PostgreSQL PL/pgSQL Skill Skill

PostgreSQL PL/pgSQL Skill

Atomic skill for procedural programming

Overview

Production-ready patterns for functions, procedures, triggers, and exception handling.

Prerequisites

PostgreSQL 16+
Understanding of SQL

Parameters

parameters:
  code_type:
    type: string
    required: true
    enum: [function, procedure, trigger, aggregate]
  volatility:
    type: string
    enum: [IMMUTABLE, STABLE, VOLATILE]

Quick Reference

Function Template

CREATE OR REPLACE FUNCTION func_name(p_param TYPE)
RETURNS return_type
LANGUAGE plpgsql STABLE SECURITY DEFINER
SET search_path = app, public
AS $$ DECLARE v_result TYPE; BEGIN
    -- Logic
    RETURN v_result;
EXCEPTION WHEN OTHERS THEN
    RAISE WARNING '%', SQLERRM;
    RETURN NULL;
END; $$;

Trigger Template

CREATE OR REPLACE FUNCTION trigger_func() RETURNS TRIGGER AS $$
BEGIN
    IF TG_OP = 'UPDATE' THEN NEW.updated_at := NOW(); END IF;
    RETURN NEW;
END; $$ LANGUAGE plpgsql;

CREATE TRIGGER trg_name BEFORE UPDATE ON t FOR EACH ROW EXECUTE FUNCTION trigger_func();

Volatility

| Category | Use Case | |----------|----------| | IMMUTABLE | Math, formatting | | STABLE | Lookups (no writes) | | VOLATILE | INSERT, random() |

Exception Handling

EXCEPTION
    WHEN unique_violation THEN ...  -- 23505
    WHEN foreign_key_violation THEN ...  -- 23503
    WHEN OTHERS THEN RAISE EXCEPTION '% [%]', SQLERRM, SQLSTATE;

Troubleshooting

| Error | Cause | Solution | |-------|-------|----------| | 42883 | Function not found | Check signature | | 42P13 | Invalid definition | Review syntax | | Trigger not firing | Wrong timing | Check BEFORE/AFTER |

Usage

Skill("postgresql-plpgsql")

Agent Skills: PostgreSQL PL/pgSQL Skill

Skill Files