"""index messages(user_id, message_id_hdr)

Speeds the per-user Message-ID lookups used by JWZ threading (§7.2 candidate
set) and by the duplicate-Message-ID resolution in the indexer (§7.1).

Revision ID: 0002
Revises: 0001
Create Date: 2026-07-17
"""

from __future__ import annotations

from collections.abc import Sequence

from alembic import op

revision: str = "0002"
down_revision: str | None = "0001"
branch_labels: str | Sequence[str] | None = None
depends_on: str | Sequence[str] | None = None


def upgrade() -> None:
    op.execute("CREATE INDEX ix_messages_user_msgid ON messages (user_id, message_id_hdr)")


def downgrade() -> None:
    op.execute("DROP INDEX IF EXISTS ix_messages_user_msgid")