feat(migration): add missing columns to segments and conversations tables

This migration adds the columns 'audio_duration_seconds' to the 'segments' table and 'deleted_at' to the 'conversations' table, which were previously missing in the production database. The upgrade function checks for the existence of these columns and adds them if they are not present. The downgrade function allows for the removal of these columns if necessary.

api/alembic/versions/0019_backfill_missing_columns.py

@@ -0,0 +1,51 @@
+"""补建缺失列：segments.audio_duration_seconds, conversations.deleted_at
+
+0001 用 create_all 建表，对已有表不会 ALTER 追加列。
+本迁移补齐 ORM 模型中存在但生产库缺失的两列。
+
+Revision ID: 0019_backfill_missing_columns
+Revises: 0018_users_language_preference
+"""
+
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+
+from alembic import op
+
+revision: str = "0019_backfill_missing_columns"
+down_revision: Union[str, None] = "0018_users_language_preference"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def _column_names(table_name: str) -> set[str]:
+    bind = op.get_bind()
+    inspector = sa.inspect(bind)
+    return {column["name"] for column in inspector.get_columns(table_name)}
+
+
+def upgrade() -> None:
+    seg_cols = _column_names("segments")
+    if "audio_duration_seconds" not in seg_cols:
+        op.add_column(
+            "segments",
+            sa.Column("audio_duration_seconds", sa.Integer(), nullable=True),
+        )
+
+    conv_cols = _column_names("conversations")
+    if "deleted_at" not in conv_cols:
+        op.add_column(
+            "conversations",
+            sa.Column("deleted_at", sa.DateTime(timezone=True), nullable=True),
+        )
+
+
+def downgrade() -> None:
+    conv_cols = _column_names("conversations")
+    if "deleted_at" in conv_cols:
+        op.drop_column("conversations", "deleted_at")
+
+    seg_cols = _column_names("segments")
+    if "audio_duration_seconds" in seg_cols:
+        op.drop_column("segments", "audio_duration_seconds")