在定義索引檢視時進行資料分割切換

當使用具索引檢視的 ALTER TABLE...SWITCH 陳述式時的條件約束

當使用 Transact-SQL ALTER TABLE...SWITCH 陳述式，在索引檢視所參考的來源與目標資料表中轉換資料子集時，資料表與索引都必須符合 使用資料分割切換有效傳送資料 中所列出的條件。請參閱該主題的資料表與索引需求章節。

如需有關移動具有已定義索引檢視的資料分割的詳細資訊，請參閱 使用資料分割切換有效傳送資料 的「移動資料分割的額外需求」一節。

使用資料分割對齊的索引檢視的典型案例，通常都是用在大型資料倉儲中。在大型資料倉儲中，一個大型的事實資料表通常會以日期進行資料分割，而彙總查詢則通常針對聯結多個維度資料表的事實資料表來執行。使用 ALTER TABLE … SWITCH 陳述式切換資料分割的移入或移出，可以提供下列好處：

• 迅速將淘汰的資料從事實資料表最舊的資料分割中封存移出。

• 迅速將新的資料從大型事實資料表的最新資料分割中移入。

下圖顯示當新的資料移入事實資料表中最新的資料分割時，資料分割對齊索引檢視的運作方式。切換到事實資料表中的新的資料分割，會攜帶在新的資料分割中所建立的彙總。

範例

下列範例顯示如何使用 ALTER TABLE … SWITCH 陳述式，將資料表中舊的資料分割切換移出，並同時帶入資料分割對齊索引檢視的一部分。

在此範例中，銷售事實資料表 [f_sales] 包含了 2006 一整年的銷售資料。這份銷售資料根據季度進行資料分割。常用查詢依日期以及依商店針對銷售金額執行彙總，而索引查詢就是用來加速在事實資料表中定義的彙總查詢的速度。現在，2006 第一季的資料已封存至封存資料表，而事實資料表中的索引查詢則維持正確以及不可用的狀態。

USE MASTER
GO

DROP DATABASE test_partition
GO

--Create database with the file groups that will be used by the partition schemes.
CREATE DATABASE test_partition
ON PRIMARY (NAME = 'paiv_Dat0', FILENAME='C:\temp\test_partition_DataFile0.mdf'),
FILEGROUP FG1 (NAME = 'paiv_Dat1', FILENAME = 'C:\temp\test_partition_DataFile1.ndf'),
FILEGROUP FG2 (NAME = 'paiv_Dat2', FILENAME = 'C:\temp\test_partition_DataFile2.ndf'),
FILEGROUP FG3 (NAME = 'paiv_Dat3', FILENAME = 'C:\temp\test_partition_DataFile3.ndf'),
FILEGROUP FG4 (NAME = 'paiv_Dat4', FILENAME = 'C:\temp\test_partition_DataFile4.ndf'),
FILEGROUP FG5 (NAME = 'paiv_Dat5', FILENAME = 'C:\temp\test_partition_DataFile5.ndf')
LOG ON (NAME = 'paiv_log', filename='C:\temp\test_partition_log.ldf')
GO
USE test_partition
GO

-- Create partition function and partition scheme.
CREATE PARTITION FUNCTION [PF1] (int)
AS RANGE LEFT FOR VALUES (20060331, 20060630, 20060930, 20061231);
GO
CREATE PARTITION SCHEME [PS1]
AS PARTITION [PF1] 
TO ([FG1], [FG2], [FG3], [FG4], [FG5]
, [PRIMARY]);
GO

-- Create fact table.
CREATE TABLE dbo.f_sales (date_key INT NOT NULL, cust_key INT, store_key INT, amt MONEY) ON PS1(date_key);
GO

-- Populate data into table f_sales. 
SET NOCOUNT ON
GO
DECLARE @d INT, @ds INT, @cs INT, @s INT
SET @d = 20060101
SET @ds = 7  -- date_key increment step

WHILE (@d <= 20061231) 
BEGIN
WHILE @d%100 > 0 AND @d%100 < 29
BEGIN
SET @cs = 10  -- # of records for customer/store for that date
SET @s = CAST ( RAND() * 1000 as INT )
WHILE (@cs > 0)
BEGIN
INSERT dbo.f_sales (date_key, cust_key, store_key, amt)
VALUES (@d, CAST ( RAND() * 1000 as INT ), @s, CAST ( RAND() * 1000 as MONEY ) )
SET @cs = @cs - 1
END
SET @d = @d + @ds
END
SET @d = @d + @ds
END
GO


-- The table with clustered index is partitioned using the partition scheme specified.
CREATE CLUSTERED INDEX UCIdx_f_sales on dbo.f_sales (date_key, cust_key, store_key) ON PS1(date_key)
GO

--Create indexed view, which aggregates on the date and store.
CREATE VIEW dbo.v_f_sales_sumamt WITH SCHEMABINDING AS
(
SELECT date_key, store_key, sum(ISNULL(amt,0)) AS amt, count_big(*) AS cnt
FROM dbo.f_sales AS sales
GROUP BY date_key, store_key
)
GO

-- Materialize the view. The indexed view is now partition-aligned with table f_sales.
CREATE UNIQUE CLUSTERED INDEX ucidx_v_sales_sum
ON dbo.v_f_sales_sumamt (date_key) ON PS1(date_key)
GO

-- Check data distribution in various partitions of the table & the indexed view.
SELECT OBJECT_NAME(p.object_id) as obj_name, p.index_id, p.partition_number, p.rows, a.type, a.filegroup_id 
FROM sys.system_internals_allocation_units a
JOIN sys.partitions p
ON p.partition_id = a.container_id
WHERE p.object_id IN (OBJECT_ID(N'dbo.f_sales'), OBJECT_ID(N'dbo.v_f_sales_sumamt '))
ORDER BY obj_name, p.index_id, p.partition_number

-- Create archive table to receive the partition that will be switched out of table f_sales. 
CREATE TABLE dbo.sales_archive (date_key INT NOT NULL, cust_key INT, store_key INT, amt MONEY) ON FG1
GO
CREATE CLUSTERED INDEX UCIdx_sales_archive on dbo.sales_archive (date_key, cust_key, store_key) ON FG1
GO
--Create indexed view with view definition matching v_f_sales_sumamt on table f_sales.
CREATE VIEW dbo.v_sales_archive_sumamt WITH SCHEMABINDING AS
(
SELECT date_key, store_key, sum(ISNULL(amt,0)) AS amt, count_big(*) AS cnt
FROM dbo.sales_archive AS sales
GROUP BY date_key, store_key
)
GO

-- Materialize the view. The indexed view is partition-aligned with table sales_archive.
CREATE UNIQUE CLUSTERED INDEX ucidx_v_sales_sum
ON dbo.v_sales_archive_sumamt(date_key) ON FG1
GO

-- Check data distribution in various partitions of the table and the indexed view. 
SELECT OBJECT_NAME(p.object_id) as obj_name, p.index_id, p.partition_number, p.rows, a.type, a.filegroup_id 
FROM sys.system_internals_allocation_units a
JOIN sys.partitions p
ON p.partition_id = a.container_id
WHERE p.object_id IN (OBJECT_ID(N'dbo.sales_archive'), OBJECT_ID(N'dbo.v_sales_archive_sumamt '))
ORDER BY obj_name, p.index_id, p.partition_number

-- Data associated with the old partition of the source table - [f_sales] and the indexed view [v_f_sales_sumamt] - 
-- is switched out to archive table [sales_archive] and the indexed view [v_sales_archive_sumamt].
ALTER TABLE dbo.f_sales SWITCH PARTITION 1 TO dbo.sales_archive

-- Data distribution in various partitions shows that 
-- partition 1 of [f_sales] and the indexed view [v_f_sales_sumamt] are now empty 
-- and these rows are now in [sales_archive] and [v_sales_archive_sumamt], respectively.
SELECT OBJECT_NAME(p.object_id) as obj_name, p.index_id, p.partition_number, p.rows, a.type, a.filegroup_id 
FROM sys.system_internals_allocation_units a
JOIN sys.partitions p
ON p.partition_id = a.container_id
WHERE p.object_id IN (OBJECT_ID(N'dbo.sales_archive'), OBJECT_ID(N'dbo.v_sales_archive_sumamt '), 
OBJECT_ID(N'dbo.f_sales'), OBJECT_ID(N'dbo.v_f_sales_sumamt '))
ORDER BY obj_name, p.index_id, p.partition_number

如先前範例中所顯示，在進行資料分割切換後，所有在資料表 [f_sales] 的資料分割 1 以及索引檢視 [v_f_sales_sumamt] 中的資料，都已移動至對應的資料表 [sales_archive] 以及索引檢視 [v_sales_archive_sumamt] 中。

若要取得 2006 年 7 月依日期及依商店分類的銷售金額，您可以查詢資料表 [f_sales] 或索引檢視[v_f_sales_sumamt] (如下列兩個查詢所示)。兩個範例中的結果是相同的，但是執行索引檢視可大幅改進查詢效能，因為索引檢視會將預先計算的彙總具體化，並以 10 為因數減少資料列的數量，如下列範例所示。

-- This query runs against the table [f_sales]
SELECT date_key, store_key AS [Store Number], sum(ISNULL(amt,0)) AS Sales_Amount
FROM dbo.f_sales
WHERE date_key >= '20060701' AND date_key < '20060801'
GROUP BY date_key, store_key
ORDER BY date_key, store_key
OPTION (EXPAND VIEWS)

-- This query runs against the indexed view [v_f_sales_sumamt]
-- the result of this query is the same as the one against the table
-- the indexed view materializes the pre-calculated aggregate, resulting in significant improvements in query performance   
SELECT date_key, store_key AS [Store Number], sum(ISNULL(amt,0)) AS Sales_Amount
FROM dbo.v_f_sales_sumamt WITH (NOEXPAND)
WHERE date_key >= '20060701' AND date_key < '20060801'
GROUP BY date_key, store_key

使用 ALTER TABLE…SWITCH 陳述式進行資料分割切換，是一項迅速、僅處理中繼資料的作業。當以來源與目標資料表將索引檢視進行資料分割對齊時，資料分割切換可讓您將資料子集從來源資料表中帶入目標資料表，以及對齊的索引檢視的關聯部分。如此便能夠維持資料收集的完整性，因為所有與來源資料表相關聯的物件 (如資料表、索引，以及索引檢視) 都會包含在資料分割的切換當中。透過在資料分割資料表上使用索引檢視，您可以大幅增加參考該資料表的彙總查詢的效能。

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