mysqldiff - Online in the Cloud

PROGRAM:

NAME

mysqldiff - Identify Differences Among Database Objects

SYNOPSIS

mysqldiff [options] {db1[:db1] | {db1.obj1[:db2.obj2]} ...

DESCRIPTION

This utility reads the definitions of objects and compares them using a diff-like method
to determine whether they are the same. The utility displays the differences for objects
that are not the same.

Use the notation db1:db2 to name two databases to compare, or, alternatively just db1 to
compare two databases with the same name. The latter case is a convenience notation for
comparing same-named databases on different servers.

The comparison may be run against two databases of different names on a single server by
specifying only the --server1 option. The user can also connect to another server by
specifying the --server2 option. In this case, db1 is taken from server1 and db2 from
server2.

When a database pair is specified, all objects in one database are compared to the
corresponding objects in the other. Any objects not appearing in either database produce
an error.

To compare a specific pair of objects, add an object name to each database name in db.obj
format. For example, use db1.obj1:db2.obj2 to compare two named objects, or db1.obj1 to
compare an object with the same name in databases with the same name. It is not legal to
mix a database name with an object name. For example, db1.obj1:db2 and db1:db2.obj2 are
illegal.

The comparison may be run against a single server for comparing two databases of different
names on the same server by specifying only the --server1 option. Alternatively, you can
also connect to another server by specifying the --server2 option. In this case, the first
object to compare is taken from server1 and the second from server2.

By default, the utility generates object differences as a difference report. However, you
can generate a transformation report containing SQL statements for transforming the
objects for conformity instead. Use the 'sql' value for the --difftype option to produce a
listing that contains the appropriate ALTER commands to conform the object definitions for
the object pairs specified. If a transformation cannot be formed, the utility reports the
diff of the object along with a warning statement. See important limitations in the NOTES
section.

To specify how to display diff-style output, use one of the following values with the
--difftype option:

· unified (default)

Display unified format output.

· context

Display context format output.

· differ

Display differ-style format output.

· sql

Display SQL transformation statement output.

The --changes-for option controls the direction of the difference (by specifying the
object to be transformed) in either the difference report (default) or the transformation
report (designated with the --difftype=sql option). Consider the following command:

mysqldiff --server1=root@host1 --server2=root@host2 --difftype=sql
db1.table1:dbx.table3

The leftmost database (db1) exists on the server designated by the --server1 option
(host1). The rightmost database (dbx) exists on the server designated by the --server2
option (host2).

· --changes-for=server1: Produce output that shows how to make the definitions of
objects on server1 like the definitions of the corresponding objects on server2.

· --changes-for=server2: Produce output that shows how to make the definitions of
objects on server2 like the definitions of the corresponding objects on server1.

The default direction is server1.

For sql difference format, you can also see the reverse transformation by specifying the
--show-reverse option.

The utility stops on the first occurrence of missing objects or when an object does not
match. To override this behavior, specify the --force option to cause the utility to
attempt to compare all objects listed as arguments.
OPTIONS

mysqldiff accepts the following command-line options:

· --help

Display a help message and exit.

· --changes-for=<direction>

Specify the server to show transformations to match the other server. For example, to
see the transformation for transforming object definitions on server1 to match the
corresponding definitions on server2, use --changes-for=server1. Permitted values are
server1 and server2. The default is server1.

· --difftype=<difftype>, -d<difftype>

Specify the difference display format. Permitted format values are unified, context,
differ, and sql. The default is unified.

· --force

Do not halt at the first difference found. Process all objects to find all
differences.

· --quiet, -q

Do not print anything. Return only an exit code of success or failure.

· --server1=<source>

Connection information for the first server in the format:
<user>[:<passwd>]@<host>[:<port>][:<socket>] or <login-path>[:<port>][:<socket>].

· --server2=<source>

Connection information for the second server in the format:
<user>[:<passwd>]@<host>[:<port>][:<socket>] or <login-path>[:<port>][:<socket>].

· --show-reverse

Produce a transformation report containing the SQL statements to conform the object
definitions specified in reverse. For example, if --changes-for is set to server1,
also generate the transformation for server2. Note: The reverse changes are annotated
and marked as comments.

· --verbose, -v

Specify how much information to display. Use this option multiple times to increase
the amount of information. For example, -v = verbose, -vv = more verbose, -vvv =
debug.

· --version

Display version information and exit.

· --width=<number>

Change the display width of the test report. The default is 75 characters.
NOTES

You must provide connection parameters (user, host, password, and so forth) for an account
that has the appropriate privileges to access all objects to be compared.

The SQL transformation feature has these known limitations:

· When tables with partition differences are encountered, the utility generates the
ALTER TABLE statement for all other changes but prints a warning and omits the
partition differences.

· If the transformation detects table options in the source table (specified with the
--changes-for option) that are not changed or do not exist in the target table, the
utility generates the ALTER TABLE statement for all other changes but prints a warning
and omits the table option differences.

· Rename for events is not supported. This is because mysqldiff compares objects by
name. In this case, depending on the direction of the diff, the event is identified as
needing to be added or a DROP EVENT statement is generated.

· Changes in the definer clause for events are not supported.

· SQL extensions specific to MySQL Cluster are not supported.

For the --difftype option, the permitted values are not case sensitive. In addition,
values may be specified as any unambiguous prefix of a valid value. For example,
--difftype=d specifies the differ type. An error occurs if a prefix matches more than one
valid value.

The path to the MySQL client tools should be included in the PATH environment variable in
order to use the authentication mechanism with login-paths. This will allow the utility to
use the my_print_defaults tools which is required to read the login-path values from the
login configuration file (.mylogin.cnf).

If any database object identifier specified as an argument contains special characters or
is a reserved word, then it must be appropriately quoted with backticks (`). In turn,
names quoted with backticks must also be quoted with single or double quotes depending on
the operating system, i.e. (") in Windows or (') in non-Windows systems, in order for the
utilities to read backtick quoted identifiers as a single argument. For example, to show
the difference between table weird`table1 from database weird`db.name and table
weird`table2 from database other:weird`db.name, the objects pair must be specified using
the following syntax (in non-Windows):
'`weird``db.name`.`weird``table1`:`other:weird``db.name`.`weird``table2`'.
EXAMPLES

To compare the employees and emp databases on the local server, use this command:

$ mysqldiff --server1=root@localhost employees:emp1
# server1 on localhost: ... connected.
WARNING: Objects in server1:employees but not in server2:emp1:
EVENT: e1
Compare failed. One or more differences found.
$ mysqldiff --server1=root@localhost
employees.t1:emp1.t1 employees.t3:emp1.t3
# server1 on localhost: ... connected.
# Comparing employees.t1 to emp1.t1 [PASS]
# server1 on localhost: ... connected.
# Comparing employees.t3 to emp1.t3 [PASS]
Success. All objects are the same.
$ mysqldiff --server1=root@localhost
employees.salaries:emp1.salaries --differ
# server1 on localhost: ... connected.
# Comparing employees.salaries to emp1.salaries [FAIL]
# Object definitions are not the same:
CREATE TABLE `salaries` (
`emp_no` int(11) NOT NULL,
`salary` int(11) NOT NULL,
`from_date` date NOT NULL,
`to_date` date NOT NULL,
PRIMARY KEY (`emp_no`,`from_date`),
KEY `emp_no` (`emp_no`)
- ) ENGINE=InnoDB DEFAULT CHARSET=latin1
? ^^^^^
+ ) ENGINE=MyISAM DEFAULT CHARSET=latin1
? ++ ^^^
Compare failed. One or more differences found.

The following examples show how to generate a transformation report. Assume the following
object definitions:

Host1:

CREATE TABLE db1.table1 (num int, misc char(30));

Host2:

CREATE TABLE dbx.table3 (num int, notes char(30), misc char(55));

To generate a set of SQL statements that transform the definition of db1.table1 to
dbx.table3, use this command:

$ mysqldiff --server1=root@host1 --server2=root@host2
--changes-for=server1 --difftype=sql
db1.table1:dbx.table3
# server1 on host1: ... connected.
# server2 on host2: ... connected.
# Comparing db1.table1 to dbx.table3 [FAIL]
# Transformation statements:
ALTER TABLE db1.table1
ADD COLUMN notes char(30) AFTER a,
CHANGE COLUMN misc misc char(55);
Compare failed. One or more differences found.

To generate a set of SQL statements that transform the definition of dbx.table3 to
db1.table1, use this command:

$ mysqldiff --server1=root@host1 --server2=root@host2
--changes-for=server2 --difftype=sql
db1.table1:dbx.table3
# server1 on host1: ... connected.
# server2 on host2: ... connected.
# Comparing db1.table1 to dbx.table3 [FAIL]
# Transformation statements:
ALTER TABLE dbx.table3
DROP COLUMN notes,
CHANGE COLUMN misc misc char(30);
Compare failed. One or more differences found.

To generate a set of SQL statements that transform the definitions of dbx.table3 and
db1.table1 in both directions, use this command:

$ mysqldiff --server1=root@host1 --server2=root@host2
--show-reverse --difftype=sql
db1.table1:dbx.table3
# server1 on host1: ... connected.
# server2 on host2: ... connected.
# Comparing db1.table1 to dbx.table3 [FAIL]
# Transformation statements:
# --destination=server1:
ALTER TABLE db1.table1
ADD COLUMN notes char(30) AFTER a,
CHANGE COLUMN misc misc char(55);
# --destination=server2:
# ALTER TABLE dbx.table3
# DROP COLUMN notes,
# CHANGE COLUMN misc misc char(30);
Compare failed. One or more differences found.

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