABLE} commands,

but without further action being taken. @xref{ANSI diff Foreign Keys}.

  or    ADD PRIMARY KEY (index_col_name,...)

  or    ADD UNIQUE [index_name] (index_col_name,...)

  or    ADD FULLTEXT [index_name] (index_col_name,...)

  or	ADD [CONSTRAINT symbol] FOREIGN KEY index_name (index_col_name,...)

  or	ADD [CONSTRAINT symbol] FOREIGN KEY [index_name] (index_col_name,...)

            [reference_definition]

  or    ALTER [COLUMN] col_name @{SET DEFAULT literal | DROP DEFAULT@}

  or    CHANGE [COLUMN] old_col_name create_definition

@cindex foreign keys

@cindex references

The @code{FOREIGN KEY}, @code{CHECK}, and @code{REFERENCES} clauses don't

actually do anything.  The syntax for them is provided only for compatibility,

actually do anything, except for InnoDB type tables which support

@code{ADD CONSTRAINT FOREIGN KEY (...) REFERENCES ... (...)}.

Note that InnoDB does not allow a constraint @code{symbol} or @code{index_name}

to be specified. @xref{InnoDB}.

The syntax for other table types is provided only for compatibility,

to make it easier to port code from other SQL servers and to run applications

that create tables with references.

@xref{Differences from ANSI}.

* Table and index::             Table and Index Structures

* File space management::       File Space Management and Disk I/O

* Error handling::              Error Handling

* InnoDB change history::       InnoDB Change History

* InnoDB restrictions::         Restrictions on InnoDB Tables

* InnoDB contact information::  InnoDB Contact Information.

@end menu

algorithm of InnoDB guarantees that fragmentation in the index will

not occur.

@node Error handling, InnoDB restrictions, File space management, InnoDB

@subsection Error Handling

@end itemize

@node InnoDB restrictions, InnoDB contact information, Error handling, InnoDB

@node InnoDB restrictions, InnoDB change history, Error handling, InnoDB

@subsection Restrictions on InnoDB Tables

@itemize @bullet

the maximum size for a table. The minimum tablespace size is 10 MB.

@end itemize

@node InnoDB change history, InnoDB contact information, InnoDB restrictions, InnoDB

@subsection InnoDB Change History

@subsubsection MySQL/InnoDB-3.23.53, October xx, 2002

@itemize bullet

@item

We again use unbuffered disk i/o in Windows. Win XP and Win 2000

read performance seems to be very poor with normal i/o.

@item

Allow dropping and creating a table even if

innodb_force_recovery is set. One can use this to drop

a table which would cause a crash in rollback or purge,

or if a failed table import causes a runaway rollback in recovery.

@item

Fixed a bug: fast shutdown (which is the default) sometimes

was slowed down by purge and insert buffer merge.

@item

Fixed a bug: doing a big SELECT from a table where

no rows were visible in a consistent read could cause

a very long (> 600 seconds) semaphore wait in btr0cur.c line 310.

@end itemize

@subsubsection MySQL/InnoDB-4.0.4, October 2, 2002

@itemize bullet

@item

We again use unbuffered disk i/o in Windows. Win XP and Win 2000

read performance seems to be very poor with normal i/o.

@item

Increased the max key length of InnoDB tables from 500 to 1024 bytes.

@item

Increased the table comment field in SHOW TABLE STATUS so that

up to 16000 characters of foreign key definitions can be printed there.

@item

The auto-increment counter is no longer incremented if

an insert of a row immediately fails in an error.

@item

Allow dropping and creating a table even if

innodb_force_recovery is set. One can use this to drop

a table which would cause a crash in rollback or purge,

or if a failed table import causes a runaway rollback in recovery.

@item

Fixed a bug: Using ORDER BY primarykey DESC in 4.0.3 causes

an assertion failure in btr0pcur.c, line 203.

@item

Fixed a bug: fast shutdown (which is the default) sometimes

was slowed down by purge and insert buffer merge.

@item

Fixed a bug: doing a big SELECT from a table where

no rows were visible in a consistent read could cause

a very long (> 600 seconds) semaphore wait in btr0cur.c line 310.

@item

Fixed a bug: if the MySQL query cache was used, it did not get

invalidated by a modification done by ON DELETE CASCADE or ...SET NULL.

@item

Fixed a bug: if you created a temporary table inside LOCK TABLES,

and used that temporary table, that caused an assertion failure

in ha_innodb.cc.

@item

Fixed a bug: if you set innodb_flush_log_at_trx_commit to 1, SHOW

VARIABLES would show its value as 16 million.

@end itemize

@subsubsection MySQL/InnoDB-4.0.3, August 28, 2002

@itemize bullet

@item

Removed unnecessary deadlocks when inserts have to wait for

a locking read, update, or delete to release its next-key lock.

@item

The MySQL HANDLER SQL commands now work also for InnoDB type tables.

InnoDB does the HANDLER reads always as consistent reads.

HANDLER is a direct access path to read individual indexes of tables.

In some cases HANDLER can be used as a substitute of server-side cursors.

@item

Fixed a bug in 4.0.2: even a simple insert could crash the

AIX version.

@item

Fixed a bug: if you used in a table name characters whose code is > 127,

in DROP TABLE InnoDB could assert on line 155 of pars0sym.c.

@item

Compilation from source now provides a working version both on

HP-UX-11 and HP-UX-10.20. The source of 4.0.2 worked only on 11,

and the source of 3.23.52 only on 10.20.

@item

Fixed a bug: if compiled on 64-bit Solaris, InnoDB produced a bus error

at startup.

@end itemize

@subsubsection MySQL/InnoDB-3.23.52, August 16, 2002

@itemize bullet

@item

The feature set of 3.23 will be frozen from this version on. New features

will go the the 4.0 branch, and only bug fixes will be made to the 3.23

branch.

@item

Many CPU-bound join queries now run faster. On Windows also many

other CPU-bound queries run faster.

@item

A new SQL command SHOW INNODB STATUS returns the output of the

InnoDB Monitor to the client. The InnoDB Monitor now prints detailed info on

the latest detected deadlock.

@item

InnoDB made the SQL query optimizer to avoid too much index-only

range scans and choose full table scans instead. This is now fixed.

@item

"BEGIN" and "COMMIT" are now added in the binlog around transactions.

The MySQL replication now respects transaction borders:

a user will no longer see half transactions in replication slaves.

@item

A replication slave now prints in crash recovery the last

master binlog position it was able to recover to.

@item

A new setting innodb_flush_log_at_trx_commit=2 makes InnoDB to write

the log to the operating system file cache at each commit. This is

almost as fast as the setting innodb_flush_log_at_trx_commit=0, and

the setting 2 also has the nice feature that in a crash where the

operating system does not crash, no committed transaction is lost.

If the operating system crashes or there is a power outage, then

the setting 2 is no safer than the setting 0.

@item

Added checksum fields to log blocks.

@item

SET FOREIGN_KEY_CHECKS=0 helps in importing tables

in an arbitrary order which does not respect the foreign key rules.

@item

SET UNIQUE_CHECKS=0 speeds up table imports into InnoDB

if you have UNIQUE constraints on secondary indexes.

@item

SHOW TABLE STATUS now lists also possible ON DELETE CASCADE or

ON DELETE SET NULL in the comment field of the table.

@item

When CHECK TABLE is run on any InnoDB type table, it now

checks also the adaptive hash index for all tables.

@item

If you defined ON DELETE CASCADE or SET NULL and updated the

referenced key in the parent row, InnoDB deleted or updated

the child row. This is now changed to conform to SQL-92: you get

the error 'Cannot delete parent row'.

@item

Improved the auto-increment algorithm: now the first insert or

SHOW TABLE STATUS initializes the auto-inc counter for the table.

This removes almost all surprising deadlocks caused by

SHOW TABLE STATUS.

@item

Aligned some buffers used in reading and writing to data files.

This allows using unbuffered raw devices as data files in Linux.

@item

Fixed a bug: If you updated the primary key of a table so that only the

case of characters changed, that could cause assertion

failures, mostly in page0page.ic line 515.

@item

Fixed a bug: If you delete or update a row referenced in a foreign key

constraint and the foreign key check has to wait for a lock,

then the check may report an erroneous result. This

affects also the ON DELETE... operation.

@item

Fixed a bug: A deadlock or a lock wait timeout error in InnoDB

causes InnoDB to roll back the whole transaction, but MySQL could still

write the earlier SQL statements to the binlog, even though

InnoDB rolled them back. This could, for example, cause replicated

databases to get out-of-sync.

@item

Fixed a bug: If the database happened to crash in the middle of a

commit, then the recovery might leak tablespace pages.

@item

Fixed a bug: If you specified a non-latin1 character set in my.cnf,

then, in contrary to what is stated in the manual, in a foreign key

constraint a string type column had to have the same length specification

in the referencing table and the referenced table.

@item

Fixed a bug: DROP TABLE or DROP DATABASE could fail if there

simultaneously was a CREATE TABLE running.

@item

Fixed a bug: If you configured the buffer pool bigger than 2 GB in

a 32-bit computer, InnoDB would assert in buf0buf.ic line 214.

@item

Fixed a bug: on 64-bit computers updating rows which contained the

SQL NULL in some column could cause the undo log and the ordinary

log to become corrupt.

@item

Fixed a bug: innodb_log_monitor caused a hang if it suppressed

lock prints for a page.

@item

Fixed a bug: in the HP-UX-10.20 version mutexes would leak and cause

race conditions and crashes in any part of InnoDB code.

@item

Fixed a bug: if you ran in the AUTOCOMMIT mode, executed a SELECT,

and immediately after that a RENAME TABLE, then RENAME would fail and

MySQL would complain about error 1192.

@item

Fixed a bug: if compiled on 64-bit Solaris, InnoDB produced a bus error

at startup.

@end itemize

@subsubsection MySQL/InnoDB-4.0.2, July 10, 2002

@itemize bullet

@item

InnoDB is essentially the same as InnoDB-3.23.51.

@item

If no innodb_data_file_path is specified, InnoDB at the database creation

now creates a 10 MB auto-extending data file ibdata1 to the datadir

of MySQL. In 4.0.1 the file was 64 MB and not auto-extending.

@end itemize

@subsubsection MySQL/InnoDB-3.23.51, June 12, 2002

@itemize bullet

@item

Fixed a bug: a join could result in a seg fault in copying of a BLOB or

TEXT column if some of the BLOB or TEXT columns in the table contained

SQL NULL values.

@item

Fixed a bug: if you added self-referential foreign key constraints with

ON DELETE CASCADE to tables and a row deletion caused InnoDB

to attempt the deletion of the same row twice because of

a cascading delete, then you got an assertion failure.

@item

Fixed a bug: if you use MySQL 'user level locks' and close

a connection, then InnoDB may assert in ha_innobase.cc, line 302.

@end itemize

@subsubsection MySQL/InnoDB-3.23.50, April 23, 2002

@itemize bullet

@item

InnoDB now supports an auto-extending last data file. You do not need

to preallocate the whole data file at the database startup.

@item

Made several changes to facilitate the use of the InnoDB Hot Backup

tool. It is a separate non-free tool you can use to take online backups

of your database without shutting down the server or setting

any locks.

@item

If you want to run the InnoDB Hot Backup tool on an auto-extending

data file you have to upgrade it to version ibbackup-0.35.

@item

The log scan phase in crash recovery will now run much faster.

@item

Starting from this server version, the hot backup tool

truncates unused ends in the backup InnoDB data files.

@item

To allow the hot backup tool to work, on Windows we no longer use

unbuffered i/o or native async i/o; instead we use the same simulated

async i/o as on Unix.

@item

You can now define the ON DELETE CASCADE or ON DELETE SET NULL

clause on foreign keys.

@item

FOREIGN KEY constraints now survive ALTER TABLE and CREATE

INDEX.

@item

We suppress the FOREIGN KEY check if any of the column values in the

foreign key or referenced key to be checked is the SQL NULL. This

is compatible with Oracle, for example.

@item

SHOW CREATE TABLE now lists also foreign key constraints. Also

mysqldump no longer forgets about foreign keys in table definitions.

@item

You can now add a new foreign key constraint with

ALTER TABLE ... ADD CONSTRAINT FOREIGN KEY (...) REFERENCES ... (...).

@item

FOREIGN KEY definitions now allow backquotes around table and

column names.

@item

MySQL command

SET TRANSACTION ISOLATION LEVEL ...

has now the following effect on

InnoDB tables: if a transaction is defined as SERIALIZABLE

then InnoDB conceptually adds LOCK IN SHARE MODE

to all consistent reads. If a transaction is defined to have any other

isolation level, then InnoDB obeys its default locking strategy

which is REPEATABLE READ.

@item

SHOW TABLE STATUS no longer sets an x-lock at the end of an

auto-increment index if the auto-increment counter has already

been initialized. This removes in almost all cases the surprising deadlocks

caused by SHOW TABLE STATUS.

@item

Fixed a bug: in a CREATE TABLE statement the string 'foreign'

followed by a non-space character confused the FOREIGN KEY parser

and caused table creation to fail with errno 150.

@end itemize

@subsubsection MySQL/InnoDB-3.23.49, February 17, 2002

@itemize bullet

@item

Fixed a bug: if you called DROP DATABASE for a database on which

there simultaneously were running queries, the MySQL server could crash

or hang. Crashes fixed, but a full fix has to wait some changes

in the MySQL layer of code.

@item

Fixed a bug: on Windows one had to put the database name

in lower case for DROP

DATABASE to work. Fixed in 3.23.49: case no longer matters

on Windows. On Unix the database name remains case-sensitive.

@item

Fixed a bug: if one defined a non-latin1 character set as

the default character set,

then definition of foreign key constraints could fail

in an assertion failure

in dict0crea.c, reporting an internal error 17.

@end itemize

@subsubsection MySQL/InnoDB-3.23.48, February 9, 2002

@itemize bullet

@item

Tuned the SQL optimizer to favor more often index searches

over table scans.

@item

Fixed a performance problem when several large SELECT

queries are run concurrently on a multiprocessor Linux computer.

Large CPU-bound SELECT queries will now also generally run faster on

all platforms.

@item

If MySQL binlogging is used,

InnoDB now prints after crash recovery the latest MySQL binlog

file name and the position in that file (= byte offset)

InnoDB was able to recover to. This is useful, for example,

when resynchronizing a master and a slave database in replication.

@item

Added better error messages to help in installation problems.

@item

One can now recover also MySQL temporary tables which have become

orphaned inside the InnoDB tablespace.

@item

InnoDB now prevents a FOREIGN KEY declaration where the signedness

is not the same in the referencing and referenced integer columns.

@item

Fixed a bug: calling SHOW CREATE TABLE or SHOW TABLE STATUS

could cause memory corruption and make mysqld to crash.

Especially at risk was mysqldump, because it calls frequently

SHOW CREATE TABLE.

@item

Fixed a bug: if on Unix you did an ALTER TABLE to an InnoDB table and

simultaneously did queries to it, mysqld could crash with an assertion

failure in row0row.c, line 474.

@item

Fixed a bug: if inserts to several tables containing an auto-inc column

were wrapped inside one LOCK TABLES, InnoDB asserted in lock0lock.c.

@item

In 3.23.47 we allowed several NULLS in a UNIQUE secondary index.

But CHECK TABLE was not relaxed: it reports the table as corrupt.

CHECK TABLE no longer complains in this situation.

@item

Fixed a bug: on Sparc and other high-endian processors SHOW VARIABLES

showed innodb_flush_log_at_trx_commit and other boolean-valued

startup parameters always OFF even if they were switched on. 

@item

Fixed a bug: if you ran mysqld-max-nt as a service on Windows NT/2000,

the service shutdown did not always wait long enough for the InnoDB shutdown

to finish.

@end itemize

@subsubsection MySQL/InnoDB-3.23.47, December 28, 2001

@itemize bullet

@item

Recovery happens now faster, especially in a lightly loaded system,

because background checkpointing has been made more frequent.

@item

InnoDB allows now several similar key values in a UNIQUE secondary index

if those values contain SQL NULLs. Thus the convention is now the same as in

MyISAM tables.

@item

InnoDB gives a better row count estimate for a table which contains BLOBs.

@item

In a FOREIGN KEY constraint InnoDB is now case-insensitive to column

names, and in Windows also to table names.

@item

InnoDB allows a FOREIGN KEY column of CHAR type to refer to a column of

VARCHAR type, and vice versa. MySQL silently changes the type of some

columns between CHAR and VARCHAR, and these silent changes do not hinder

FOREIGN KEY declaration any more.

@item

Recovery has been made more resilient to corruption of log files.

@item

Unnecessary statistics calculation has been removed from queries which

generate a temporary table. Some ORDER BY and DISTINCT queries will now run

much faster.

@item

MySQL now knows that the table scan of an InnoDB table is done through the

primary key. This will save a sort in some ORDER BY queries.

@item

The maximum key length of InnoDB tables is again restricted to 500 bytes.

The MySQL interpreter is not able to handle longer keys.

@item

The default value of innodb_lock_wait_timeout was changed from infinite to

50 seconds, the default value of innodb_file_io_threads from 9

to 4.

@end itemize

@subsubsection MySQL/InnoDB-4.0.1, December 23, 2001

@itemize bullet

@item

InnoDB is the same as in 3.23.47.

@item

In 4.0.0 the MySQL interpreter did not know the syntax LOCK IN

SHARE MODE. This has been fixed.

@item

In 4.0.0 multi-table delete did not work for transactional tables.

This has been fixed.

@end itemize

@subsubsection MySQL/InnoDB-3.23.46, November 30, 2001

@itemize bullet

@item

This is the same as 3.23.45.

@end itemize

@subsubsection MySQL/InnoDB-3.23.45, November 23, 2001

@itemize bullet

@item

This is a bugfix release.

@item

In versions 3.23.42-.44 when creating a table on Windows you

have to use lower case letters in the database name to be able to

access the table. Fixed in 3.23.45.

@item

InnoDB now flushes stdout and stderr every 10 seconds: if these

are redirected to files, the file contents can be better viewed with

an editor.

@item

Fixed an assertion failure in .44, in trx0trx.c, line 178

when you drop a table which has

the .frm file but does not exist inside InnoDB.

@item

Fixed a bug in the insert buffer.

The insert buffer tree could get into an inconsistent state, causing a crash,

and also crashing the recovery. This bug could appear especially in

large table imports or alterations.

@item

Fixed a bug in recovery: InnoDB could go into an infinite loop

constantly printing

a warning message that it cannot find free blocks from the buffer pool.

@item

Fixed a bug: when you created a temporary table of the InnoDB type, and then

used ALTER TABLE to it, the MySQL server could crash.

@item

Prevented creation of MySQL system tables 'mysql.user',

'mysql.host', or 'mysql.db', in the

InnoDB type.

@item

Fixed a bug which can cause an assertion failure in 3.23.44 in

srv0srv.c, line 1728.

@end itemize

@subsubsection MySQL/InnoDB-3.23.44, November 2, 2001

@itemize bullet

@item

You can define foreign key constraints on InnoDB

tables. An example: FOREIGN KEY (col1) REFERENCES table2(col2).

@item

You can create > 4 GB data files in those

file systems that allow it.

@item

Improved InnoDB monitors, including a new innodb_table_monitor

which allows you to print the contents of the InnoDB internal data

dictionary.

@item

DROP DATABASE will now work also for InnoDB tables.

@item

Accent characters in the default character set

latin1 will be ordered according to the MySQL ordering.<br>

NOTE: if you are using latin1 and have inserted characters

whose code is > 127 to an indexed CHAR column, you should run

CHECK TABLE on your table when you upgrade to

3.23.43, and drop and reimport the table if CHECK TABLE

reports an error!

@item

InnoDB will calculate better table cardinality

estimates.

@item

Change in deadlock resolution:

in .43 a deadlock rolls back only the

SQL statement, in .44 it will roll back the whole transaction.

@item

Deadlock, lock wait timeout, and foreign key

constraint violations (no parent row, child rows exist)

now return native MySQL

error codes 1213, 1205, 1216, 1217, respectively.

@item

A new my.cnf parameter innodb_thread_concurrency

helps in performance tuning in high concurrency environments.

@item

A new my.cnf option innodb_force_recovery will

help you in dumping tables from a corrupted database.

@item

A new my.cnf option innodb_fast_shutdown will

speed up shutdown. Normally InnoDB does a full purge

and an insert buffer merge at shutdown.

@item

Raised maximum key length to 7000 bytes from a

previous limit of 500 bytes.

@item

Fixed a bug in replication of auto-inc columns with multiline inserts.

@item

Fixed a bug when the case of letters changes in an update of an indexed

secondary column.

@item

Fixed a hang when there are > 24 data files.

@item

Fixed a crash when MAX(col) is selected from an empty table, and col is a

not the first column in a multi-column index.

@item

Fixed a bug in purge which could cause crashes.

@end itemize

@subsubsection MySQL/InnoDB-3.23.43, October 4, 2001

@itemize bullet

@item

This is essentially the same as InnoDB-3.23.42.

@end itemize

@subsubsection MySQL/InnoDB-3.23.42, September 9, 2001

@itemize bullet

@item

Fixed a bug which corrupted the table if the primary key

of a > 8000-byte row was updated.

@item

There are now 3 types of InnoDB Monitors: innodb_monitor,

innodb_lock_monitor, and innodb_tablespace_monitor.

innodb_monitor now prints also buffer pool hit rate and the total

number of rows inserted, updated, deleted, read.

@item

Fixed a bug in RENAME TABLE.

@item

Fixed a bug in replication with an auto-increment column.

@end itemize

@subsubsection MySQL/InnoDB-3.23.41, August 13, 2001

@itemize bullet

@item

Support for < 4 GB rows. The previous limit was

8000 bytes.

@item

Use the doublewrite file flush method.

@item

Raw disk partitions supported as data files.

@item

InnoDB Monitor.

@item

Several hang bugs fixed and an ORDER BY

bug ('Sort aborted') fixed.

@end itemize

@subsubsection MySQL/InnoDB-3.23.40, July 16, 2001

@itemize bullet

@item

Only a few rare bugs fixed.

@end itemize

@subsubsection MySQL/InnoDB-3.23.39, June 13, 2001

@itemize bullet

@item

CHECK TABLE now works for InnoDB tables.

@item

A new my.cnf parameter innodb_unix_file_flush_method

introduced. It can be used to tune disk write performance.

@item

An auto-increment column now gets new values past the

transaction mechanism. This saves CPU time and eliminates

transaction deadlocks in new value assignment.

@item

Several bug fixes, most notably the rollback bug in 3.23.38.

@end itemize

@subsubsection MySQL/InnoDB-3.23.38, May 12, 2001

@itemize bullet

@item

The new syntax SELECT ... LOCK IN SHARE MODE is introduced.

@item

InnoDB now calls fsync after every disk write and calculates

a checksum

for every database page it writes or reads, which will reveal disk defects.

@item

Several bug fixes.

@end itemize

@node InnoDB contact information,  , InnoDB restrictions, InnoDB

@node InnoDB contact information,  , InnoDB change history, InnoDB

@subsection InnoDB Contact Information

Contact information of Innobase Oy, producer of the InnoDB engine.