MySQL/OTP – MySQL driver for Erlang/OTP
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README.md

MySQL/OTP

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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 SQL savepoints.
    • Transactions are automatically retried when deadlocks are detected.
  • 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.
  • SSL.
  • Parametrized queries using cached prepared statements (What?)
  • Slow queries are interrupted without killing the connection (MySQL version ≥ 5.0.0)
  • Implements both protocols: the binary protocol for prepared statements and the text protocol for plain queries.

See also:

Synopsis

%% Connect (ssl is optional)
{ok, Pid} = mysql:start_link([{host, "localhost"}, {user, "foo"},
                              {password, "hello"}, {database, "test"},
                              {ssl, [{cacertfile, "/path/to/ca.pem"}]}]),

%% 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 1.3.2

Using rebar:

{deps, [
    {mysql, ".*", {git, "https://github.com/mysql-otp/mysql-otp",
                   {tag, "1.3.2"}}}
]}.

Tests

EUnit tests are executed using make tests or make eunit.

To run individual test suites, use make eunit t=SUITE where SUITE is one of mysql_encode_tests, mysql_protocol_tests, mysql_tests, ssl_tests or transaction_tests.

The encode and protocol test suites does not require a running MySQL server on localhost.

For the suites mysql_tests, ssl_tests and transaction_tests you need to start MySQL on localhost and give privileges to the user otptest and (for ssl_tests) to the user otptestssl:

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

Before running the test suite ssl_tests you'll also need to generate SSL files and MySQL extra config file. In order to do so, please execute make tests-prep.

The MySQL server configuration must include my-ssl.cnf file, which can be found in test/ssl/. Do not run make tests-prep after you start MySQL, because CA certificates will no longer match.

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.

Contributing

Run the tests and also dialyzer using make dialyze.

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.

Maintaining

This is for the project's maintainer(s) only.

Tagging a new version:

  1. Before tagging, update src/mysql.app.src and README.md with the new version.
  2. Tag and push tags using git push --tags.
  3. After tagging a new version:
  • Update the changelog using make CHANGELOG.md and commit it.
  • Update the online documentation and coverage reports using make gh-pages. Then push the gh-pages branch using git push origin gh-pages.

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!