access-europe / mysql-otp

MySQL/OTP – MySQL driver for Erlang/OTP

MySQL/OTP

MySQL/OTP is a driver for connecting Erlang/OTP applications to MySQL databases (version 4.1 and upward). It is a native implementation of the MySQL protocol in Erlang.

Some of the features:

• Mnesia style transactions:
  • Nested transactions are implemented using savepoints.
  • Transactions are automatically retried when deadlocks are detected.
• Uses the binary protocol for prepared statements.
• Each connection is a gen_server, which makes it compatible with Poolboy (for connection pooling) and ordinary OTP supervisors.
• No records in the public API.
• Slow queries are interrupted without killing the connection (MySQL version ≥ 5.0.0).

See also:

• API documenation (Edoc)
• Test coverage (EUnit)
• Why another MySQL driver? in the wiki
• MySQL/OTP + Poolboy: A simple application that combines MySQL/OTP with Poolboy for connection pooling.

Synopsis

%% Connect
{ok, Pid} = mysql:start_link([{host, "localhost"}, {user, "foo"},
                              {password, "hello"}, {database, "test"}]),

%% Select
{ok, ColumnNames, Rows} =
    mysql:query(Pid, <<"SELECT * FROM mytable WHERE id = ?">>, [1]),

%% Manipulate data
ok = mysql:query(Pid, "INSERT INTO mytable (id, bar) VALUES (?, ?)", [1, 42]),

%% Separate calls to fetch more info about the last query
LastInsertId = mysql:insert_id(Pid),
AffectedRows = mysql:affected_rows(Pid),
WarningCount = mysql:warning_count(Pid),

%% Mnesia style transaction (nestable)
Result = mysql:transaction(Pid, fun () ->
    ok = mysql:query(Pid, "INSERT INTO mytable (foo) VALUES (1)"),
    throw(foo),
    ok = mysql:query(Pid, "INSERT INTO mytable (foo) VALUES (1)")
end),
case Result of
    {atomic, ResultOfFun} ->
        io:format("Inserted 2 rows.~n");
    {aborted, Reason} ->
        io:format("Inserted 0 rows.~n")
end

%% Multiple queries and multiple result sets
{ok, [{[<<"foo">>], [[42]]}, {[<<"bar">>], [[<<"baz">>]]}]} =
    mysql:query(Pid, "SELECT 42 AS foo; SELECT 'baz' AS bar;"),

%% Graceful timeout handling: SLEEP() returns 1 when interrupted
{ok, [<<"SLEEP(5)">>], [[1]]} =
    mysql:query(Pid, <<"SELECT SLEEP(5)">>, 1000),

Usage as a dependency

Using erlang.mk:

DEPS = mysql
dep_mysql = git https://github.com/mysql-otp/mysql-otp 1.2.0

Using rebar:

{deps, [
    {mysql, ".*", {git, "https://github.com/mysql-otp/mysql-otp",
                   {tag, "1.2.0"}}}
]}.

Contributing

Run the eunit tests with make tests. For the suite mysql_tests you need MySQL running on localhost and give privileges to the otptest user:

grant all privileges on otptest.* to otptest@localhost identified by 'otptest';

If you run make tests COVER=1 a coverage report will be generated. Open cover/index.html to see that any lines you have added or modified are covered by a test.

Linebreak code to 80 characters per line and follow a coding style similar to that of existing code.

Keep commit messages short and descriptive. Each commit message should describe the purpose of the commit, the feature added or bug fixed, so that the commit log can be used as a comprehensive change log. CHANGELOG.md is generated from the commit messages.

License

GNU Lesser General Public License (LGPL) version 3 or any later version. Since the LGPL is a set of additional permissions on top of the GPL, both license texts are included in the files COPYING and COPYING.LESSER respectively.

We hope this license should be permissive enough while remaining copyleft. If you're having issues with this license, please create an issue in the issue tracker!