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py-mysql2pgsql

Tool for migrating/converting from mysql to postgresql.

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========================================================================================

py-mysql2pgsql - A tool for migrating/converting/exporting data from MySQL to PostgreSQL

This tool allows you to take data from an MySQL server (only tested on 5.x) and write a PostgresSQL compatible (8.2 or higher) dump file or pipe it directly into your running PostgreSQL server (8.2 or higher).

.. attention:: Currently there is no support for importing spatial data from MySQL <http://dev.mysql.com/doc/refman/5.5/en/spatial-extensions.html>_.

Installation:

If you're like me you don't like random stuff polluting your python install. Might I suggest installing this in an virtualenv?

::

> virtualenv --no-site-packages ~/envs/py-mysql2pgsql
> source ~/envs/py-mysql2pgsql/bin/activate

Requirements:

  • Python 2.7 <http://www.python.org/getit/>_
  • MySQL-python <http://pypi.python.org/pypi/MySQL-python>_
  • psycopg2 <http://pypi.python.org/pypi/psycopg2>_
  • PyYAML <http://pypi.python.org/pypi/PyYAML>_
  • termcolor <http://pypi.python.org/pypi/termcolor>_ (unless you're installing on windows)
  • pytz <http://pypi.python.org/pypi/pytz>_

On Windows

I have only done limited testing on this platform using Python 2.7. Here are the driver dependencies for windows, install these before attempting to install py-mysql2pgsql or it will fail.

  • psycopg2 for Windows <http://www.stickpeople.com/projects/python/win-psycopg/>_
  • MySQL-python for Windows <http://www.codegood.com/archives/129>_

From PyPI:

All dependencies should be automatically installed when installing the app the following ways

::

> pip install py-mysql2pgsql

From source:

::

> git clone git://github.com/philipsoutham/py-mysql2pgsql.git
> cd py-mysql2pgsql
> python setup.py install

Usage:

Looking for help?

::

> py-mysql2pgsql -h
usage: py-mysql2pgsql [-h] [-v] [-f FILE]

Tool for migrating/converting data from mysql to postgresql.

optional arguments:
  -h, --help            show this help message and exit
  -v, --verbose         Show progress of data migration.
  -f FILE, --file FILE  Location of configuration file (default:
                        mysql2pgsql.yml). If none exists at that path,
                        one will be created for you.

Don't worry if this is your first time, it'll be gentle.

::

> py-mysql2pgsql
No configuration file found.
A new file has been initialized at: mysql2pgsql.yml
Please review the configuration and retry...

As the output suggests, a file was created at mysql2pgsql.yml for you to edit. For the impatient, here is what the file contains.

::

# a socket connection will be selected if a 'socket' is specified
# also 'localhost' is a special 'hostname' for MySQL that overrides the 'port' option
# and forces it to use a local socket connection
# if tcp is chosen, you can use compression

mysql:
 hostname: localhost
 port: 3306
 socket: /tmp/mysql.sock
 username: mysql2psql
 password: 
 database: mysql2psql_test
 compress: false
destination:
 # if file is given, output goes to file, else postgres
 file: 
 postgres:
  hostname: localhost
  port: 5432
  username: mysql2psql
  password: 
  database: mysql2psql_test

# if only_tables is given, only the listed tables will be converted.  leave empty to convert all tables.
#only_tables:
#- table1
#- table2
# if exclude_tables is given, exclude the listed tables from the conversion.
#exclude_tables:
#- table3
#- table4

# if supress_data is true, only the schema definition will be exported/migrated, and not the data
supress_data: false

# if supress_ddl is true, only the data will be exported/imported, and not the schema
supress_ddl: false

# if force_truncate is true, forces a table truncate before table loading
force_truncate: false

# if timezone is true, forces to append/convert to UTC tzinfo mysql data
timezone: false

# if index_prefix is given, indexes will be created whith a name prefixed with index_prefix
index_prefix:

Pretty self explanatory right? A couple things to note, first if destination -> file is populated all output will be dumped to the specified location regardless of what is contained in destination -> postgres. So if you want to dump directly to your server make sure the file value is blank.

Say you have a MySQL db with many, many tables, but you're only interested in exporting a subset of those table, no problem. Add only the tables you want to include in only_tables or tables that you don't want exported to exclude_tables.

Other items of interest may be to skip moving the data and just create the schema or vice versa. To skip the data and only create the schema set supress_data to true. To migrate only data and not recreate the tables set supress_ddl to true; if there's existing data that you want to drop before importing set force_truncate to true. force_truncate is not necessary when supress_ddl is set to false.

Note that when migrating, it's sometimes possible to knock your sequences out of whack. When this happens, you may get IntegrityErrors about your primary keys saying things like, "duplicate key value violates unique constraint." See this page <https://wiki.postgresql.org/wiki/Fixing_Sequences>_ for a fix

Due to different naming conventions in mysql an postgresql, there is a chance that the tool generates index names that collide with table names. This can be circumvented by setting index_prefix.

One last thing, the --verbose flag. Without it the tool will just go on it's merry way without bothering you with any output until it's done. With it you'll get a play-by-play summary of what's going on. Here's an example.

::

> py-mysql2pgsql -v -f mysql2pgsql.yml
START PROCESSING table_one
  START  - CREATING TABLE table_one
  FINISH - CREATING TABLE table_one
  START  - WRITING DATA TO table_one
  24812.02 rows/sec [20000]  
  FINISH - WRITING DATA TO table_one
  START  - ADDING INDEXES TO table_one
  FINISH - ADDING INDEXES TO table_one
  START  - ADDING CONSTRAINTS ON table_one
  FINISH - ADDING CONSTRAINTS ON table_one
FINISHED PROCESSING table_one

START PROCESSING table_two
  START  - CREATING TABLE table_two
  FINISH - CREATING TABLE table_two
  START  - WRITING DATA TO table_two

  FINISH - WRITING DATA TO table_two
  START  - ADDING INDEXES TO table_two
  FINISH - ADDING INDEXES TO table_two
  START  - ADDING CONSTRAINTS ON table_two
  FINISH - ADDING CONSTRAINTS ON table_two
FINISHED PROCESSING table_two

Data Type Conversion Legend

Since there is not a one-to-one mapping between MySQL and PostgreSQL data types, listed below are the conversions that are applied. I've taken some liberties with some, others should come as no surprise.

==================== =========================================== MySQL PostgreSQL ==================== =========================================== char character varchar character varying tinytext text mediumtext text text text longtext text tinyblob bytea mediumblob bytea blob bytea longblob bytea binary bytea varbinary bytea bit bit varying tinyint smallint tinyint unsigned smallint smallint smallint smallint unsigned integer mediumint integer mediumint unsigned integer int integer int unsigned bigint bigint bigint bigint unsigned numeric float real float unsigned real double double precision double unsigned double precision decimal numeric decimal unsigned numeric numeric numeric numeric unsigned numeric date date datetime timestamp without time zone time time without time zone timestamp timestamp without time zone year smallint enum character varying (with check constraint) set ARRAY[]::text[] ==================== ===========================================

Conversion caveats:

Not just any valid MySQL database schema can be simply converted to the PostgreSQL. So when you end with a different database schema please note that:

  • Most MySQL versions don't enforce NOT NULL constraint on date and enum fields. Because of that NOT NULL is skipped for this types. Here's an excuse for the dates: <http://bugs.mysql.com/bug.php?id=59526>_.

About:

I ported much of this from an existing project written in Ruby by Max Lapshin over at <https://github.com/maxlapshin/mysql2postgres>_. I found that it worked fine for most things, but for migrating large tables with millions of rows it started to break down. This motivated me to write py-mysql2pgsql which uses a server side cursor, so there is no "paging" which means there is no slow down while working it's way through a large dataset.

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