Database

The Database entity provides programmers a way to access SQL databases easily through scripting.

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💂Authority

This class can only be spawned on 🟦 Server side.

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tip

Currently HELIX supports SQLite, MySQL and PostgreSQL out of the box.

Examples

Server/Index.lua

-- Creates a SQLite connection, using a local file called 'database_filename.db'
local sqlite_db = Database(DatabaseEngine.SQLite, "db=database_filename.db timeout=2")

-- Creates a table
sqlite_db:Execute([[
    CREATE TABLE IF NOT EXISTS test (
        id INTEGER,
        name VARCHAR(100)
    )
]])

-- Insert values in the table
local affected_rows = sqlite_db:Execute("INSERT INTO test VALUES (1, 'amazing')")
Console.Log("Affected Rows: " .. tostring(affected_rows))
-- Will output: 1

-- Selects the data
local rows = sqlite_db:Select("SELECT * FROM test")
Console.Log(HELIXTable.Dump(rows))
-- Will output a table with all data from 'test'

-- Selects the data with filter
local rows_filter = sqlite_db:Select("SELECT * FROM test WHERE name = :0", "amazing")
Console.Log(HELIXTable.Dump(rows_filter))
-- Will output a table with all data from 'test' where name matches 'amazing'

tip

All requests are thread safe! 🥳

Constructors

Default Constructor

local my_database = Database(database_engine, connection_string, pool_size?)

Type	Name	Default	Description
DatabaseEngine	database_engine		Database Engine
string	connection_string		Connection String used to create and connect to the database
integer	pool_size	10	Size of the connection pool when calling several queries simultaneously

note

The initial connection to the Database (when it's being constructed) is made on the main thread, so expect the server hanging for a few seconds during that.

info

If the Database fails to connect, it will spit an error on console and will return nil.

Static Functions

This entity doesn't have own static functions.

Functions

	Returns	Name	Description
		Close	Closes the Database
		ExecuteAsync	Execute a query asynchronously
	integer, string	Execute	Execute a query synchronously
		SelectAsync	Execute a select query asynchronously
	table of table, string	Select	Selects a query synchronously

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Close

Closes the Database

my_database:Close()

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ExecuteAsync

Execute a query asynchronously

my_database:ExecuteAsync(query, callback?, parameters...?)

Type	Parameter	Default	Description
string	query		Query to execute
function	callback?	nil	Callback in the format (rows_affected, error)
any	parameters...?	nil	Sequence of parameters to escape into the Query

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Execute

Execute a query synchronously

— Returns integer, string (affected rows, error (if any)).

local ret_01, ret_02 = my_database:Execute(query, parameters...?)

Type	Parameter	Default	Description
string	query		Query to execute
any	parameters...?	nil	Sequence of parameters to escape into the Query

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SelectAsync

Execute a select query asynchronously

my_database:SelectAsync(query, callback?, parameters...?)

Type	Parameter	Default	Description
string	query		Query to execute
function	callback?	nil	Callback in the format (rows: table[], error: string?)
any	parameters...?	nil	Sequence of parameters to escape into the Query

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Select

Selects a query synchronously

— Returns table of table, string (rows fetched, error (if any)).

local ret_01, ret_02 = my_database:Select(query, parameters...?)

Type	Parameter	Default	Description
string	query		Query to execute
any	parameters...?	nil	Sequence of parameters to escape into the Query

tip

When passing arguments to a query, use the following syntax: :? where ? is the placeholder argument (i.e. :0) passed into the function.

For a more in-depth example see Examples

🧵 Connection String

Each Database Engine has it's own parameters which can be used on the connection_string constructor. Those parameters are defined and backend-dependent by the Engine, being passed directly to the Backend when creating the connection.

They should be set in the following format: "param1=value1 param2=value2 param3=value3".

tip

Usually you don't need to explicitly define all (or most) of the parameters described here, just use the ones you make sure are useful for your needs. Some of them are described by the libraries but aren't 100% tested in HELIX.

▶ SQLite

tip

There is a special connection_string for SQLite: :memory:. This will create a database in the memory which is destroyed when the server closes.

Parameter	Default Value	Description
db/dbname		The database name
timeout	0	set sqlite busy timeout (in seconds) (link)
readonly	false	open database in read-only mode instead of the default read-write (note that the database file must already exist in this case, see the documentation)
synchronous		set the pragma synchronous flag (link)
shared_cache		should be true (link)
vfs		set the SQLite VFS used to as OS interface. The VFS should be registered before opening the connection, see the documentation

▶ MySQL

Parameter	Default Value	Description
db/dbname		The database name
user		User name to connect as
password/pass		Password to be used if the server demands password authentication
host		Name of host to connect to
port		Port number to connect to at the server host
unix_socket
sslca
sslcert
local_infile		should be 0 or 1, 1 means MYSQL_OPT_LOCAL_INFILE will be set
charset
reconnect	0	if set to 1, will attempt 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

▶ PostgreSQL

More parameters and complete information can be found at the PostgreSQL Official Documentation.

Parameter	Default Value	Description
host		Name of host to connect to
hostaddr		Numeric IP address of host to connect to
port		Port number to connect to at the server host
user	same as OS user name	User name to connect as
dbname	same as user name	The database name
password		Password to be used if the server demands password authentication
connect_timeout	0	Maximum wait for connection, in seconds
options		Command-line options to be sent to the server