session_variable

pig build pkg session_variable         # 构建 RPM / DEB 包

pig repo add pgsql -u          # 添加仓库并更新缓存

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 true on success)
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');