微信小程序页面迁移校验之前 P5任务处理之前

apps/backend/app/ai/cache_service.py

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+"""
+AI 缓存读写服务。
+
+负责 biz.ai_cache 表的 CRUD 和保留策略管理。
+所有查询和写入操作强制 site_id 隔离。
+"""
+
+from __future__ import annotations
+
+import json
+import logging
+from datetime import datetime
+
+from app.database import get_connection
+
+logger = logging.getLogger(__name__)
+
+
+class AICacheService:
+    """AI 缓存读写服务。"""
+
+    def get_latest(
+        self,
+        cache_type: str,
+        site_id: int,
+        target_id: str,
+    ) -> dict | None:
+        """查询最新缓存记录。
+
+        按 (cache_type, site_id, target_id) 查询 created_at 最新的一条。
+        无记录时返回 None。
+        """
+        conn = get_connection()
+        try:
+            with conn.cursor() as cur:
+                cur.execute(
+                    """
+                    SELECT id, cache_type, site_id, target_id,
+                           result_json, score, triggered_by,
+                           created_at, expires_at
+                    FROM biz.ai_cache
+                    WHERE cache_type = %s AND site_id = %s AND target_id = %s
+                    ORDER BY created_at DESC
+                    LIMIT 1
+                    """,
+                    (cache_type, site_id, target_id),
+                )
+                columns = [desc[0] for desc in cur.description]
+                row = cur.fetchone()
+                if row is None:
+                    return None
+                return _row_to_dict(columns, row)
+        finally:
+            conn.close()
+
+    def get_history(
+        self,
+        cache_type: str,
+        site_id: int,
+        target_id: str,
+        limit: int = 2,
+    ) -> list[dict]:
+        """查询历史缓存记录（按 created_at DESC），用于 Prompt reference。
+
+        无记录时返回空列表。
+        """
+        conn = get_connection()
+        try:
+            with conn.cursor() as cur:
+                cur.execute(
+                    """
+                    SELECT id, cache_type, site_id, target_id,
+                           result_json, score, triggered_by,
+                           created_at, expires_at
+                    FROM biz.ai_cache
+                    WHERE cache_type = %s AND site_id = %s AND target_id = %s
+                    ORDER BY created_at DESC
+                    LIMIT %s
+                    """,
+                    (cache_type, site_id, target_id, limit),
+                )
+                columns = [desc[0] for desc in cur.description]
+                rows = cur.fetchall()
+                return [_row_to_dict(columns, row) for row in rows]
+        finally:
+            conn.close()
+
+    def write_cache(
+        self,
+        cache_type: str,
+        site_id: int,
+        target_id: str,
+        result_json: dict,
+        triggered_by: str | None = None,
+        score: int | None = None,
+        expires_at: datetime | None = None,
+    ) -> int:
+        """写入缓存记录，返回 id。写入后清理超限记录。"""
+        conn = get_connection()
+        try:
+            with conn.cursor() as cur:
+                cur.execute(
+                    """
+                    INSERT INTO biz.ai_cache
+                        (cache_type, site_id, target_id, result_json,
+                         triggered_by, score, expires_at)
+                    VALUES (%s, %s, %s, %s, %s, %s, %s)
+                    RETURNING id
+                    """,
+                    (
+                        cache_type,
+                        site_id,
+                        target_id,
+                        json.dumps(result_json, ensure_ascii=False),
+                        triggered_by,
+                        score,
+                        expires_at,
+                    ),
+                )
+                row = cur.fetchone()
+                conn.commit()
+                cache_id: int = row[0]
+        except Exception:
+            conn.rollback()
+            raise
+        finally:
+            conn.close()
+
+        # 写入成功后清理超限记录（失败仅记录警告，不影响写入结果）
+        try:
+            deleted = self._cleanup_excess(cache_type, site_id, target_id)
+            if deleted > 0:
+                logger.info(
+                    "清理超限缓存: cache_type=%s site_id=%s target_id=%s 删除=%d",
+                    cache_type, site_id, target_id, deleted,
+                )
+        except Exception:
+            logger.warning(
+                "清理超限缓存失败: cache_type=%s site_id=%s target_id=%s",
+                cache_type, site_id, target_id,
+                exc_info=True,
+            )
+
+        return cache_id
+
+    def _cleanup_excess(
+        self,
+        cache_type: str,
+        site_id: int,
+        target_id: str,
+        max_count: int = 500,
+    ) -> int:
+        """清理超限记录，保留最近 max_count 条，返回删除数量。"""
+        conn = get_connection()
+        try:
+            with conn.cursor() as cur:
+                # 删除超出保留上限的最旧记录
+                cur.execute(
+                    """
+                    DELETE FROM biz.ai_cache
+                    WHERE id IN (
+                        SELECT id FROM biz.ai_cache
+                        WHERE cache_type = %s AND site_id = %s AND target_id = %s
+                        ORDER BY created_at DESC
+                        OFFSET %s
+                    )
+                    """,
+                    (cache_type, site_id, target_id, max_count),
+                )
+                deleted = cur.rowcount
+                conn.commit()
+                return deleted
+        except Exception:
+            conn.rollback()
+            raise
+        finally:
+            conn.close()
+
+
+def _row_to_dict(columns: list[str], row: tuple) -> dict:
+    """将数据库行转换为 dict，处理特殊类型序列化。"""
+    result = {}
+    for col, val in zip(columns, row):
+        if isinstance(val, datetime):
+            result[col] = val.isoformat()
+        else:
+            result[col] = val
+    return result