"""Separate scanner membership from retained history

Revision ID: 035
Revises: 034
Create Date: 2026-09-07 00:00:00.000000

Migration 032 stopped ``delete_ticker`` and the delisting path from destroying
history, but left the other half of the problem open — its own comment said so:
"Pruning a symbol that is merely no longer an index constituent still destroys
history; that needs a tracked/membership state separate from delisting."

``bootstrap_universe(prune_missing=True)`` still ran ``DELETE FROM tickers``,
cascading OHLCV, setups and scores away for any symbol that had merely dropped
out of the index. The survivorship audit measured what that costs: restoring 85
removed constituents moved the same window from 2.09 Sharpe / 51.6% CAGR to
1.57 / 38.1%. A prune that deletes is how a universe silently becomes the
survivors.

``untracked_on`` is the sibling of ``delisted_on``, and the distinction is the
point:

  delisted_on   the security stopped trading
  untracked_on  it still trades; we stopped scanning it

Both retain every row. NULL in both means "in the live path" — ``active_only``
filters on both, so scanning, ranking, scoring, breadth and ingestion skip an
untracked name, while the backtest's universe query deliberately does not, so
today's membership cannot erase yesterday's candidates.

Nullable and reversible: a symbol that returns to the index has ``untracked_on``
cleared by the next bootstrap and rejoins the live path with its history intact.
"""
from typing import Sequence, Union

from alembic import op
import sqlalchemy as sa


revision: str = "035"
down_revision: Union[str, None] = "034"
branch_labels: Union[str, Sequence[str], None] = None
depends_on: Union[str, Sequence[str], None] = None


def upgrade() -> None:
    op.add_column("tickers", sa.Column("untracked_on", sa.Date(), nullable=True))
    # Same reasoning as ix_tickers_delisted_on: the live path tests this
    # predicate on every universe scan, and untracked rows accumulate.
    op.create_index("ix_tickers_untracked_on", "tickers", ["untracked_on"])


def downgrade() -> None:
    # Dropping the column re-admits every untracked symbol to the live path.
    # The rows and their history survive either way; that is the whole point.
    op.drop_index("ix_tickers_untracked_on", table_name="tickers")
    op.drop_column("tickers", "untracked_on")