在 SQL Server 2014 中，带有 TABLOCK 提示的 INSERT 语句可以在完全恢复模式下最少记录，为什么？

Question

来自微软 Understanding Minimally Logged Operations

Minimally logged operations are available only if your database is in bulk-logged or simple recovery mode.

下面的代码解释了我所看到的。

use master;

IF DB_ID('RecoveryETL') IS NOT NULL
BEGIN
    ALTER DATABASE RecoveryETL SET SINGLE_USER WITH ROLLBACK IMMEDIATE 
    DROP DATABASE RecoveryETL;
END

--Create sample database for testing
CREATE DATABASE RecoveryETL 
ON PRIMARY
    (NAME = N'RecoveryETL_Date', FILENAME = N'C:\SQLDATA\RecoveryETL_Data.Mdf', SIZE = 1024MB, MAXSIZE = UNLIMITED, FILEGROWTH = 50MB)
LOG ON
    (NAME = N'RecoveryETL_Log', FILENAME = N'C:\SQLDATA\RecoveryETL_Log.LDF', SIZE = 100MB, MAXSIZE = 1024MB, FILEGROWTH = 25MB)
GO

--Set Recovery Mode to Full
ALTER DATABASE RecoveryETL SET RECOVERY FULL ;
GO

USE RecoveryETL;
GO

--Immediately perform a full backup otherwise database will remain in simple mode
BACKUP DATABASE RecoveryETL
TO DISK = 'C:\Database Backups\RecoveryETL_1.bak'
WITH RETAINDAYS = 90 
, FORMAT
, INIT
, MEDIANAME = 'RecoveryETL'
, NAME = 'RecoveryETL-Full Database Backup'
, COMPRESSION ;
GO

--Create a Testing Table
IF OBJECT_ID('dbo.HeapTable') IS NOT NULL 
DROP TABLE dbo.HeapTable

CREATE TABLE HeapTable
(
    Fld1 INT, 
    Fld2 INT, 
    FId3 INT,
    ModDate Datetime
)

--Insert Records W/O TABLOCK hint
INSERT INTO HeapTable (Fld1, Fld2, FId3, ModDate)
    SELECT TOP 10000 
        SalesOrderDetailID, SalesOrderDetailID + 100, SalesOrderDetailID + 99, GETDATE()
    FROM 
        AdventureWorks2012.Sales.SalesOrderDetail

--Is it minimum logged? No, more than 10,000 log records
SELECT * 
FROM sys.fn_dblog(null, null)
WHERE AllocUnitName LIKE '%HeapTable%' 

--Truncate logs
CHECKPOINT;

BACKUP LOG RecoveryETL
TO DISK = 'NULL'
WITH RETAINDAYS = 90
, NOINIT
, MEDIANAME = 'RecoveryETL'
, NAME = 'RecoveryETL-Log Backup'
, COMPRESSION ;
GO

--Make sure logs are gone
SELECT * 
FROM sys.fn_dblog(null, null)
WHERE AllocUnitName LIKE '%HeapTable%' 

--Insert records WITH TABLOCK hint
INSERT INTO HeapTable WITH(TABLOCK)(Fld1, Fld2, FId3, ModDate)
    SELECT TOP 10000 
        SalesOrderDetailID, SalesOrderDetailID + 100, SalesOrderDetailID + 99, GETDATE()
    FROM 
        AdventureWorks2012.Sales.SalesOrderDetail

--Minimum logged here!!!!!
SELECT * 
FROM sys.fn_dblog(null, null)
WHERE AllocUnitName LIKE '%HeapTable%'

我还尝试使用具有最少日志记录的日志备份来恢复数据库时间点，正如预期的那样，我无法使数据库脱离恢复状态，我可以说它们确实是最小日志记录。官方文档不准确？

Answer 1

where I can say they are truly minimum logged. The official documentation is inaccurate?

不，你错了。

是的，INSERT 的完全记录方式发生了变化，但在 full recovery model 下，即使使用 TABLOCK，它们仍然是 f完全记录.

In SQL SERVER 2005-2008 INSERT under full recovery model 是逐行记录的，所以如果你在日志文件中做了 10000 行 INSERT 你看到至少 10000 LOP_INSERT_ROW 次操作（见我的第一张照片）

现在我在 SQL SERVER 2016 上做了同样的 INSERT，首先在 BULK_LOGGED 恢复模型下，然后在 FULL 下（你可以在我的第二张图片上看到结果） .在 BULK_LOGGED 下，您可以看到仅记录了位图设置，因此操作实际上是 minimally logged。但在 FULL 恢复模式下，情况有所不同。是的，您不再看到 10000 LOP_INSERT_ROW 行，但现在您可以看到 38 个 LOP_FORMAT_PAGE 操作，并且与此操作对应的日志行是 8276 字节，即 8Kb , 一个 page。这 38 页是在 INSERT 期间格式化的整页图像，甚至在 2008 年对 INDEX REBUILD 操作也是如此。所以操作仍然是 fully logged，进入日志的信息足以完全重构操作，而不仅仅是允许回滚，就像 minimally logged 操作一样。因此，即使有 TABLOCK 提示，INSERT 进入堆仍然是 fully logged 操作，但现在它甚至是 efficiently logged 操作。在 FULL 下插入后，我什至尝试备份日志，并且在备份日志完成之前，我能够使用 stop at 从该日志中恢复。

在 SQL Server 2014 中，带有 TABLOCK 提示的 INSERT 语句可以在完全恢复模式下最少记录，为什么？

INSERT statement with TABLOCK hint can be minimum logged under full recovery mode in SQL Server 2014, why?

sql-server

database-administration

sql-server-2014