-- ============================================================================
-- MIGRATION: Add message read tracking
-- ============================================================================
-- Run this migration to add the read_at field to messages table
-- This enables tracking of read/unread messages for notifications
-- Date: 2025-12-17
-- ============================================================================

-- Add read_at column to messages table if it doesn't exist
ALTER TABLE messages ADD COLUMN IF NOT EXISTS read_at TIMESTAMP DEFAULT NULL;

-- Create index on read_at for faster unread message queries
CREATE INDEX IF NOT EXISTS idx_messages_read_at ON messages(read_at);

-- Create index for unread message queries (conversation + read status + sender)
CREATE INDEX IF NOT EXISTS idx_messages_unread ON messages(conversation_id, read_at, sender_id);

-- ============================================================================
-- VERIFICATION QUERIES (Run these to verify the changes)
-- ============================================================================
-- Check if read_at column exists:
-- SELECT column_name, data_type FROM information_schema.columns 
-- WHERE table_name='messages' AND column_name='read_at';

-- Count messages with and without read_at:
-- SELECT 
--   COUNT(*) as total_messages,
--   COUNT(CASE WHEN read_at IS NOT NULL THEN 1 END) as read_messages,
--   COUNT(CASE WHEN read_at IS NULL THEN 1 END) as unread_messages
-- FROM messages;

-- Check indexes were created:
-- SELECT indexname FROM pg_indexes WHERE tablename='messages';