Postgresql Code Review

-- ❌ BAD: Inefficient JSONB usage
SELECT * FROM orders WHERE data->>'status' = 'shipped';  -- No index support

-- ✅ GOOD: Indexable JSONB queries
CREATE INDEX idx_orders_status ON orders USING gin((data->'status'));
SELECT * FROM orders WHERE data @> '{"status": "shipped"}';

-- ❌ BAD: Deep nesting without consideration
UPDATE orders SET data = data || '{"shipping":{"tracking":{"number":"123"}}}';

-- ✅ GOOD: Structured JSONB with validation
ALTER TABLE orders ADD CONSTRAINT valid_status 
CHECK (data->>'status' IN ('pending', 'shipped', 'delivered'));

-- ❌ BAD: Inefficient array operations
SELECT * FROM products WHERE 'electronics' = ANY(categories);  -- No index

-- ✅ GOOD: GIN indexed array queries
CREATE INDEX idx_products_categories ON products USING gin(categories);
SELECT * FROM products WHERE categories @> ARRAY['electronics'];

-- ❌ BAD: Array concatenation in loops
-- This would be inefficient in a function/procedure

-- ✅ GOOD: Bulk array operations
UPDATE products SET categories = categories || ARRAY['new_category']
WHERE id IN (SELECT id FROM products WHERE condition);

-- ❌ BAD: Not using PostgreSQL features
CREATE TABLE users (
    id INTEGER,
    email VARCHAR(255),
    created_at TIMESTAMP
);

-- ✅ GOOD: PostgreSQL-optimized schema
CREATE TABLE users (
    id BIGSERIAL PRIMARY KEY,
    email CITEXT UNIQUE NOT NULL,  -- Case-insensitive email
    created_at TIMESTAMPTZ DEFAULT NOW(),
    metadata JSONB DEFAULT '{}',
    CONSTRAINT valid_email CHECK (email ~* '^[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,}$')
);

-- Add JSONB GIN index for metadata queries
CREATE INDEX idx_users_metadata ON users USING gin(metadata);

-- ❌ BAD: Using generic types for specific data
CREATE TABLE transactions (
    amount DECIMAL(10,2),
    currency VARCHAR(3),
    status VARCHAR(20)
);

-- ✅ GOOD: PostgreSQL custom types
CREATE TYPE currency_code AS ENUM ('USD', 'EUR', 'GBP', 'JPY');
CREATE TYPE transaction_status AS ENUM ('pending', 'completed', 'failed', 'cancelled');
CREATE DOMAIN positive_amount AS DECIMAL(10,2) CHECK (VALUE > 0);

CREATE TABLE transactions (
    amount positive_amount NOT NULL,
    currency currency_code NOT NULL,
    status transaction_status DEFAULT 'pending'
);

-- ❌ BAD: Inefficient trigger function
CREATE OR REPLACE FUNCTION update_modified_time()
RETURNS TRIGGER AS $$
BEGIN
    NEW.updated_at = NOW();  -- Should use TIMESTAMPTZ
    RETURN NEW;
END;
$$ LANGUAGE plpgsql;

-- ✅ GOOD: Optimized trigger function
CREATE OR REPLACE FUNCTION update_modified_time()
RETURNS TRIGGER AS $$
BEGIN
    NEW.updated_at = CURRENT_TIMESTAMP;
    RETURN NEW;
END;
$$ LANGUAGE plpgsql;

-- Set trigger to fire only when needed
CREATE TRIGGER update_modified_time_trigger
    BEFORE UPDATE ON table_name
    FOR EACH ROW
    WHEN (OLD.* IS DISTINCT FROM NEW.*)
    EXECUTE FUNCTION update_modified_time();

-- ✅ Check if extension exists before creating
CREATE EXTENSION IF NOT EXISTS "uuid-ossp";
CREATE EXTENSION IF NOT EXISTS "pgcrypto";
CREATE EXTENSION IF NOT EXISTS "pg_trgm";

-- ✅ Use extensions appropriately
-- UUID generation
SELECT uuid_generate_v4();

-- Password hashing
SELECT crypt('password', gen_salt('bf'));

-- Fuzzy text matching
SELECT word_similarity('postgres', 'postgre');

-- ✅ GOOD: Implementing RLS
ALTER TABLE sensitive_data ENABLE ROW LEVEL SECURITY;

CREATE POLICY user_data_policy ON sensitive_data
    FOR ALL TO application_role
    USING (user_id = current_setting('app.current_user_id')::INTEGER);

-- ❌ BAD: Overly broad permissions
GRANT ALL PRIVILEGES ON ALL TABLES IN SCHEMA public TO app_user;

-- ✅ GOOD: Granular permissions
GRANT SELECT, INSERT, UPDATE ON specific_table TO app_user;
GRANT USAGE ON SEQUENCE specific_table_id_seq TO app_user;