mysql/mysql_client.md

local mysql = require'mysql_client'

MySQL client protocol in Lua. Stolen from OpenResty, modified to work with [sock] and added prepared statements.

Example

local mysql = require'mysql_client'

assert(mysql.connect{
	host = '127.0.0.1',
	port = 3306,
	user = 'bar',
	password = 'baz',
	schema = 'foo',
	charset = 'utf8mb4',
	max_packet_size = 1024 * 1024,
})

assert(cn:query('drop table if exists cats'))

local res = assert(cn:query('create table cats '
			  .. '(id serial primary key, '
			  .. 'name varchar(5))'))

local res = assert(cn:query('insert into cats (name) '
	.. "values ('Bob'),(''),(null)"))

print(res.affected_rows, ' rows inserted into table cats ',
		'(last insert id: ', res.insert_id, ')')

require'pp'(assert(cn:query('select * from cats order by id asc', 10)))

assert(cn:close())

API

mysql.connect(options) -> ok | nil,err,errcode,sqlstate

Connect to a MySQL server.

The options argument is a Lua table holding the following keys:

• host: server's IP address (required).
• port: server's port (optional, defaults to 3306).
• user: user name.
• password: password (optional).
• schema: the schema to set as current schema (optional).
• collation: the collation used for the connection (charset is implied by this).
• use 'server' to get the server's collation and charset for the connection.
• charset: the character set used for the connection.
• if collation not set, the default collation for the charset is selected.
• max_packet_size: the upper limit for the reply packets sent from the server (defaults to 16 MB).
• ssl: if true, then uses SSL to connect to MySQL (defaults to false). If the server does not have SSL support (or just disabled), the error string "ssl disabled on server" is returned.
• ssl_verify: if true, then verifies the validity of the server SSL certificate (default is false).

cn:close() -> 1 | nil,err

Closes the current mysql connection and returns the status.

cn:send_query(query) -> bytes | nil,err

Sends the query to the remote MySQL server without waiting for its replies.

Returns the bytes successfully sent out. Use read_result() to read the replies.

cn:read_result([options]) -> res,nil|'again',cols | nil,err,errcode,sqlstate

Reads in one result returned from the server.

It returns a Lua table (res) describing the MySQL OK packet or result set packet for the query result.

For queries corresponding to a result set, it returns an array holding all the rows.

The options arg can contain:

• compact = true -- return an array of arrays instead of an array of {column->value} maps.
• to_array = true -- return an array of values for single-column results.
• null_value = val -- value to use for null (defaults to nil).

For queries that do not correspond to a result set, it returns a Lua table like this:

    {
        insert_id = 0,
        server_status = 2,
        warning_count = 1,
        affected_rows = 32,
        message = nil
    }

If more results are following the current result, a second err return value will be given the string again. One should always check this (second) return value and if it is again, then she should call this method again to retrieve more results. This usually happens when the original query contains multiple statements (separated by semicolon in the same query string) or calling a MySQL procedure.

In case of errors, this method returns at most 4 values: nil, err, errcode, and sqlstate. The err return value contains a string describing the error, the errcode return value holds the MySQL error code (a numerical value), and finally, the sqlstate return value contains the standard SQL error code that consists of 5 characters. Note that, the errcode and sqlstate might be nil if MySQL does not return them.

cn:query(query, [options]) -> res,nil,cols | nil,err,errcode,sqlstate

This is a shortcut for combining the send_query call and the first read_result call.

You should always check if the err return value is again in case of success because this method will only call read_result once for you.

cn:prepare(query, [opt]) -> stmt

Prepare a statement. Options can contain:

• cursor: 'read_only', 'update', 'scrollabe', 'none' (default: 'none').

stmt:exec(params...)

Execute a statement. Use cn:read_result() to get the results.

stmt:free()

Free statement.

cn.server_ver

The MySQL server version string.

cn:quote(s) -> s

Quote literal string to be used in queries. Quoting only works if current collation is known (ses collation arg on connect()).

Multiple result set support

For a SQL query that produces multiple result-sets, it is always your duty to check the 'again' error message returned by the query, and keep pulling more result sets by calling the read_result() until no 'again' error message returned (or some other errors happen).

Limitations

Authentication

By default, of all authentication methods, only Old Password Authentication(mysql_old_password) and Secure Password Authentication(mysql_native_password) are suppored.

TODO

• implement the data compression support in the protocol.