-- Migration 003: 1:1 DM channels.
-- channel_id is 16 bytes (UUID); member_a and member_b are identity keys in sorted order.
-- Unique on (member_a, member_b) prevents duplicate channels between the same pair.

CREATE TABLE IF NOT EXISTS channels (
    channel_id BLOB PRIMARY KEY,
    member_a   BLOB NOT NULL,
    member_b   BLOB NOT NULL,
    UNIQUE(member_a, member_b)
);

CREATE INDEX IF NOT EXISTS idx_channels_members
    ON channels(member_a, member_b);