-- Add unique constraint for comment reactions if it doesn't exist
DO $$
BEGIN
    IF NOT EXISTS (
        SELECT 1 FROM information_schema.table_constraints 
        WHERE constraint_name = 'unique_comment_user_reaction' 
        AND table_name = 'comment_reactions'
    ) THEN
        ALTER TABLE comment_reactions ADD CONSTRAINT unique_comment_user_reaction UNIQUE (comment_id, user_id);
    END IF;
END $$;