"""worker_lane.autoscale — may this lane grow itself?

Milestone 422 step 7. One boolean, defaulting FALSE on every existing row and
on every new one.

## Why the default is false and not "sensible"

This is the only part of the milestone that acts without anyone watching. The
manual dial (step 4) and the reconcile (step 3) both do exactly what someone
asked for; this one decides. Shipping it on would mean every install starts
with a process that changes its own resource usage based on a heuristic tuned
against nobody's workload.

Off also makes the failure mode benign: if the signal is wrong, nothing
happens until an operator opts a lane in, and they opted in while watching.

## Why per lane and not one global switch

The lanes are not alike in what a slot costs. A `worker` slot is a process;
an `ml` slot is another copy of a ~3.5GB model. A global switch would enable
growth on a lane whose behaviour under load nobody has observed, and the one
it would hurt most is the one whose cost is least visible.

Revision ID: 0104
Revises: 0103
Create Date: 2026-09-22

"""
from typing import Sequence, Union

import sqlalchemy as sa
from alembic import op

revision: str = "0104"
down_revision: Union[str, None] = "0103"
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


def upgrade() -> None:
    op.add_column(
        "worker_lane",
        sa.Column(
            "autoscale", sa.Boolean(),
            server_default=sa.text("false"), nullable=False,
        ),
    )


def downgrade() -> None:
    op.drop_column("worker_lane", "autoscale")