Support Unix Domain Sockets for MySQL

[pimeys]

We need this in many cases, especially when working with Google's databases and developer tools, sockets can be quite common.

The Socket implementation in SQLx should not be PostgreSQL-specific as it is right now. Also the socket should be specified by the user, it can be different depending on the environment. For example GCP creates a socket bridge to the disk, which is not the default location found from your normal PostgreSQL installation.

The connection string in MySQL when using a socket should be:

mysql://root@localhost/dbname?socket=(/tmp/mysql.sock)

Then again PostgreSQL has following format for UDS:

postgresql://root@/dbname?host=/tmp/.s.PGSQL.5432

So this issue would require changes for a few things:

• Making Socket to be generic for PostgreSQL and MySQL
• Allowing one to define the location of the socket either through options or connection string

[pimeys]

Also, I'd like to implement this :)

[pimeys]

After a discussion on Discord, the right way to define sockets would be:

PostgreSQL:

postgresql://root@/dbname?host=/tmp
// or
postgresql://root@%2ftmp/dbname

The socket name in the directory is defined from the port, typically being .s.PGSQL.5432 with the default port.

MySQL:

mysql:///database_name?socket=/tmp/mysql.sock

Here we define the full path to the socket file.

[mehcode]

Support was merged in with #450. Thanks @pimeys