完善数据层慢SQL观测与消息查询优化

- 为数据库公共层增加慢 SQL 阈值配置与统一耗时日志记录

- 为消息表补充群成员回溯、群类型过滤和待处理媒体扫描等关键索引

- 将多处按日期查询改为时间范围查询，减少 DATE(timestamp) 导致的索引失效

- 修正消息存储层重复定义的日期范围方法，并更新工程优化文档中的 7.4 当前进展

db/base.py

@@ -1,4 +1,6 @@
 # -*- coding: utf-8 -*-
+import time
+
 from loguru import logger
 from typing import List, Dict, Any, Optional, Tuple, Union
 
@@ -12,19 +14,62 @@ class BaseDBOperator:
         self.db_manager = db_manager
         self.LOG = logger
 
+    @staticmethod
+    def _compact_sql(sql: str) -> str:
+        """把 SQL 压成单行，便于日志里快速定位问题。"""
+        return " ".join(str(sql or "").split())
+
+    @classmethod
+    def _truncate_text(cls, value, max_length: int = 240) -> str:
+        """截断长文本，避免日志被超长 SQL 或参数刷屏。"""
+        text = str(value or "")
+        if len(text) <= max_length:
+            return text
+        return f"{text[:max_length]}..."
+
+    def _log_sql_timing(self, operation: str, sql: str, params, elapsed_ms: float, affected_rows: Optional[int] = None) -> None:
+        """记录慢 SQL 日志。
+
+        设计说明：
+        1. 只在超过阈值时输出 warning，避免日常日志噪声过大；
+        2. 统一输出压缩后的 SQL 与截断参数，便于线上排查具体慢点；
+        3. 查询/更新/批量/事务都走同一入口，后续如果要接后台审计也更容易扩展。
+        """
+        if not self.db_manager.is_slow_query_log_enabled():
+            return
+
+        threshold_ms = self.db_manager.get_slow_query_threshold_ms()
+        if elapsed_ms < threshold_ms:
+            return
+
+        affected_text = ""
+        if affected_rows is not None:
+            affected_text = f" affected_rows={affected_rows}"
+        self.LOG.warning(
+            f"检测到慢SQL operation={operation} cost_ms={round(elapsed_ms, 2)} threshold_ms={threshold_ms}"
+            f"{affected_text} sql={self._truncate_text(self._compact_sql(sql), 400)} "
+            f"params={self._truncate_text(params, 240)}"
+        )
+
     def execute_query(self, sql: str, params: Optional[tuple] = None, fetch_one: bool = False) -> Union[
         List[Dict], Dict, None]:
         """执行查询SQL"""
         conn = self.db_manager.get_mysql_connection()
+        started_at = time.perf_counter()
         try:
             with conn.cursor(dictionary=True) as cursor:
                 cursor.execute(sql, params or ())
+                elapsed_ms = (time.perf_counter() - started_at) * 1000
                 if fetch_one:
-                    return cursor.fetchone()
-                return cursor.fetchall()
+                    result = cursor.fetchone()
+                    self._log_sql_timing("query_one", sql, params, elapsed_ms, 1 if result else 0)
+                    return result
+                result = cursor.fetchall()
+                self._log_sql_timing("query", sql, params, elapsed_ms, len(result or []))
+                return result
         except Exception as e:
             self.LOG.error(
-                f"执行更新SQL出错: {e}, SQL: {sql}, 参数: {str(params)[:200] + '...' if len(str(params)) > 200 else params}"
+                f"执行查询SQL出错: {e}, SQL: {sql}, 参数: {str(params)[:200] + '...' if len(str(params)) > 200 else params}"
             )
             return None
         finally:
@@ -33,10 +78,13 @@ class BaseDBOperator:
     def execute_update(self, sql: str, params: Optional[tuple] = None) -> bool:
         """执行更新SQL"""
         conn = self.db_manager.get_mysql_connection()
+        started_at = time.perf_counter()
         try:
             with conn.cursor() as cursor:
                 cursor.execute(sql, params or ())
+                affected_rows = cursor.rowcount
             conn.commit()
+            self._log_sql_timing("update", sql, params, (time.perf_counter() - started_at) * 1000, affected_rows)
             return True
         except Exception as e:
             self.LOG.error(
@@ -53,10 +101,19 @@ class BaseDBOperator:
             return True
 
         conn = self.db_manager.get_mysql_connection()
+        started_at = time.perf_counter()
         try:
             with conn.cursor() as cursor:
                 cursor.executemany(sql, params_list)
+                affected_rows = cursor.rowcount
             conn.commit()
+            self._log_sql_timing(
+                "batch_update",
+                sql,
+                f"params_count={len(params_list)}",
+                (time.perf_counter() - started_at) * 1000,
+                affected_rows,
+            )
             return True
         except Exception as e:
             self.LOG.error(f"批量执行SQL出错: {e}, SQL: {sql}, 参数数量: {len(params_list)}")
@@ -71,11 +128,18 @@ class BaseDBOperator:
             return True
 
         conn = self.db_manager.get_mysql_connection()
+        started_at = time.perf_counter()
         try:
             with conn.cursor() as cursor:
                 for sql, params in operations:
                     cursor.execute(sql, params)
             conn.commit()
+            self._log_sql_timing(
+                "transaction",
+                f"{len(operations)} statements",
+                f"operations={len(operations)}",
+                (time.perf_counter() - started_at) * 1000,
+            )
             return True
         except Exception as e:
             self.LOG.error(f"执行事务出错: {e}, 操作数量: {len(operations)}")