MySQL.jl

Julia bindings and helper functions for MariaDB/MySQL C library. Query results can be received as julia arrays or as Data Frames.

Installation

To get the master version:

Pkg.clone("https://github.com/JuliaComputing/MySQL.jl")

Example usage

Connect to the MySQL server:

using MySQL
con = mysql_connect(HOST, USER, PASSWD, DBNAME)

Create/Insert/Update etc:

command = """CREATE TABLE Employee
             (
                 ID INT NOT NULL AUTO_INCREMENT,
                 Name VARCHAR(255),
                 Salary FLOAT,
                 JoinDate DATE,
                 LastLogin DATETIME,
                 LunchTime TIME,
                 PRIMARY KEY (ID)
             );"""
response = mysql_query(con, command)
if (response == 0)
    println("Create table succeeded.")
else
    println("Create table failed.")
end

Obtain SELECT results as dataframe:

command = """SELECT * FROM Employee;"""
dframe = execute_query(con, command)

The mysql_execute_query() API will take care of handling errors and freeing the memory allocated to the results.

Obtain SELECT results as julia Array:

command = """SELECT * FROM Employee;"""
retarr = mysql_execute_query(con, command, opformat=MYSQL_ARRAY)

Iterate over rows:

response = mysql_query(con, "SELECT * FROM some_table;")
mysql_display_error(con, response != 0,
                    "Error occured while executing mysql_query on \"$command\"")

result = mysql_store_result(con)

for row in MySQLRowIterator(result)
    println(row)
end

mysql_free_result(result)

Get metadata of fields:

response = mysql_query(con, "SELECT * FROM some_table;")
mysql_display_error(con, response != 0,
                    "Error occured while executing mysql_query on \"$command\"")

result = mysql_store_result(con)
mysqlfields = mysql_get_field_metadata(result)
for i = 1:length(mysqlfields)
    field = mysqlfields[i]
    println("Field name is: ", bytestring(field.name))
    println("Field length is: ", field_length)
    println("Field type is: ", field_type)
end

Execute a multi query:

command = """INSERT INTO Employee (Name) VALUES ('');
             UPDATE Employee SET LunchTime = '15:00:00' WHERE LENGTH(Name) > 5;"""
data = mysql_execute_multi_query(con, command)

data contains an array of dataframes (or arrays if MYSQL_ARRAY was specified as the 3rd argument to the above API) corresponding to the SELECT queries and number of affected rows corresponding to the non-SELECT queries in the multi statement.

Get dataframes using prepared statements:

command = """SELECT * FROM Employee;"""

stmt = mysql_stmt_init(con)

if (stmt == C_NULL)
    error("Error in initialization of statement.")
end

response = mysql_stmt_prepare(stmt, command)
mysql_display_error(con, response != 0,
                    "Error occured while preparing statement for query \"$command\"")

dframe = mysql_stmt_result_to_dataframe(stmt)
mysql_stmt_close(stmt)

Close the connection:

mysql_disconnect(con)

How to solve MySQL library not found error

This error may occur during using MySQL. To resolve this-

• Ubuntu: Just add the MariaDB/MySQL .so file to lib_choices array in src/config.jl. If it is already there make sure LD_LIBRARY_PATH contains the MariaDB/MySQL .so file directory path. Usually this is something like /usr/local/lib/mariadb/.
• OSX: Same as above. In this case the file will be something like libmysqlclient.dylib.
• Windows: There is no @windows_only lib_choices currently. Please add one and send a pull request.

Tests

To run the tests you must have MySQL server running on the host. Set the constants HOST and ROOTPASS in test/runtests.jl to the host and root password on your test setup. Run the tests using:

Pkg.test("MySQL")

Performance

A total of 67,000 insert queries were executed batch wise in batch sizes of 50, 100, 150 ... so on. The time taken for all the queries to complete is plotted on the y axis and the batch sizes on x axis.

Acknowledgement

We acknowledge the contributions of JustDial towards this work.