Greenplum PL/pgSQL: Stored Procedures and Functions

In Greenplum, PL/pgSQL is a procedural language extension that allows you to write stored procedures and functions using the PostgreSQL PL/pgSQL syntax. PL/pgSQL is a powerful and flexible language for developing server-side functions within the Greenplum Database. Here's an overview of creating stored procedures and functions using PL/pgSQL:

 1. Creating PL/pgSQL Functions:

 1.1 Syntax:

CREATE OR REPLACE FUNCTION function_name (parameter1 datatype, parameter2 datatype, ...)

RETURNS return_datatype AS 

DECLARE

    -- Variable declarations

BEGIN

    -- Function body (PL/pgSQL code)

END;

 LANGUAGE plpgsql;

 1.2 Example:

CREATE OR REPLACE FUNCTION add_numbers(a INT, b INT)

RETURNS INT AS 

DECLARE

    result INT;

BEGIN

    result := a + b;

    RETURN result;

END;

 LANGUAGE plpgsql;

 2. Calling PL/pgSQL Functions:

 2.1 Syntax:

SELECT function_name(parameter1, parameter2, ...);

 2.2 Example:

SELECT add_numbers(5, 7);

 3. PL/pgSQL Stored Procedures:

 3.1 Syntax:

CREATE OR REPLACE PROCEDURE procedure_name (parameter1 datatype, parameter2 datatype, ...)

AS 

DECLARE

    -- Variable declarations

BEGIN

    -- Procedure body (PL/pgSQL code)

END;

 LANGUAGE plpgsql;

 3.2 Example:

CREATE OR REPLACE PROCEDURE print_message(message TEXT)

AS 

DECLARE

    current_time TIMESTAMP;

BEGIN

    current_time := NOW();

    RAISE NOTICE 'Message: %, Current Time: %', message, current_time;

END;

 LANGUAGE plpgsql;

 4. Calling PL/pgSQL Procedures:

 4.1 Syntax:

CALL procedure_name(parameter1, parameter2, ...);

 4.2 Example:

CALL print_message('Hello, Greenplum!');

 5. PL/pgSQL Variables and Control Structures:

- Variables: Declare variables using the DECLARE keyword.

- Control Structures: Use IF, CASE, LOOP, WHILE, and other control structures to implement conditional and iterative logic.

 6. Exception Handling:

- Use EXCEPTION blocks to handle errors and exceptions within PL/pgSQL code.

 7. Returning Result Sets:

- Functions can return result sets using RETURN QUERY along with a SELECT statement.

 8. Security Considerations:

- Grant appropriate permissions to users for executing functions or procedures.

 9. Dropping Functions or Procedures:

- Use DROP FUNCTION or DROP PROCEDURE to remove stored functions or procedures.

 Example of a PL/pgSQL Function with Result Set:

CREATE OR REPLACE FUNCTION get_employee_names()

RETURNS TABLE (first_name VARCHAR, last_name VARCHAR) AS 

BEGIN

    RETURN QUERY SELECT first_name, last_name FROM employees;

END;

 LANGUAGE plpgsql;

 Example of a PL/pgSQL Procedure:

CREATE OR REPLACE PROCEDURE update_employee_salary(employee_id INT, new_salary DECIMAL)

AS 

BEGIN

    UPDATE employees SET salary = new_salary WHERE id = employee_id;

    COMMIT;

END;

 LANGUAGE plpgsql;

PL/pgSQL provides a wide range of capabilities for developing complex stored procedures and functions within Greenplum. The syntax is similar to that of PostgreSQL, as Greenplum is based on the PostgreSQL database system. Keep in mind that, as of my last knowledge update in January 2022, Greenplum's features and capabilities may have evolved, so it's recommended to refer to the latest Greenplum documentation for the most up-to-date information.