Joh*_*ner 5 sql-server datafile
我正在寻找一种方法来有效地识别最靠近物体结束一个的SQL Server的数据文件。这种方法需要对大型数据文件保持高性能。
下面的查询使用一个未公开的动态管理功能是随2012 SQL：sys.dm_db_database_page_allocations; 此 DMF 提供了与DBCC IND命令的粗略等效项。
以下查询标识给定数据文件中的最后一个对象（警告：不要对大于 25 GB 的数据库运行此查询，除非您想在某个时候取消它）：
-- Return object with highest Extent Page ID
SELECT files.name as logical_file_name
, files.physical_name as physical_file_name
, OBJECT_SCHEMA_NAME(object_id) + N'.' + OBJECT_NAME(object_id) AS object_name
, alloc.*
FROM sys.dm_db_database_page_allocations(DB_ID(), NULL, NULL, NULL, NULL) alloc
INNER JOIN sys.database_files files
ON alloc.extent_file_id = files.file_id
WHERE is_allocated = 1
AND files.name = 'Logical_FileName'
ORDER BY files.name , files.physical_name, extent_page_id DESC
正如上面的警告所暗示的那样，这个查询会随着数据库大小的增加而运行得更慢，因为该函数实际上是为查看特定对象而不是查看特定数据文件而设计的有针对性的方法。当NULL像我一样传入参数时，这个函数可能会在后台遍历数据库中的所有对象并输出组合输出。这完成了我所需要的，但它以一种不适合优化的非常暴力的方式完成。
我希望有一种方法可以遍历GAM、SGAM和/或IAM 链，以快速识别给定数据文件末尾的对象。我假设我必须将 TSQL 之外的这种方法推到 PowerShell 之类的东西上，然后回到使用DBCC PAGE调用或类似性质的东西，遍历页面分配映射以查找给定数据文件的最后一个对象是什么。...我希望有人已经把这些代码放在一起，或者比我更了解这些结构和/或这些未记录程序的输出。
这是许多人会问的不可避免的问题，所以我将直接回答它。我一直在从事的项目是使遗留系统加快速度，但是在将一堆堆表合并在一起之后（由于其他原因这是一场噩梦），我现在在我的数据中留下了一堆可用空间文件。我想将此空间释放回操作系统，但是，将对象迁移到不同数据文件的传统方法在此阶段不可行，因为我没有足够的可用空间在系统上使用（直到我能够从此数据文件中释放更多空间）。
我已经禁用文件增长并DBCC SHRINKFILE TRUNCATEONLY每晚运行一个命令来释放数据文件末尾的任何打开页面，但这是一个缓慢而艰巨的过程，可能会经常工作，但不会经常工作。我希望确定文件末尾的对象是什么，以便我可以手动重建它们并在更快的时间表内释放空间。
有没有办法快速识别位于给定数据文件末尾的对象的名称？我现在采用的方法不能满足我的需求，我愿意使用任何可用的方法。
我想这样就可以了。这段代码基本上做了以下事情：
DBCC SHRINKFILE命令，仅将文件末尾的剩余空白释放回操作系统（应该是立即的），并且实际上相当于DBCC SHRINKFILE使用TRUNCATEONLY它嵌套在一个游标中，该游标迭代数据库中数据文件的页面 ID，并根据我的本地化测试快速执行。我还添加了识别数据文件末尾是否被表或索引未保留的页面（例如 IAM 或 PFS 页面）占用的功能。
SET NOCOUNT ON;
-- Create Temp Table to push DBCC PAGE results into
CREATE TABLE #dbccPage_output(
ID INT IDENTITY(1,1)
, [ParentObject] VARCHAR(255)
, [Object] VARCHAR(255)
, [Field] VARCHAR(255)
, [Value] VARCHAR(255)
)
GO
-- Variables to hold pointer information for traversing GAM and SGAM pages
DECLARE @GAM_maxPageID INT, @SGAM_maxPageID INT, @maxPageID INT,
@GAM_page INT, @SGAM_page INT
DECLARE @stmt VARCHAR(2000)
-- Final Output Table
DECLARE @myOutputTable TABLE
(
LogicalFileName VARCHAR(255)
, ObjectID BIGINT
, IndexID BIGINT
, PartitionID BIGINT
, MaxPageID BIGINT
)
-- Cursor to iterate through each file
DECLARE cursorFileIds CURSOR
FOR
SELECT file_id, size
FROM sys.database_files
WHERE type = 0
-- Variable to hold fileID
DECLARE @fileID INT, @size INT, @interval INT
-- Inject the data into the cursor
OPEN cursorFileIds
FETCH NEXT FROM cursorFileIds
INTO @fileID, @size
-- Enter the While Loop. This loop will end when the
-- end of the data injected into the cursor is reached.
WHILE @@FETCH_STATUS = 0
BEGIN
-- Truncate table (mainly used for 2nd pass and forward)
TRUNCATE TABLE #dbccPage_output
-- Referenced if we need to step back a GAM/SGAM interval
STEPBACK:
-- # of pages in a GAM interval
SET @interval = @size / 511232
-- Set GAM Page to read
SET @GAM_page = CASE @interval WHEN 0 THEN 2 ELSE @interval * 511232 END
-- Set SGAM page to read (always the next page after the GAM)
SET @SGAM_page = CASE @interval WHEN 0 THEN 3 ELSE (@interval * 511232) + 1 END
-- Search Last GAM Interval page
SET @stmt = 'DBCC PAGE(0, ' + CAST(@fileID AS VARCHAR(10)) + ', ' + CAST(@GAM_page AS VARCHAR(20)) + ', 3) WITH TABLERESULTS, NO_INFOMSGS' -- GAM on Primary Datafile
PRINT @stmt
INSERT INTO #dbccPage_output ([ParentObject], [Object], [Field], [Value])
EXEC (@stmt)
-- Get Last Allocated Page Number
SELECT TOP 1
@GAM_maxPageID = REVERSE(SUBSTRING(REVERSE(Field), CHARINDEX(')', REVERSE(Field)) + 1, CHARINDEX(':', REVERSE(Field)) - CHARINDEX(')', REVERSE(Field)) - 1))
FROM #dbccPage_output
WHERE [Value] = ' ALLOCATED'
ORDER BY ID DESC
-- Truncate Table
TRUNCATE TABLE #dbccPage_output
-- Search Last SGAM Interval page
SET @stmt = 'DBCC PAGE(0, ' + CAST(@fileID AS VARCHAR(10)) + ', ' + CAST(@SGAM_page AS VARCHAR(20)) + ', 3) WITH TABLERESULTS, NO_INFOMSGS' -- SGAM on Primary Datafile
PRINT @stmt
INSERT INTO #dbccPage_output ([ParentObject], [Object], [Field], [Value])
EXEC (@stmt)
-- Get Last Allocated Page Number
SELECT TOP 1
@SGAM_maxPageID = REVERSE(SUBSTRING(REVERSE(Field), CHARINDEX(')', REVERSE(Field)) + 1, CHARINDEX(':', REVERSE(Field)) - CHARINDEX(')', REVERSE(Field)) - 1))
FROM #dbccPage_output
WHERE [Value] = ' ALLOCATED'
ORDER BY ID DESC
-- Get highest page value between SGAM and GAM
SELECT @maxPageID = MAX(t.value)
FROM (VALUES (@GAM_maxPageID), (@SGAM_maxPageID)) t(value)
TRUNCATE TABLE #dbccPage_output
-- Check if GAM or SGAM is last allocated page in the chain, if so, step back one interval
IF(@maxPageID IN (@GAM_page, @SGAM_page))
BEGIN
SET @size = ABS(@size - 511232)
GOTO STEPBACK
END
-- Search Highest Page Number of Data File
SET @stmt = 'DBCC PAGE(0, ' + CAST(@fileID AS VARCHAR(10)) + ', ' + CAST(CASE WHEN @maxPageID = @SGAM_maxPageID THEN @maxPageID + 7 ELSE @maxPageID END AS VARCHAR(50)) + ', 1) WITH TABLERESULTS, NO_INFOMSGS' -- Page ID of Last Allocated Object
PRINT @stmt
INSERT INTO #dbccPage_output ([ParentObject], [Object], [Field], [Value])
EXEC (@stmt)
-- Capture Object Name of DataFile
INSERT INTO @myOutputTable
SELECT (SELECT name FROM sys.database_files WHERE file_id = @fileID) AS LogicalFileName
, CASE WHEN (SELECT [Value] FROM #dbccPage_output WHERE Field = 'm_type') IN ('1', '2') THEN -- If page type is data or index
CAST((SELECT [Value] FROM #dbccPage_output WHERE Field = 'Metadata: ObjectId') AS BIGINT)
ELSE CAST((SELECT [Value] FROM #dbccPage_output WHERE Field = 'm_type') AS BIGINT)
END AS ObjectID
, NULLIF(CAST((SELECT [Value] FROM #dbccPage_output WHERE Field = 'Metadata: IndexId') AS BIGINT), -1) AS IndexID
, NULLIF(CAST((SELECT [Value] FROM #dbccPage_output WHERE Field = 'Metadata: PartitionId') AS BIGINT), 0) AS PartitionID
, @maxPageID + 7 AS MaxPageID
-- Reset Max Page Values
SELECT @GAM_maxPageID = 0, @SGAM_maxPageID = 0, @maxPageID = 0
-- Traverse the Data in the cursor
FETCH NEXT FROM cursorFileIds
INTO @fileID, @size
END
-- Close and deallocate the cursor because you've finished traversing all it's data
CLOSE cursorFileIds
DEALLOCATE cursorFileIds
-- page type values pt. 1: https://www.sqlskills.com/blogs/paul/inside-the-storage-engine-using-dbcc-page-and-dbcc-ind-to-find-out-if-page-splits-ever-roll-back/
-- page type values pt. 2: https://www.sqlskills.com/blogs/paul/inside-the-storage-engine-anatomy-of-a-page/
-- ObjectIDs of either 0 or 99: https://www.sqlskills.com/blogs/paul/finding-table-name-page-id/
-- Output Object Closest to the End
SELECT t.LogicalFileName
, CAST(CASE WHEN t.IndexID IS NULL THEN
CASE t.ObjectID
WHEN 0 THEN '>>No MetaData Found<<' -- This isn't m_type, rather ObjectID
WHEN 1 THEN '>>Data Page<<'
WHEN 2 THEN '>>Index Page<<'
WHEN 3 THEN '>>Text Mix Page<<'
WHEN 4 THEN '>>Text Tree Page<<'
WHEN 6 THEN '>>DCM Page<<<'
WHEN 7 THEN '>>Sort Page<<'
WHEN 8 THEN '>>GAM Page<<'
WHEN 9 THEN '>>SGAM Page<<'
WHEN 10 THEN '>>IAM Page<<'
WHEN 11 THEN '>>PFS Page<<'
WHEN 13 THEN '>>Boot Page<<'
WHEN 15 THEN '>>File Header Page<<'
WHEN 16 THEN '>>Diff Map Page<<'
WHEN 17 THEN '>>ML Map Page<<'
WHEN 18 THEN '>>Deallocated DBCC CHECKDB Repair Page<<'
WHEN 19 THEN '>>Temporary ALTER INDEX Page<<'
WHEN 20 THEN '>>Pre-Allocated BULK LOAD Page<<'
WHEN 99 THEN '>>Possible Page Corruption/Run DBCC CHECKDB<<' -- This isn't m_type, rather ObjectID
ELSE CAST(t.ObjectID AS VARCHAR(50))
END
ELSE QUOTENAME(OBJECT_SCHEMA_NAME(t.ObjectID)) + '.' + QUOTENAME(OBJECT_NAME(t.ObjectID)) END AS VARCHAR(250)) AS TableName
, QUOTENAME(i.name) AS IndexName
, p.partition_number AS PartitionNumber
, 'DBCC SHRINKFILE(' + t.LogicalFileName + ', ' + CAST(CEILING((t.MaxPageID + 8) * 0.0078125) AS VARCHAR(50)) + ')' AS ShrinkCommand_Explicit
, 'DBCC SHRINKFILE(' + t.LogicalFileName + ', TRUNCATEONLY)' AS ShrinkCommand_TRUNCATEONLY
FROM @myOutputTable t
LEFT JOIN sys.indexes i
ON t.ObjectID = i.object_id
AND t.IndexID = i.index_id
LEFT JOIN sys.partitions p
ON t.ObjectID = p.object_id
AND t.PartitionID = p.partition_id
-- Cleanup
DROP TABLE #dbccPage_output
GO
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