MySQL Foreign Data Wrapper for PostgreSQL
This PostgreSQL extension implements a Foreign Data Wrapper (FDW) for MySQL.
Please note that this version of mysql_fdw works with PostgreSQL and EDB Postgres Advanced Server 9.3, 9.4 and 9.5. Work is underway for certification with 9.6Beta.
To build on POSIX-compliant systems you need to ensure the
pg_configexecutable is in your path when you run
make. This executable is typically in your PostgreSQL installation's
bindirectory. For example:
$ export PATH=/usr/local/pgsql/bin/:$PATH
mysql_configmust also be in the path, it resides in the MySQL
$ export PATH=/usr/local/mysql/bin/:$PATH
Compile the code using make.
$ make USE_PGXS=1
Finally install the foreign data wrapper.
$ make USE_PGXS=1 install
Not that we have tested the
mysql_fdw extension only on MacOS and Ubuntu systems, but other *NIX's should also work.
The following enhancements are added to the latest version of
The previous version was only read-only, the latest version provides the write capability. The user can now issue insert/update and delete statements for the foreign tables using the mysql FDW. It uses the PG type casting mechanism to provide opposite type casting between mysql and PG data types.
The latest version comes with a connection pooler that utilises the same mysql database connection for all the queries in the same session. The previous version would open a new mysql database connection for every query. This is a performance enhancement.
Where clause push-down
The latest version will push-down the foreign table where clause to the foreign server. The where condition on the foreign table will be executed on the foreign server hence there will be fewer rows to to bring across to PostgreSQL. This is a performance feature.
The previous version was fetching all the columns from the target foreign table. The latest version does the column push-down and only brings back the columns that are part of the select target list. This is a performance feature.
select queries to use prepared statement)
select queries are now using prepared statements instead of simple query protocol.
The following parameters can be set on a MySQL foreign server object:
host: Address or hostname of the MySQL server. Defaults to
port: Port number of the MySQL server. Defaults to
secure_auth: Enable or disable secure authentication. Default is
trueThe following parameters can be set on a MySQL foreign table object:
dbname: Name of the MySQL database to query. This is a mandatory option.
table_name: Name of the MySQL table, default is the same as foreign table.
The following parameters need to supplied while creating user mapping.
username: Username to use when connecting to MySQL.
password: Password to authenticate to the MySQL server with.
-- load extension first time after install
CREATE EXTENSION mysql_fdw;
-- create server object
CREATE SERVER mysql_server FOREIGN DATA WRAPPER mysql_fdw OPTIONS (host '127.0.0.1', port '3306');
-- create user mapping
CREATE USER MAPPING FOR postgres SERVER mysql_server OPTIONS (username 'foo', password 'bar');
-- create foreign table
CREATE FOREIGN TABLE warehouse( warehouse_id int, warehouse_name text, warehouse_created datetime) SERVER mysql_server OPTIONS (dbname 'db', table_name 'warehouse');
-- insert new rows in table
INSERT INTO warehouse values (1, 'UPS', sysdate()); INSERT INTO warehouse values (2, 'TV', sysdate()); INSERT INTO warehouse values (3, 'Table', sysdate());
-- select from table
SELECT * FROM warehouse; warehouse_id | warehouse_name | warehouse_created --------------+----------------+-------------------- 1 | UPS | 29-SEP-14 23:33:46 2 | TV | 29-SEP-14 23:34:25 3 | Table | 29-SEP-14 23:33:49
-- delete row from table
DELETE FROM warehouse where warehouse_id = 3;
-- update a row of table
UPDATE warehouse set warehouse_name = 'UPS_NEW' where warehouse_id = 1;
-- explain a table
EXPLAIN SELECT warehouse_id, warehouse_name FROM warehouse WHERE warehouse_name LIKE 'TV' limit 1; QUERY PLAN Limit (cost=10.00..11.00 rows=1 width=36) -> Foreign Scan on warehouse (cost=10.00..13.00 rows=3 width=36) Local server startup cost: 10 Remote query: SELECT warehouse_id, warehouse_name FROM db.warehouse WHERE ((warehouse_name like 'TV'))
Planning time: 0.564 ms (5 rows)
If you experince any bug and have a fix for that, or have a new idea, create a ticket on github page Before creating a pull request please read the contributing guidlines.
This project will be modified to maintain compatibility with new PostgreSQL and EDB Postgres Advanced Server releases.
If you require commercial support, please contact the EnterpriseDB sales team, or check whether your existing PostgreSQL support provider can also support mysql_fdw.
The following features are added as part of this mysql_fdw release :
1) Support for PostgreSQL 9.5.
IMPORT FOREIGN SCHEMA support. Now mysql_fdw can use the import foreign schema functionality to import the remote server schema
metadata in PostgreSQL. (pull request #62)
3) DML support for binary data. Binary data (longblob) in MySQL can mapped to PostgreSQL's bytea datatype. (#66)
4) Support and map the MySQL datatype 'mediumblob' to BYTEA in PostgreSQL. (pull request #82)
5) Support for JSON data type. (#58)
6) Added MariaDB client library compatibility. (pull request #59)
7) Added init_command server option which is used as MYSQL_INIT_COMMAND and may be used as OPTION in CREATE SERVER statement.
8) Introduced new server option "use_remote_estimate". (#75)
A new foreign server option "use_remote_estimate" is added. If this option is true for a server then server gets the number of rows from remote MySQL server. Server issues an "EXPLAIN" call for the query to remote MySQL server and gets the rows column and filtered column. Using the rows and filtered column, it calculates the actual number of rows for the query.
9) Adding mysql regression's init script.
10) Script create database and all the required table in MySQL's database. Script need to be run before running the regression.
11) Enable / Disable secure authentication by using MYSQL option flag MYSQL_SECURE_AUTH. By default secure authentication is true. This option is added for legacy systems which does not support secure authentication. (#39)
The following bug fixes are done as part of this mysql_fdw release:
1) Fix IMPORT FOREIGN SCHEMA issues with LIMIT/EXCLUDE (pull request #84)
2) Wrapped table names for LIMIT/EXCLUDE in single quotes so these keywords can be used as table names.
3) Modified foreign schema query to use null-safe equals operator
4) Don't send "E" for regular expression. This is needed so regular expressions can work properly. (#77)
5) Builtin functions have different names in PostgreSQL and MySQL. Current implementation is for translating PostgreSQL's btrim to MySQL' trim. To do the translation mysql_deparse_func_expr function performs the replacement. (#70)
6) Don't quote functions in WHERE clause while push down to remote server. The mysql server doesn't execute them as a function if they functions names are quoted. (#42)
7) Don't push WHERE clause in case of PARAM value. Since the param values are not available at the remote server, this ends up causing an error. (#44)
8) Added a check, that forces that the first column of MySQL table must have a unique constraint. (#45)
9) Improvements to pattern matching algorithm
Copyright (c) 2011 - 2016, EnterpriseDB Corporation
Permission to use, copy, modify, and distribute this software and its documentation for any purpose, without fee, and without a written agreement is hereby granted, provided that the above copyright notice and this paragraph and the following two paragraphs appear in all copies.
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