perf: 优化 MySQL 查询并接入 pytest

web/backend/migrations/versions/20260830_0031_mysql_task_query_indexes.py

@@ -0,0 +1,52 @@
+"""Add composite indexes for task polling, ordering, and retention queries.
+
+Revision ID: 20260830_0031
+Revises: 20260829_0030
+Create Date: 2026-08-30
+"""
+
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+revision: str = "20260830_0031"
+down_revision: Union[str, None] = "20260829_0030"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+INDEXES = (
+    # /api/douyu/tasks filters by scope and returns the newest rows first.
+    ("ix_douyu_tasks_handbook_scope_id", "douyu_tasks", ["handbook_scope", "id"]),
+    # The legacy compatibility branch also filters by task_type.
+    (
+        "ix_douyu_tasks_handbook_scope_task_type_id",
+        "douyu_tasks",
+        ["handbook_scope", "task_type", "id"],
+    ),
+    # Supports terminal-task retention and finished-time ordered Cookie views.
+    ("ix_douyu_tasks_status_finished_at_id", "douyu_tasks", ["status", "finished_at", "id"]),
+    ("ix_login_tasks_status_finished_at_id", "login_tasks", ["status", "finished_at", "id"]),
+)
+
+
+def _indexes(bind, table_name: str) -> set[str]:
+    if not sa.inspect(bind).has_table(table_name):
+        return set()
+    return {index["name"] for index in sa.inspect(bind).get_indexes(table_name)}
+
+
+def upgrade() -> None:
+    bind = op.get_bind()
+    for name, table_name, columns in INDEXES:
+        if name not in _indexes(bind, table_name):
+            op.create_index(name, table_name, columns)
+
+
+def downgrade() -> None:
+    bind = op.get_bind()
+    for name, table_name, _ in reversed(INDEXES):
+        if name in _indexes(bind, table_name):
+            op.drop_index(name, table_name=table_name)