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Database ​

Ratchet is able to connect to SQLite, MySQL and PostgreSQL databases.

This way you can not only store and read persistent data, but you can also easily integrate your systems with web applications that share the same database.

dbConnect function ​

This function creates a database connection object that other functions can be used with, or fails and returns nil value.

Allowed database type inputs are: sqlite3, sqlite, mysql, postgres, postgresql

Connection string can be a file path for SQLite, or a space separated list of parameters. Refer to examples below to use them properly.

Syntax:

lua
DatabaseConnection|nil dbConnect( string databaseType, string connectionString [, int timeout = 500 ] )

Example:

lua
local db = dbConnect("sqlite3", "data/test.db")
lua
local db = dbConnect("mysql", "db=test user=root password=123")
lua
local db = dbConnect("postgres", "dbname=mydatabase")

Connection parameters ​

Important things are the name of the database; username and password if applicable. Most likely you don't need anything else. And if you don't understand them, then you certainly don't need them. All of these options are optional except for the dbname which is required in all database types.

SQLite ​

  • dbname or db - this parameter is required unless the entire connection string is just the database name, in which case it must not contain any = signs
  • timeout - set busy timeout in seconds (link)
  • readonly - open database in read-only mode instead of the default read-write (note that the database file must already exist in this case)
  • nocreate - open an existing database without creating a new one if it doesn't already exist (by default, a new database file is created)
  • synchronous - set the pragma synchronous flag (link)
  • shared_cache - enable or disabled shared pager cache (link)
  • vfs - set the SQLite VFS used to as OS interface (link)
  • foreign_keys - set the pragma foreign_keys flag (link)

Boolean options readonly, nocreate, and shared_cache can be either specified without any value, which is equivalent to setting them to 1, or set to one of 1, yes, true or on to enable the option or 0, no, false or off to disable it. Specifying any other value results in an error.

MySQL ​

  • dbname, db or service (required)
  • user
  • password or pass
  • host
  • port
  • unix_socket
  • sslca
  • sslcert
  • local_infile - should be 0 or 1, 1 means MYSQL_OPT_LOCAL_INFILE will be set
  • charset
  • reconnect - if set to 1, set MYSQL_OPT_RECONNECT to reconnect on connection loss
  • connect_timeout - should be positive integer value that means seconds corresponding to MYSQL_OPT_CONNECT_TIMEOUT
  • read_timeout - should be positive integer value that means seconds corresponding to MYSQL_OPT_READ_TIMEOUT
  • write_timeout - should be positive integer value that means seconds corresponding to MYSQL_OPT_WRITE_TIMEOUT
  • ssl_mode - should be one of the name constants DISABLED, PREFERRED, REQUIRED, VERIFY_CA or VERIFY_IDENTITY corresponding to MYSQL_OPT_SSL_MODE options (note that this option is currently not supported when using MariaDB)

Postgres ​

Too many options to list, refer to:

https://www.postgresql.org/docs/current/libpq-connect.html#LIBPQ-PARAMKEYWORDS

Usage ​

query function ​

Standard SQL query. Only use this if you're not passing any user supplied arguments into the query string, otherwise use prepared statements for better security.

Syntax:

lua
void DatabaseConnection:query( string query [, function ( bool success, string error, table|nil rows ) ] )

Example:

lua
local db = dbConnect("sqlite3", "data/test.db")
db:query("SELECT `value` FROM `settings` WHERE `key` = 'motd'",
function(success, error, rows)
    print(rows[1].value)
end)

exec function ​

SQL query is executed and no result is expected, instead a number of affected rows is returned. This is mainly useful for INSERT, DELETE and UPDATE queries.

Syntax:

lua
void DatabaseConnection:exec( string query [, function ( bool success, string error, int|nil affected ) ] )

Example:

lua
local db = dbConnect("sqlite3", "data/test.db")
db:exec("UPDATE `settings` SET `value` = 'Hello world!' WHERE `key` = 'motd'",
function(success, error, affected)
    print(affected)
end)

prepare function ​

Prepared statements are very useful to prevent SQL injection. Every ? in the query string will be replaced by corresponding value in the data table in order.

Syntax:

lua
void DatabaseConnection:prepare( string query, table data [, function ( bool success, string error, table|int|nil rows ) ] )

Example:

lua
local db = dbConnect("sqlite3", "data/test.db")
db:prepare("SELECT `value` FROM `settings` WHERE `key` = ?", { "motd" },
function(success, error, rows)
    print(rows[1].value)
end)

db:prepare("UPDATE `settings` SET `value` = ? WHERE `key` = ?", { "Hello world!", "motd" },
function(success, error, affected)
    print(affected)
end)

close function ​

Safely close a database connection when it's no longer needed.

Syntax:

lua
void DatabaseConnection:close()

Example:

lua
local db = dbConnect("sqlite3", "data/test.db")
db:close()

isConnected function ​

Check whether database connection is still active.

Syntax:

lua
bool DatabaseConnection:isConnected()

Example:

lua
local db = dbConnect("sqlite3", "data/test.db")
print(db:isConnected())