"""attachments are kept once: inside their message

An attachment used to be stored twice — inside the raw message blob, and again
as a blob of its own. Now only the raw message is kept; ``part_index`` says
which MIME part of it (its position in a walk of the message) holds the
attachment, so it can be taken out when downloaded. ``blob_sha256`` stays: the
attachment's content hash, which names its thumbnail and checks what is taken
out. Rows stored before this have no index; they are found by that hash.

Existing separate copies are removed by a background pass on the worker
(app/indexer/attachments.py ``dedupe_existing``), only after checking each one
can be taken out of its message again.

Revision ID: 0023
Revises: 0022
Create Date: 2026-10-08
"""

from __future__ import annotations

from collections.abc import Sequence

from alembic import op

revision: str = "0023"
down_revision: str | None = "0022"
branch_labels: str | Sequence[str] | None = None
depends_on: str | Sequence[str] | None = None


def upgrade() -> None:
    op.execute("ALTER TABLE attachments ADD COLUMN part_index integer")


def downgrade() -> None:
    op.execute("ALTER TABLE attachments DROP COLUMN IF EXISTS part_index")