-- Migration 109: Create read_receipts table (v0.502 CH1-01)
CREATE TABLE IF NOT EXISTS read_receipts (
    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
    user_id UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
    message_id UUID NOT NULL REFERENCES messages(id) ON DELETE CASCADE,
    read_at TIMESTAMP WITH TIME ZONE DEFAULT NOW(),
    CONSTRAINT uq_read_receipts_user_message UNIQUE (user_id, message_id)
);
CREATE INDEX idx_read_receipts_message_id ON read_receipts(message_id);
CREATE INDEX idx_read_receipts_user_id ON read_receipts(user_id);