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database/migrations/add_reviews_system.sql

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+-- Migration: Add Reviews System
+-- Created: 2026-01-03
+
+-- Create reviews table
+CREATE TABLE IF NOT EXISTS reviews (
+    review_id SERIAL PRIMARY KEY,
+    product_id INTEGER NOT NULL REFERENCES products(product_id) ON DELETE CASCADE,
+    user_id INTEGER NOT NULL REFERENCES users(user_id) ON DELETE CASCADE,
+    rating INTEGER NOT NULL CHECK (rating >= 1 AND rating <= 5),
+    comment TEXT,
+    is_approved BOOLEAN DEFAULT TRUE,
+    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+    updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+    UNIQUE(product_id, user_id) -- One review per user per product
+);
+
+-- Add indexes for better query performance
+CREATE INDEX IF NOT EXISTS idx_reviews_product_id ON reviews(product_id);
+CREATE INDEX IF NOT EXISTS idx_reviews_user_id ON reviews(user_id);
+CREATE INDEX IF NOT EXISTS idx_reviews_rating ON reviews(rating);
+CREATE INDEX IF NOT EXISTS idx_reviews_created_at ON reviews(created_at);
+
+-- Add rating and review_count columns to products table if they don't exist
+DO $$ 
+BEGIN
+    IF NOT EXISTS (SELECT 1 FROM information_schema.columns 
+                   WHERE table_name='products' AND column_name='rating') THEN
+        ALTER TABLE products ADD COLUMN rating DECIMAL(3,2) DEFAULT 0.00;
+    END IF;
+    
+    IF NOT EXISTS (SELECT 1 FROM information_schema.columns 
+                   WHERE table_name='products' AND column_name='review_count') THEN
+        ALTER TABLE products ADD COLUMN review_count INTEGER DEFAULT 0;
+    END IF;
+END $$;
+
+-- Create function to automatically update updated_at timestamp
+CREATE OR REPLACE FUNCTION update_reviews_updated_at()
+RETURNS TRIGGER AS $$
+BEGIN
+    NEW.updated_at = CURRENT_TIMESTAMP;
+    RETURN NEW;
+END;
+$$ LANGUAGE plpgsql;
+
+-- Create trigger for reviews updated_at
+DROP TRIGGER IF EXISTS trigger_reviews_updated_at ON reviews;
+CREATE TRIGGER trigger_reviews_updated_at
+    BEFORE UPDATE ON reviews
+    FOR EACH ROW
+    EXECUTE FUNCTION update_reviews_updated_at();
+
+-- Function to update product rating and review count
+CREATE OR REPLACE FUNCTION update_product_rating(p_product_id INTEGER)
+RETURNS VOID AS $$
+DECLARE
+    avg_rating DECIMAL(3,2);
+    total_reviews INTEGER;
+BEGIN
+    SELECT COALESCE(AVG(rating), 0.00), COUNT(*)
+    INTO avg_rating, total_reviews
+    FROM reviews
+    WHERE product_id = p_product_id AND is_approved = TRUE;
+    
+    UPDATE products
+    SET rating = avg_rating,
+        review_count = total_reviews,
+        updated_at = CURRENT_TIMESTAMP
+    WHERE product_id = p_product_id;
+END;
+$$ LANGUAGE plpgsql;
+
+-- Create trigger to auto-update product rating after review changes
+CREATE OR REPLACE FUNCTION trigger_update_product_rating()
+RETURNS TRIGGER AS $$
+BEGIN
+    IF TG_OP = 'DELETE' THEN
+        PERFORM update_product_rating(OLD.product_id);
+        RETURN OLD;
+    ELSE
+        PERFORM update_product_rating(NEW.product_id);
+        RETURN NEW;
+    END IF;
+END;
+$$ LANGUAGE plpgsql;
+
+DROP TRIGGER IF EXISTS trigger_review_insert_update_product_rating ON reviews;
+CREATE TRIGGER trigger_review_insert_update_product_rating
+    AFTER INSERT OR UPDATE ON reviews
+    FOR EACH ROW
+    EXECUTE FUNCTION trigger_update_product_rating();
+
+DROP TRIGGER IF EXISTS trigger_review_delete_update_product_rating ON reviews;
+CREATE TRIGGER trigger_review_delete_update_product_rating
+    AFTER DELETE ON reviews
+    FOR EACH ROW
+    EXECUTE FUNCTION trigger_update_product_rating();
+
+-- Grant permissions (adjust as needed)
+-- GRANT ALL PRIVILEGES ON TABLE reviews TO your_db_user;
+-- GRANT USAGE, SELECT ON SEQUENCE reviews_review_id_seq TO your_db_user;
+