Creating a completely new extension for PostgreSQL involves several steps.
Here we will create a basic extension with that adds SQL function to calculate factorial of a given integer. This example is written using the PL/pgSQL procedural language.
Create the Factorial Extension
Setp 1:
Create factorial_extension folder in share
directory in the postgres installation folder.
Set up the folder structure. This folder contains file factorial_extension.control
and factorial_extension--1.0.sql
factorial_extension/
|
+-- factorial_extension.control
|
+-- factorial_extension--1.0.sql
Setp 2:
Write the control file. The control file for an extension, also known as the .control file, is a metadata file that provides information about the extension. It contains details such as the name, version, author, module path, dependencies, and other important attributes of the extension.
# factorial_extension.control
comment = 'Extension to calculate factorial'
default_version = '1.0'
module_pathname = '$libdir/factorial_extension'
relocatable = false
Step 3:
Write the SQL script (factorial_extension--1.0.sql):
-- factorial_extension--1.0.sql
-- Create a new schema for the extension
CREATE SCHEMA factorial_extension;
-- Create the factorial function
CREATE OR REPLACE FUNCTION factorial_extension.factorial(n INTEGER)
RETURNS BIGINT AS $$
DECLARE
result BIGINT := 1;
BEGIN
IF n < 0 THEN
RAISE EXCEPTION 'Factorial is not defined for negative numbers';
ELSIF n > 1 THEN
FOR i IN 2..n LOOP
result := result * i;
END LOOP;
END IF;
RETURN result;
END;
$$ LANGUAGE plpgsql;
-- Grant execute permission to public (change to appropriate roles if needed)
GRANT EXECUTE ON FUNCTION factorial_extension.factorial(INTEGER) TO PUBLIC;
Run the Extension
Step 1: Start or restart the PostgreSQL server
Step 2: Connect to the database where you want to install the extension
Step 3: TO install the extension run the following command.
CREATE EXTENSION factorial_extension;
Use the Extension
SELECT factorial_extension.factorial(5);
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