feat(subscribe): accumulate music album track progress

database/versions/c8e4a1f7b2d6_3_0_39.py

@@ -0,0 +1,39 @@
+"""3.0.39 专辑订阅记录已接受资源中的音轨事实。"""
+
+import sqlalchemy as sa
+from alembic import op
+
+revision = "c8e4a1f7b2d6"
+down_revision = "b7d1e4a9c206"
+branch_labels = None
+depends_on = None
+
+_TABLE = "subscribe"
+_COLUMN = "downloaded_tracks"
+
+
+def _table_exists(connection) -> bool:
+    """判断订阅表是否已经由基础模型创建。"""
+    return _TABLE in sa.inspect(connection).get_table_names()
+
+
+def _column_names(connection) -> set[str]:
+    """读取订阅表现有列名，兼容表尚未创建或模型已包含当前列的场景。"""
+    inspector = sa.inspect(connection)
+    if not _table_exists(connection):
+        return set()
+    return {column["name"] for column in inspector.get_columns(_TABLE)}
+
+
+def upgrade() -> None:
+    """增加专辑分批下载所需的音轨事实列，旧订阅从空事实开始累计。"""
+    connection = op.get_bind()
+    if _table_exists(connection) and _COLUMN not in _column_names(connection):
+        op.add_column(_TABLE, sa.Column(_COLUMN, sa.JSON(), nullable=True))
+
+
+def downgrade() -> None:
+    """删除专辑音轨事实列，回退后活动订阅进度将丢失。"""
+    connection = op.get_bind()
+    if _table_exists(connection) and _COLUMN in _column_names(connection):
+        op.drop_column(_TABLE, _COLUMN)