查询会话不再响应

Question

我正在尝试执行以下 T-SQL 语句：

SET NOCOUNT ON
SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED
BEGIN TRANSACTION

DECLARE @nRows INT = 1
DECLARE @DataCancellazione DATE = DATEADD(DAY, -7, GETDATE())
CREATE TABLE #IDToDel (ID BIGINT)

WHILE @nRows > 0
BEGIN
  INSERT INTO #IDToDel
  SELECT TOP 5000 LogID
  FROM MioDB.Test
  WHERE CAST(ReceivedDate AS date) < @DataCancellazione

  SELECT @nRows = @@ROWCOUNT

  DELETE RM WITH (PAGLOCK)
  FROM MioDB.Test  RM WITH (PAGLOCK)
  INNER JOIN #IDToDel TBD ON RM.LogID  = TBD.ID

  TRUNCATE TABLE #IDToDel
END
ROLLBACK

当我启动执行时，查询 window 似乎不再响应，并且进程中的 CPUTime 和 DiskIO 没有特别增加。谁能帮帮我谢谢。

Answer 1

老实说，我认为你把问题复杂化了。 SQL 服务器可以 轻松地 一次处理数百万行，我怀疑您可能会在几个 100 万行的批次中完成此操作。如果您至少有 4,000,000 行要删除，那么 5,000 行将需要 800 次迭代。

也不需要临时的table，一个DELETE可以利用一个TOP，所以你每次循环删除那么多行就可以了。我用一个变量定义它，然后传递它（1,000,000 行）。这意味着所有内容都在 4 次迭代中被删除，而不是 800 次。您可能想稍微减小大小，但我建议 500,000 是一个简单的选择。

这为您提供了以下更简洁的批处理：

SET NOCOUNT ON;
--The following transaction level seems like a terrible idea when you're performing DDL statements. Don't, just don't.
--SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED; 

DECLARE @BatchSize int = 1000000,
        @DataCancellazione date = DATEADD(DAY, -7, GETDATE());
SELECT 1; --Dataset with 1 row

WHILE @@ROWCOUNT > 0
    DELETE TOP (@BatchSize)
    FROM MioDB.Test --A Schema called "MioDB" is a little confusing
    WHERE ReceivedDate < @DataCancellazione; --Casting ReceivedDate would have had no change to the query
                                             --And could well have slowed it down.

查询会话不再响应

Query Session no longer respond

sql

tsql

sql-server