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Database

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


💂Authority
This class can only be spawned on 🟦 Server side.

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?)
TypeNameDefaultDescription
DatabaseEnginedatabase_engineDatabase Engine
stringconnection_stringConnection String used to create and connect to the database
integerpool_size10Size 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

ReturnsNameDescription
CloseCloses the Database
ExecuteAsyncExecute a query asynchronously
integer, stringExecuteExecute a query synchronously
SelectAsyncExecute a select query asynchronously
table of table, stringSelectSelects a query synchronously

Close

Closes the Database

my_database:Close()

ExecuteAsync

Execute a query asynchronously

my_database:ExecuteAsync(query, callback?, parameters...?)
TypeParameterDefaultDescription
stringqueryQuery to execute
functioncallback?nilCallback in the format (rows_affected, error)
anyparameters...?nilSequence of parameters to escape into the Query

Execute

Execute a query synchronously

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

local ret_01, ret_02 = my_database:Execute(query, parameters...?)
TypeParameterDefaultDescription
stringqueryQuery to execute
anyparameters...?nilSequence of parameters to escape into the Query

SelectAsync

Execute a select query asynchronously

my_database:SelectAsync(query, callback?, parameters...?)
TypeParameterDefaultDescription
stringqueryQuery to execute
functioncallback?nilCallback in the format (rows: table[], error: string?)
anyparameters...?nilSequence of parameters to escape into the Query

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...?)
TypeParameterDefaultDescription
stringqueryQuery to execute
anyparameters...?nilSequence 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.

ParameterDefault ValueDescription
db/dbnameThe database name
timeout0set sqlite busy timeout (in seconds) (link)
readonlyfalseopen 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)
synchronousset the pragma synchronous flag (link)
shared_cacheshould be true (link)
vfsset the SQLite VFS used to as OS interface. The VFS should be registered before opening the connection, see the documentation

▶ MySQL

ParameterDefault ValueDescription
db/dbnameThe database name
userUser name to connect as
password/passPassword to be used if the server demands password authentication
hostName of host to connect to
portPort number to connect to at the server host
unix_socket
sslca
sslcert
local_infileshould be 0 or 1, 1 means MYSQL_OPT_LOCAL_INFILE will be set
charset
reconnect0if set to 1, will attempt to reconnect on connection loss
connect_timeoutshould be positive integer value that means seconds corresponding to MYSQL_OPT_CONNECT_TIMEOUT
read_timeoutshould be positive integer value that means seconds corresponding to MYSQL_OPT_READ_TIMEOUT
write_timeoutshould 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.

ParameterDefault ValueDescription
hostName of host to connect to
hostaddrNumeric IP address of host to connect to
portPort number to connect to at the server host
usersame as OS user nameUser name to connect as
dbnamesame as user nameThe database name
passwordPassword to be used if the server demands password authentication
connect_timeout0Maximum wait for connection, in seconds
optionsCommand-line options to be sent to the server