session_variable

pig build pkg session_variable;		# build rpm/deb

pig repo add pgsql -u   # add both repo and update cache

pig install session_variable;		# install via package name, for the active PG version

pig install session_variable -v 18;   # install for PG 18
pig install session_variable -v 17;   # install for PG 17
pig install session_variable -v 16;   # install for PG 16
pig install session_variable -v 15;   # install for PG 15
pig install session_variable -v 14;   # install for PG 14

CREATE EXTENSION session_variable;

CREATE EXTENSION session_variable;

-- Create a variable with initial value
SELECT session_variable.create_variable('my_var', 'text'::regtype, 'initial text'::text);

-- Create a variable with NULL initial value
SELECT session_variable.create_variable('my_date_var', 'date'::regtype);

-- Create a constant (cannot be changed via set())
SELECT session_variable.create_constant('my_env', 'text'::regtype, 'Production'::text);

-- Get variable value (second arg is type hint)
SELECT session_variable.get('my_var', null::text);

-- Set variable value (returns previous value)
SELECT session_variable.set('my_var', 'new text'::text);

DO $$
DECLARE
    my_field text;
BEGIN
    my_field := session_variable.get('my_var', my_field);
    RAISE NOTICE 'Value: %', my_field;
END
$$ LANGUAGE plpgsql;

-- Alter the initial/constant value (affects new sessions)
SELECT session_variable.alter_value('my_env', 'Development'::text);

-- Reload all variables from database definitions
SELECT session_variable.init();

-- Drop a variable or constant
SELECT session_variable.drop('my_var');

-- Check if a variable exists
SELECT session_variable.exists('my_var');

-- Get the type of a variable
SELECT session_variable.type_of('my_var');