"""drop dead storage_objects.parent_object_id column and idx_storage_parent

Revision ID: f7a8b9c0d1e2
Revises: e1f2a3b4c5d6
Create Date: 2026-08-21

Removes a never-written column and its orphaned index. Tree structure is
maintained entirely via relative_path (materialized path); see
backend/src/backend/scripts.py (list_workspace_tree / list_workspace_directories).

MySQL 8.0 does not support DROP INDEX IF EXISTS / DROP COLUMN IF EXISTS,
so the calls below are unconditional.
"""

from collections.abc import Sequence

import sqlalchemy as sa
from alembic import op
from sqlalchemy.dialects import mysql

# revision identifiers, used by Alembic.
revision: str = "f7a8b9c0d1e2"
down_revision: str | Sequence[str] | None = "e1f2a3b4c5d6"
branch_labels: str | Sequence[str] | None = None
depends_on: str | Sequence[str] | None = None


def upgrade() -> None:
    """Drop the dead index, then the dead column."""
    op.drop_index("idx_storage_parent", table_name="storage_objects")
    op.drop_column("storage_objects", "parent_object_id")
    # Refresh the table comment so the warning reaches the DB, not just the ORM.
    op.execute(
        "ALTER TABLE storage_objects "
        "COMMENT = 'Workspace 文件和 RustFS 对象的统一元数据;"
        "目录树走 materialized path (relative_path),"
        "不要 join 邻接表列——已删除。'"
    )


def downgrade() -> None:
    """Recreate the column and index for rollback."""
    op.add_column(
        "storage_objects",
        sa.Column("parent_object_id", mysql.CHAR(length=26), nullable=True),
    )
    op.create_index(
        "idx_storage_parent",
        "storage_objects",
        ["parent_object_id"],
        unique=False,
    )
    op.execute(
        "ALTER TABLE storage_objects "
        "COMMENT = 'Workspace 文件和 RustFS 对象的统一元数据'"
    )