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Table Variable Deferred Compilation

Table Variable Deferred Compilation (TVDC) improves plan quality and overall performance for queries that reference table variables. TVDC is a feature under the Intelligent Query Processing suite of features.

This example will show you how upgrading to Database Compatibility Level 150 could improve performance due to Table Variable Deferred Compilation, when your workload references table variables.

More information about this feature is available here.

Step 1: Setup WideWorldImportersDW database

You could choose to use a container to evaluate this feature. Create an instance of SQL Server 2019 using a Docker image and restore the WideWorldImportersDW database backup

You will need the WideWorldImportersDW database for this exercise. If you don't have this sample database, then you download the sample database here.

Restore the copied WideWorldImportersDW database backup into the container and restore the backup.

Docker Commands

docker pull mcr.microsoft.com/mssql/server:2019-latest

docker run -e "ACCEPT_EULA=Y" -e "SA_PASSWORD=`<A Strong Password`>" -p 1445:1433 --name sql2019demo -d mcr.microsoft.com/mssql/server:2019-latest

docker cp ".\Downloads\WideWorldImportersDW-Full.bak" sql2019demo:/var/opt/mssql/data

Note: For Linux installations the default path to use is /var/opt/mssql

In [7]:

USE [master]
GO
IF EXISTS (SELECT [database_id] FROM sys.databases WHERE [name] = 'WideWorldImportersDW')
ALTER DATABASE [WideWorldImportersDW] SET SINGLE_USER WITH ROLLBACK IMMEDIATE
GO

DECLARE @datafilepath VARCHAR(8000) = CAST(SERVERPROPERTY('InstanceDefaultDataPath') AS VARCHAR(4000)) + 'WideWorldImportersDW.mdf'
DECLARE @logfilepath VARCHAR(8000) = CAST(SERVERPROPERTY('InstanceDefaultLogPath') AS VARCHAR(4000)) + 'WideWorldImportersDW.ldf'
DECLARE @inmemfilepath VARCHAR(8000) = CAST(SERVERPROPERTY('InstanceDefaultDataPath') AS VARCHAR(4000)) + 'WideWorldImportersDW_InMemory_Data_1'
DECLARE @secondaryfilepath VARCHAR(8000) = CAST(SERVERPROPERTY('InstanceDefaultDataPath') AS VARCHAR(4000))+ 'WideWorldImportersDW_2.ndf'

-- Change @backupfile file path as needed
DECLARE @backupfile VARCHAR(8000) = 'E:\SampleDBs\WideWorldImportersDW-Full.bak'
RESTORE DATABASE WideWorldImportersDW
FROM DISK = @backupfile 
WITH MOVE 'WWI_Primary' TO @datafilepath,
    MOVE 'WWI_UserData' TO @secondaryfilepath,
    MOVE 'WWIDW_InMemory_Data_1' TO @inmemfilepath,
    MOVE 'WWI_Log' TO @logfilepath, NOUNLOAD, REPLACE, STATS = 10
GO

USE [master]
GO
ALTER DATABASE [WideWorldImportersDW] MODIFY FILE ( NAME = N'WWI_Log', SIZE = 4GB )
GO

Step 2: Enlarge the WideWorldImportersDW database

In [3]:

USE WideWorldImportersDW;
GO

/*
Assumes a fresh restore of WideWorldImportersDW
*/

IF OBJECT_ID('Fact.OrderHistory') IS NULL 
BEGIN
    SELECT [Order Key], [City Key], [Customer Key], [Stock Item Key], [Order Date Key], [Picked Date Key], [Salesperson Key], [Picker Key], [WWI Order ID], [WWI Backorder ID], Description, Package, Quantity, [Unit Price], [Tax Rate], [Total Excluding Tax], [Tax Amount], [Total Including Tax], [Lineage Key]
    INTO Fact.OrderHistory
    FROM Fact.[Order];
END;

ALTER TABLE Fact.OrderHistory
ADD CONSTRAINT PK_Fact_OrderHistory PRIMARY KEY NONCLUSTERED ([Order Key] ASC, [Order Date Key] ASC) WITH (DATA_COMPRESSION = PAGE);
GO

CREATE INDEX IX_Stock_Item_Key
ON Fact.OrderHistory ([Stock Item Key])
INCLUDE(Quantity)
WITH (DATA_COMPRESSION = PAGE);
GO

CREATE INDEX IX_OrderHistory_Quantity
ON Fact.OrderHistory ([Quantity])
INCLUDE([Order Key])
WITH (DATA_COMPRESSION = PAGE);
GO

CREATE INDEX IX_OrderHistory_CustomerKey
ON Fact.OrderHistory([Customer Key])
INCLUDE ([Total Including Tax])
WITH (DATA_COMPRESSION = PAGE);
GO

IF (SELECT COUNT(*) FROM [Fact].[OrderHistory]) < 3702592
BEGIN
	DECLARE @i smallint
	SET @i = 0
	WHILE @i < 4
	BEGIN
		INSERT INTO [Fact].[OrderHistory] ([City Key], [Customer Key], [Stock Item Key], [Order Date Key], [Picked Date Key], [Salesperson Key], [Picker Key], [WWI Order ID], [WWI Backorder ID], Description, Package, Quantity, [Unit Price], [Tax Rate], [Total Excluding Tax], [Tax Amount], [Total Including Tax], [Lineage Key])
		SELECT [City Key], [Customer Key], [Stock Item Key], [Order Date Key], [Picked Date Key], [Salesperson Key], [Picker Key], [WWI Order ID], [WWI Backorder ID], Description, Package, Quantity, [Unit Price], [Tax Rate], [Total Excluding Tax], [Tax Amount], [Total Including Tax], [Lineage Key]
		FROM [Fact].[OrderHistory];

		SET @i = @i +1
	END;
END
GO

IF OBJECT_ID('Fact.OrderHistoryExtended') IS NULL 
BEGIN
    SELECT [Order Key], [City Key], [Customer Key], [Stock Item Key], [Order Date Key], [Picked Date Key], [Salesperson Key], [Picker Key], [WWI Order ID], [WWI Backorder ID], Description, Package, Quantity, [Unit Price], [Tax Rate], [Total Excluding Tax], [Tax Amount], [Total Including Tax], [Lineage Key]
    INTO Fact.OrderHistoryExtended
    FROM Fact.[OrderHistory];
END;

ALTER TABLE Fact.OrderHistoryExtended
ADD CONSTRAINT PK_Fact_OrderHistoryExtended PRIMARY KEY NONCLUSTERED ([Order Key] ASC, [Order Date Key] ASC)
WITH (DATA_COMPRESSION = PAGE);
GO

CREATE INDEX IX_Stock_Item_Key
ON Fact.OrderHistoryExtended ([Stock Item Key])
INCLUDE (Quantity);
GO

IF (SELECT COUNT(*) FROM [Fact].[OrderHistory]) < 29620736
BEGIN
	DECLARE @i smallint
	SET @i = 0
	WHILE @i < 3
	BEGIN
		INSERT Fact.OrderHistoryExtended([City Key], [Customer Key], [Stock Item Key], [Order Date Key], [Picked Date Key], [Salesperson Key], [Picker Key], [WWI Order ID], [WWI Backorder ID], Description, Package, Quantity, [Unit Price], [Tax Rate], [Total Excluding Tax], [Tax Amount], [Total Including Tax], [Lineage Key])
		SELECT [City Key], [Customer Key], [Stock Item Key], [Order Date Key], [Picked Date Key], [Salesperson Key], [Picker Key], [WWI Order ID], [WWI Backorder ID], Description, Package, Quantity, [Unit Price], [Tax Rate], [Total Excluding Tax], [Tax Amount], [Total Including Tax], [Lineage Key]
		FROM Fact.OrderHistoryExtended;

		SET @i = @i +1
	END;
END
GO

UPDATE Fact.OrderHistoryExtended
SET [WWI Order ID] = [Order Key];
GO

-- Repeat the following until log shrinks. These demos don't require much log space.
CHECKPOINT
GO
DBCC SHRINKFILE (N'WWI_Log' , 0, TRUNCATEONLY)
GO
SELECT * FROM sys.dm_db_log_space_usage
GO

Step 3: Execute the query without Table Variable Deferred Compilation

If the database is configured with a non-default compatibility level scuh as 140 (which maps to SQL Server 2017), then TVDC is disabled.

In [1]:

USE [WideWorldImportersDW];
GO
ALTER DATABASE [WideWorldImportersDW] SET COMPATIBILITY_LEVEL = 140;
GO
ALTER DATABASE SCOPED CONFIGURATION CLEAR PROCEDURE_CACHE;
GO

DECLARE @Order TABLE 
	([Order Key] BIGINT NOT NULL,
	 [Quantity] INT NOT NULL
	);

INSERT @Order
SELECT [Order Key], [Quantity]
FROM [Fact].[OrderHistory]
WHERE  [Quantity] > 99;

SELECT oh.[Order Key], oh.[Order Date Key],
	   oh.[Unit Price], o.Quantity
FROM Fact.OrderHistoryExtended AS oh
INNER JOIN @Order AS o
	ON o.[Order Key] = oh.[Order Key]
WHERE oh.[Unit Price] > 0.10
ORDER BY oh.[Unit Price] DESC;
GO

Out [1]:

Commands completed successfully.

(490928 rows affected)

Displaying Top 500 rows.

Total execution time: 00:00:17.819

Order Key	Order Date Key	Unit Price	Quantity
797013	2015-10-14	112.00	100
593327	2014-02-28	112.00	100
804535	2014-12-05	112.00	100
907476	2013-03-11	112.00	100
826912	2014-05-19	112.00	100
834650	2015-11-16	112.00	100
666744	2013-12-09	112.00	100
646938	2013-09-12	112.00	100
894950	2015-07-18	112.00	100
847187	2015-01-13	112.00	100
997865	2013-07-25	112.00	100
997875	2013-09-19	112.00	100
997882	2013-10-10	112.00	100
997972	2015-07-16	112.00	100
967326	2015-07-18	112.00	100
1195710	2014-01-24	112.00	100
977452	2013-04-19	112.00	100
977454	2013-04-19	112.00	100
977467	2013-05-02	112.00	100
977470	2013-05-08	112.00	100
977620	2013-06-14	112.00	100
1396345	2015-07-18	112.00	100
1398855	2015-12-09	112.00	100
1020660	2015-12-18	112.00	100
1576788	2014-07-04	112.00	100
1140180	2015-01-26	112.00	100
1476688	2015-03-10	112.00	100
1336420	2015-03-03	112.00	100
1339003	2015-08-12	112.00	100
1536395	2015-04-22	112.00	100
1536686	2015-05-21	112.00	100
1204298	2014-11-10	112.00	100
1446337	2014-01-29	112.00	100
1486575	2014-02-14	112.00	100
1486722	2015-01-14	112.00	100
1326484	2015-03-16	112.00	100
1846919	2014-04-24	112.00	100
1910787	2015-08-20	112.00	100
2376042	2015-03-16	112.00	100
2042282	2015-09-23	112.00	100
2131543	2014-03-05	112.00	100
1687346	2015-07-29	112.00	100
2181115	2014-03-12	112.00	100
2109470	2015-08-26	112.00	100
2423537	2014-11-10	112.00	100
2426127	2015-12-15	112.00	100
2524449	2013-03-11	112.00	100
2343435	2014-09-25	112.00	100
2303411	2013-04-12	112.00	100
2303418	2013-04-18	112.00	100
2383507	2014-03-05	112.00	100
2883067	2014-09-25	112.00	100
2637457	2015-08-26	112.00	100
2645282	2014-12-05	112.00	100
2647675	2013-11-11	112.00	100
2617201	2015-05-21	112.00	100
2695895	2013-07-20	112.00	100
2913090	2016-05-02	112.00	100
2915427	2013-03-11	112.00	100
2685543	2013-03-11	112.00	100
2733560	2013-09-12	112.00	100
3258043	2014-02-14	112.00	100
3219065	2014-03-12	112.00	100
3221612	2015-12-09	112.00	100
2765666	2015-04-15	112.00	100
2966472	2015-07-10	112.00	100
2948135	2015-10-20	112.00	100
3032792	2014-07-04	112.00	100
3104547	2014-03-05	112.00	100
3113511	2015-09-23	112.00	100
3385795	2015-12-18	112.00	100
3425505	2015-02-25	112.00	100
3427939	2013-03-19	112.00	100
3290854	2014-12-17	112.00	100
3643819	2014-11-10	112.00	100
158006	2015-05-29	112.00	100
40963	2013-08-28	112.00	100
40193	2013-08-23	112.00	100
43448	2013-09-12	112.00	100
182011	2015-09-23	112.00	100
276176	2015-11-14	112.00	100
276254	2015-01-13	112.00	100
276258	2015-01-14	112.00	100
1065768	2014-12-10	112.00	100
1332309	2015-04-17	112.00	100
1339219	2016-02-10	112.00	100
1322349	2016-05-02	112.00	100
1322676	2015-06-06	112.00	100
1219828	2015-01-26	112.00	100
1519419	2016-02-11	112.00	100
1640051	2015-05-21	112.00	100
2075497	2015-12-15	112.00	100
1482324	2015-11-14	112.00	100
1898852	2014-10-06	112.00	100
1462489	2013-11-20	112.00	100
1569315	2015-07-10	112.00	100
1703441	2015-11-27	112.00	100
1225553	2014-02-18	112.00	100
1743241	2015-07-16	112.00	100
1964371	2014-02-28	112.00	100
2416212	2015-03-19	112.00	100
2194592	2014-10-06	112.00	100
3632623	2013-07-23	112.00	100
350404	2014-12-17	112.00	100
289738	2013-05-02	112.00	100
289741	2013-05-08	112.00	100
320315	2014-12-05	112.00	100
402037	2015-01-26	112.00	100
441819	2015-09-08	112.00	100
371119	2013-11-11	112.00	100
371236	2015-09-26	112.00	100
441966	2015-10-14	112.00	100
392108	2015-11-03	112.00	100
371407	2013-11-20	112.00	100
498799	2014-09-25	112.00	100
505917	2014-10-06	112.00	100
606096	2015-12-09	112.00	100
529434	2014-08-02	112.00	100
586197	2015-04-17	112.00	100
609494	2016-02-20	112.00	100
1834535	2015-03-20	112.00	100
1896830	2016-02-10	112.00	100
2060033	2014-01-24	112.00	100
1824468	2015-08-10	112.00	100
2232875	2013-07-25	112.00	100
1885573	2015-05-26	112.00	100
2299049	2015-04-22	112.00	100
1923139	2015-09-26	112.00	100
1923259	2015-10-06	112.00	100
1923265	2015-10-09	112.00	100
2496748	2013-11-20	112.00	100
2499834	2015-08-15	112.00	100
2499902	2015-01-26	112.00	100
2121790	2015-03-10	112.00	100
2536949	2014-04-24	112.00	100
2181191	2014-08-02	112.00	100
2183489	2014-04-24	112.00	100
2319235	2014-03-24	112.00	100
2915717	2013-06-14	112.00	100
2736430	2013-12-23	112.00	100
2469529	2013-02-11	112.00	100
2658065	2015-08-26	112.00	100
2570267	2014-06-19	112.00	100
2779334	2015-11-11	112.00	100
2590121	2014-12-10	112.00	100
2846340	2015-11-11	112.00	100
2788944	2013-08-23	112.00	100
2789003	2015-08-12	112.00	100
3062085	2013-09-19	112.00	100
2935571	2016-01-04	112.00	100
3421373	2015-05-29	112.00	100
3224735	2015-09-05	112.00	100
3284235	2015-08-10	112.00	100
2866033	2015-10-06	112.00	100
3012213	2016-02-11	112.00	100
3441136	2014-06-19	112.00	100
2971092	2014-08-02	112.00	100
3046121	2013-06-03	112.00	100
2711887	2015-01-13	112.00	100
3028193	2016-01-04	112.00	100
3031218	2013-07-23	112.00	100
3107060	2015-10-14	112.00	100
3559784	2014-04-24	112.00	100
3273967	2016-01-04	112.00	100
3351180	2013-04-18	112.00	100
3493758	2015-08-22	112.00	100
3175116	2014-05-19	112.00	100
3624193	2013-06-03	112.00	100
3632406	2013-06-14	112.00	100
3549730	2013-06-26	112.00	100
820116	2014-08-18	112.00	100
730549	2015-12-18	112.00	100
730790	2015-11-03	112.00	100
867649	2016-02-10	112.00	100
720483	2013-11-11	112.00	100
720618	2013-11-20	112.00	100
800330	2014-01-24	112.00	100
928751	2016-05-02	112.00	100
797100	2013-07-20	112.00	100
827297	2013-04-19	112.00	100
827299	2013-04-19	112.00	100
837225	2015-04-22	112.00	100
830338	2014-07-04	112.00	100
993688	2015-03-03	112.00	100
1094714	2014-01-29	112.00	100
1359014	2014-07-07	112.00	100
1000561	2014-01-06	112.00	100
1459069	2014-03-05	112.00	100
1120618	2015-11-16	112.00	100
1151157	2015-05-26	112.00	100
1572398	2015-11-16	112.00	100
53082	2013-11-11	112.00	100
54877	2013-11-20	112.00	100
58034	2013-12-09	112.00	100
202005	2016-01-04	112.00	100
202038	2016-01-04	112.00	100
9549	2013-03-04	112.00	100
17717	2013-04-19	112.00	100
19893	2013-05-02	112.00	100
17861	2013-04-19	112.00	100
21244	2013-05-08	112.00	100
27904	2013-06-14	112.00	100
35147	2013-07-23	112.00	100
149422	2015-04-17	112.00	100
126886	2014-12-24	112.00	100
316882	2014-01-24	112.00	100
286389	2013-04-16	112.00	100
365129	2013-08-23	112.00	100
365142	2013-08-28	112.00	100
304100	2016-03-01	112.00	100
283874	2015-08-26	112.00	100
436405	2013-12-23	112.00	100
406590	2015-03-16	112.00	100
865076	2014-12-17	112.00	100
513161	2015-03-19	112.00	100
3642951	2014-02-14	112.00	100
3135856	2013-09-19	112.00	100
3334080	2015-04-22	112.00	100
3635466	2014-04-26	112.00	100
384942	2015-03-19	112.00	100
622536	2015-03-20	112.00	100
863628	2014-01-24	112.00	100
522194	2015-03-03	112.00	100
522485	2015-03-20	112.00	100
552959	2014-04-24	112.00	100
582517	2013-07-25	112.00	100
903945	2013-03-19	112.00	100
923819	2015-09-05	112.00	100
914059	2015-08-28	112.00	100
996496	2015-11-27	112.00	100
1114847	2015-12-09	112.00	100
883578	2015-07-16	112.00	100
1006552	2016-05-26	112.00	100
1512304	2013-11-11	112.00	100
1515312	2014-04-24	112.00	100
1492418	2015-12-09	112.00	100
1636107	2015-08-28	112.00	100
966217	2015-01-13	112.00	100
1395241	2015-11-03	112.00	100
1023870	2015-02-25	112.00	100
1575565	2015-03-07	112.00	100
1147263	2013-08-28	112.00	100
1147250	2013-08-23	112.00	100
1615958	2014-04-11	112.00	100
1221294	2015-08-20	112.00	100
1221305	2015-08-22	112.00	100
1221405	2014-02-14	112.00	100
1221462	2014-03-05	112.00	100
1325388	2016-02-20	112.00	100
1505639	2013-02-11	112.00	100
1545315	2015-08-12	112.00	100
1482196	2015-11-27	112.00	100
1585670	2014-02-26	112.00	100
1465436	2015-08-28	112.00	100
2035780	2015-09-08	112.00	100
1693006	2014-08-18	112.00	100
1696377	2014-04-22	112.00	100
1746335	2014-06-19	112.00	100
1746358	2015-03-07	112.00	100
1823137	2015-09-23	112.00	100
1756540	2015-08-20	112.00	100
2482694	2015-11-14	112.00	100
2583126	2015-03-16	112.00	100
2583308	2014-11-13	112.00	100
2742339	2014-01-24	112.00	100
2742381	2015-10-20	112.00	100
2742246	2014-01-06	112.00	100
2472501	2015-03-16	112.00	100
2965914	2014-12-24	112.00	100
2844236	2013-06-26	112.00	100
2928434	2014-08-20	112.00	100
2984951	2013-03-04	112.00	100
3257010	2013-06-20	112.00	100
2772261	2013-07-23	112.00	100
3283921	2013-07-25	112.00	100
3283931	2013-09-19	112.00	100
3283938	2013-10-10	112.00	100
2633861	2014-01-24	112.00	100
2891754	2014-07-04	112.00	100
2654265	2015-07-16	112.00	100
3460936	2014-04-11	112.00	100
3461043	2013-03-19	112.00	100
3461133	2014-08-18	112.00	100
3051723	2015-03-16	112.00	100
3073641	2014-03-24	112.00	100
3542939	2014-03-12	112.00	100
3324020	2016-03-01	112.00	100
3112218	2015-08-15	112.00	100
3112230	2015-08-27	112.00	100
3404515	2015-10-09	112.00	100
3404449	2015-10-06	112.00	100
3562718	2014-12-17	112.00	100
3357068	2014-04-22	112.00	100
2733433	2015-04-17	112.00	100
3224323	2013-06-26	112.00	100
2768790	2015-10-06	112.00	100
2768796	2015-10-09	112.00	100
2768828	2016-05-11	112.00	100
3283823	2014-04-11	112.00	100
3303776	2014-12-05	112.00	100
2947887	2014-11-10	112.00	100
3146716	2013-03-04	112.00	100
3125337	2015-08-10	112.00	100
3241106	2014-02-18	112.00	100
3250173	2015-08-15	112.00	100
2853380	2015-05-21	112.00	100
3330729	2015-05-21	112.00	100
3101547	2015-09-26	112.00	100
3104038	2015-06-06	112.00	100
3106527	2014-12-17	112.00	100
3106609	2015-09-08	112.00	100
3132497	2014-12-10	112.00	100
428443	2015-03-10	112.00	100
441397	2015-08-12	112.00	100
809705	2016-01-04	112.00	100
598846	2013-06-20	112.00	100
854395	2015-05-29	112.00	100
618964	2013-06-03	112.00	100
498395	2013-06-20	112.00	100
870170	2015-12-15	112.00	100
750856	2014-01-06	112.00	100
876988	2016-03-01	112.00	100
508619	2013-06-14	112.00	100
508805	2013-07-23	112.00	100
515677	2016-03-01	112.00	100
719927	2013-04-18	112.00	100
525809	2014-04-22	112.00	100
720131	2013-06-26	112.00	100
720203	2015-04-22	112.00	100
796766	2015-09-08	112.00	100
583341	2014-05-19	112.00	100
576042	2014-10-06	112.00	100
836955	2015-05-21	112.00	100
959706	2014-07-07	112.00	100
846900	2015-11-14	112.00	100
1135362	2014-09-25	112.00	100
1135504	2013-06-03	112.00	100
1632767	2016-03-01	112.00	100
967011	2015-01-14	112.00	100
969380	2015-04-22	112.00	100
1090656	2013-06-26	112.00	100
1090789	2013-11-11	112.00	100
1091070	2013-11-20	112.00	100
979761	2015-12-09	112.00	100
979801	2014-07-04	112.00	100
977175	2013-03-04	112.00	100
982981	2016-02-20	112.00	100
1391549	2015-12-18	112.00	100
1111440	2014-04-26	112.00	100
1000004	2015-09-05	112.00	100
1125266	2014-03-24	112.00	100
1150679	2013-09-12	112.00	100
1579002	2013-07-23	112.00	100
1471976	2015-10-20	112.00	100
1616912	2013-03-11	112.00	100
1558624	2015-08-28	112.00	100
1556230	2015-09-23	112.00	100
1558847	2014-03-05	112.00	100
1043431	2014-02-28	112.00	100
1236127	2014-11-10	112.00	100
1277862	2013-12-23	112.00	100
1293267	2014-11-13	112.00	100
1219472	2014-11-13	112.00	100
1498906	2014-09-12	112.00	100
1502239	2015-11-11	112.00	100
1521924	2015-08-26	112.00	100
2075149	2014-02-14	112.00	100
1797589	2015-08-28	112.00	100
1361639	2013-07-20	112.00	100
1408577	2015-09-26	112.00	100
1428302	2015-02-02	112.00	100
1834244	2015-03-03	112.00	100
1836621	2015-05-26	112.00	100
1912880	2015-04-17	112.00	100
1916075	2015-08-10	112.00	100
1916196	2016-05-26	112.00	100
1486316	2016-01-04	112.00	100
1922462	2015-08-15	112.00	100
1922474	2015-08-27	112.00	100
1602551	2013-02-11	112.00	100
2059606	2016-02-20	112.00	100
2012606	2015-04-17	112.00	100
1719365	2014-12-24	112.00	100
1737031	2014-02-26	112.00	100
1861562	2015-11-16	112.00	100
1306216	2014-11-10	112.00	100
1346266	2015-09-08	112.00	100
1963940	2014-02-14	112.00	100
2413224	2013-07-23	112.00	100
2435805	2016-02-20	112.00	100
1784868	2013-04-16	112.00	100
2235046	2015-03-03	112.00	100
1850017	2014-12-24	112.00	100
2258668	2015-10-14	112.00	100
2402259	2015-03-10	112.00	100
1927582	2014-11-13	112.00	100
2127975	2014-03-12	112.00	100
2128027	2014-02-18	112.00	100
2462406	2014-01-29	112.00	100
2281706	2013-09-19	112.00	100
2281713	2013-10-10	112.00	100
2281850	2013-09-19	112.00	100
2322180	2015-07-10	112.00	100
2362122	2014-02-14	112.00	100
2452636	2013-07-20	112.00	100
2251809	2014-11-10	112.00	100
2372170	2015-04-15	112.00	100
3464704	2015-10-20	112.00	100
3405254	2013-11-06	112.00	100
3407931	2015-07-16	112.00	100
3388111	2013-07-25	112.00	100
3583279	2015-05-29	112.00	100
3585775	2013-07-25	112.00	100
3565841	2014-02-26	112.00	100
3566104	2015-07-16	112.00	100
3353670	2013-11-11	112.00	100
3476106	2015-03-19	112.00	100
3529533	2016-01-04	112.00	100
3533964	2015-03-16	112.00	100
3516487	2015-07-10	112.00	100
3643606	2016-05-26	112.00	100
3620634	2013-11-06	112.00	100
3595935	2015-03-07	112.00	100
3617124	2015-05-26	112.00	100
3617188	2013-06-20	112.00	100
3678203	2015-03-07	112.00	100
192658	2015-11-16	112.00	100
65885	2014-01-24	112.00	100
86430	2014-05-19	112.00	100
2902230	2015-12-18	112.00	100
2828988	2014-12-05	112.00	100
3201268	2015-01-26	112.00	100
3247446	2015-08-27	112.00	100
3375341	2015-03-03	112.00	100
3643413	2014-02-28	112.00	100
3659525	2015-12-15	112.00	100
227209	2016-05-11	112.00	100
225026	2016-05-02	112.00	100
16508	2013-04-12	112.00	100
17590	2013-04-18	112.00	100
29978	2013-06-26	112.00	100
157080	2015-05-26	112.00	100
52501	2013-11-06	112.00	100
130779	2015-01-14	112.00	100
130562	2015-01-13	112.00	100
150421	2015-04-22	112.00	100
209060	2016-02-10	112.00	100
212798	2016-03-01	112.00	100
6721	2013-02-11	112.00	100
198344	2015-12-15	112.00	100
62536	2014-01-06	112.00	100
296074	2014-09-12	112.00	100
336328	2014-12-24	112.00	100
286083	2014-04-22	112.00	100
283359	2015-08-10	112.00	100
289469	2014-07-04	112.00	100
370694	2015-08-15	112.00	100
370706	2015-08-27	112.00	100
1616756	2013-03-04	112.00	100
1596582	2015-03-16	112.00	100
1486184	2013-06-14	112.00	100
1566088	2013-03-04	112.00	100
1566130	2013-08-28	112.00	100
1566117	2013-08-23	112.00	100
1810553	2013-06-26	112.00	100
2252647	2015-12-09	112.00	100
2335420	2015-11-03	112.00	100
2295312	2013-04-12	112.00	100
2298675	2013-06-26	112.00	100
2378984	2015-08-12	112.00	100
2042086	2013-07-20	112.00	100
2594248	2015-08-28	112.00	100
2459230	2015-03-03	112.00	100
1689320	2015-09-23	112.00	100
2533919	2015-10-06	112.00	100
2533925	2015-10-09	112.00	100
2534009	2014-04-26	112.00	100
2534090	2014-01-06	112.00	100
2536706	2015-12-09	112.00	100
2104560	2015-08-10	112.00	100
1830159	2015-03-16	112.00	100
2225013	2016-05-02	112.00	100
1869380	2016-05-02	112.00	100
2358874	2015-09-05	112.00	100
2425754	2016-01-04	112.00	100
2918618	2013-07-23	112.00	100
2526266	2015-09-26	112.00	100
2977445	2015-02-02	112.00	100
2677526	2015-08-28	112.00	100
2403283	2015-10-14	112.00	100
2824246	2015-01-26	112.00	100
2302981	2015-09-23	112.00	100
2305571	2013-09-12	112.00	100
2469198	2014-01-06	112.00	100
2634707	2015-07-18	112.00	100
2170698	2014-04-24	112.00	100
2616951	2014-01-29	112.00	100
2620087	2014-09-25	112.00	100
2620220	2013-09-12	112.00	100
2620173	2015-02-02	112.00	100

Observe the query execution plan (or actual plan).

Notice the actual vs. estimated rows for the @Order Table Scan. Only one row estimated vs. 490k rows actual rows, which represents a sizeable misestimation.

Note: Table Variables only exist at runtime, which means that SQL Server cannot properly estimate the number of rows for these objects. And so, the legacy behavior for lower compatibility levels is to estimate only one row for Table Variables.

In turn, this misestimation propagates up the plan, namely impacting the join algorithm chosen (Nested Loops) which are more efficient for smaller input tables.

Step 4: Execute the query by removing any hint restriction

Run the same query from Step 3, but now with the default compatibility level (150), allowing SQL Server to use Table Variable Deferred Compilation.

In [2]:

USE [WideWorldImportersDW];
GO
ALTER DATABASE [WideWorldImportersDW] SET COMPATIBILITY_LEVEL = 150;
GO
ALTER DATABASE SCOPED CONFIGURATION CLEAR PROCEDURE_CACHE;
GO

DECLARE @Order TABLE 
	([Order Key] BIGINT NOT NULL,
	 [Quantity] INT NOT NULL
	);

INSERT @Order
SELECT [Order Key], [Quantity]
FROM [Fact].[OrderHistory]
WHERE  [Quantity] > 99;

SELECT oh.[Order Key], oh.[Order Date Key],
	   oh.[Unit Price], o.Quantity
FROM Fact.OrderHistoryExtended AS oh
INNER JOIN @Order AS o
	ON o.[Order Key] = oh.[Order Key]
WHERE oh.[Unit Price] > 0.10
ORDER BY oh.[Unit Price] DESC;
GO

Out [2]:

Commands completed successfully.

(490928 rows affected)

Displaying Top 500 rows.

Total execution time: 00:00:08.024

Order Key	Order Date Key	Unit Price	Quantity
803965	2015-09-23	112.00	100
3566104	2015-07-16	112.00	100
1579002	2013-07-23	112.00	100
999261	2014-08-18	112.00	100
3264278	2014-02-28	112.00	100
1521924	2015-08-26	112.00	100
140937	2015-03-07	112.00	100
2837173	2015-02-02	112.00	100
170918	2015-07-29	112.00	100
2745292	2015-12-18	112.00	100
831218	2013-04-16	112.00	100
883578	2015-07-16	112.00	100
1337665	2014-05-19	112.00	100
297273	2015-12-09	112.00	100
72938	2014-03-05	112.00	100
2505330	2014-03-05	112.00	100
1536395	2015-04-22	112.00	100
1447349	2014-08-18	112.00	100
1447302	2014-04-11	112.00	100
999236	2014-04-24	112.00	100
371236	2015-09-26	112.00	100
3197723	2014-04-26	112.00	100
1094839	2014-08-20	112.00	100
27904	2013-06-14	112.00	100
1905314	2015-03-20	112.00	100
855574	2015-08-28	112.00	100
1830159	2015-03-16	112.00	100
2506456	2015-07-16	112.00	100
2519161	2013-12-23	112.00	100
2302981	2015-09-23	112.00	100
3436772	2014-01-29	112.00	100
1869380	2016-05-02	112.00	100
2303411	2013-04-12	112.00	100
1095046	2014-04-22	112.00	100
1062677	2014-12-05	112.00	100
1447061	2014-04-26	112.00	100
1687346	2015-07-29	112.00	100
2465190	2015-07-29	112.00	100
2076857	2014-03-24	112.00	100
417481	2013-04-12	112.00	100
3677324	2013-06-14	112.00	100
3262458	2015-11-14	112.00	100
2306577	2013-03-19	112.00	100
2305044	2013-11-20	112.00	100
1827776	2014-03-12	112.00	100
3108935	2015-12-15	112.00	100
2305571	2013-09-12	112.00	100
1558847	2014-03-05	112.00	100
3642951	2014-02-14	112.00	100
1444143	2013-12-23	112.00	100
1522946	2013-04-12	112.00	100
641937	2013-08-23	112.00	100
2302711	2013-11-11	112.00	100
1621774	2016-02-20	112.00	100
720131	2013-06-26	112.00	100
3436966	2013-11-20	112.00	100
2042282	2015-09-23	112.00	100
1000561	2014-01-06	112.00	100
2809785	2014-12-17	112.00	100
2075497	2015-12-15	112.00	100
1444700	2015-08-15	112.00	100
1444712	2015-08-27	112.00	100
2328401	2014-03-24	112.00	100
719927	2013-04-18	112.00	100
2246451	2015-03-10	112.00	100
3108749	2014-12-17	112.00	100
396852	2015-04-15	112.00	100
2303418	2013-04-18	112.00	100
2075149	2014-02-14	112.00	100
641950	2013-08-28	112.00	100
720203	2015-04-22	112.00	100
1558624	2015-08-28	112.00	100
1904838	2015-03-03	112.00	100
284549	2013-09-19	112.00	100
3456822	2013-04-19	112.00	100
1000004	2015-09-05	112.00	100
284556	2013-10-10	112.00	100
3077604	2015-09-23	112.00	100
3073197	2015-03-16	112.00	100
1032238	2013-12-23	112.00	100
3402166	2015-03-16	112.00	100
75884	2014-03-24	112.00	100
826912	2014-05-19	112.00	100
149079	2015-04-15	112.00	100
371119	2013-11-11	112.00	100
3678203	2015-03-07	112.00	100
1632767	2016-03-01	112.00	100
720483	2013-11-11	112.00	100
11024	2013-03-11	112.00	100
1579661	2013-05-08	112.00	100
2984951	2013-03-04	112.00	100
1338336	2015-11-11	112.00	100
1446337	2014-01-29	112.00	100
1519419	2016-02-11	112.00	100
3562718	2014-12-17	112.00	100
3105501	2015-03-07	112.00	100
1579658	2013-05-02	112.00	100
3456084	2014-08-20	112.00	100
1829208	2015-02-02	112.00	100
3643819	2014-11-10	112.00	100
3200506	2013-03-11	112.00	100
261698	2013-06-20	112.00	100
3107060	2015-10-14	112.00	100
266461	2015-04-17	112.00	100
3643606	2016-05-26	112.00	100
525809	2014-04-22	112.00	100
1031174	2015-03-19	112.00	100
198344	2015-12-15	112.00	100
2520996	2014-04-11	112.00	100
1810553	2013-06-26	112.00	100
320315	2014-12-05	112.00	100
1359014	2014-07-07	112.00	100
3695241	2015-03-16	112.00	100
2633861	2014-01-24	112.00	100
3106609	2015-09-08	112.00	100
3106527	2014-12-17	112.00	100
287450	2016-01-04	112.00	100
3106258	2013-12-23	112.00	100
2042086	2013-07-20	112.00	100
732215	2015-02-25	112.00	100
1535931	2013-06-26	112.00	100
1536686	2015-05-21	112.00	100
3073641	2014-03-24	112.00	100
3489492	2014-11-13	112.00	100
3197383	2015-07-18	112.00	100
2241935	2014-05-19	112.00	100
1689320	2015-09-23	112.00	100
732449	2015-07-10	112.00	100
3079353	2015-09-23	112.00	100
3011353	2014-03-12	112.00	100
1363256	2015-10-14	112.00	100
3105964	2015-08-12	112.00	100
1903779	2015-04-15	112.00	100
35147	2013-07-23	112.00	100
2633486	2015-11-14	112.00	100
3643413	2014-02-28	112.00	100
2543457	2014-07-07	112.00	100
3620634	2013-11-06	112.00	100
752933	2015-09-05	112.00	100
2503838	2015-03-20	112.00	100
2304415	2015-12-09	112.00	100
3463676	2015-10-20	112.00	100
2982816	2014-02-26	112.00	100
3188140	2015-12-18	112.00	100
3012213	2016-02-11	112.00	100
834650	2015-11-16	112.00	100
3565841	2014-02-26	112.00	100
1622471	2016-05-02	112.00	100
1631335	2014-04-22	112.00	100
1446738	2014-08-20	112.00	100
417488	2013-04-18	112.00	100
3463718	2015-08-27	112.00	100
3456820	2013-04-19	112.00	100
854395	2015-05-29	112.00	100
25555	2013-06-03	112.00	100
395659	2013-11-06	112.00	100
3224735	2015-09-05	112.00	100
2961404	2015-02-25	112.00	100
390542	2013-06-03	112.00	100
1784416	2016-01-04	112.00	100
2012606	2015-04-17	112.00	100
1476688	2015-03-10	112.00	100
1456768	2013-11-11	112.00	100
1545315	2015-08-12	112.00	100
2966472	2015-07-10	112.00	100
2205484	2014-04-26	112.00	100
863628	2014-01-24	112.00	100
9549	2013-03-04	112.00	100
3201268	2015-01-26	112.00	100
575666	2015-08-10	112.00	100
1624680	2014-05-19	112.00	100
1592244	2015-09-05	112.00	100
1311683	2014-03-05	112.00	100
411014	2015-07-16	112.00	100
1457622	2013-03-19	112.00	100
2864698	2013-03-04	112.00	100
1477024	2015-11-14	112.00	100
1545714	2015-10-20	112.00	100
1483188	2015-10-14	112.00	100
17861	2013-04-19	112.00	100
2376042	2015-03-16	112.00	100
17717	2013-04-19	112.00	100
19893	2013-05-02	112.00	100
1477058	2015-05-26	112.00	100
2393870	2016-05-02	112.00	100
2533925	2015-10-09	112.00	100
21244	2013-05-08	112.00	100
2533919	2015-10-06	112.00	100
1326484	2015-03-16	112.00	100
3699294	2015-08-12	112.00	100
2205230	2015-08-12	112.00	100
3474170	2015-07-29	112.00	100
2013592	2015-05-21	112.00	100
1453498	2015-12-15	112.00	100
1262309	2013-08-28	112.00	100
2915427	2013-03-11	112.00	100
1308198	2013-11-06	112.00	100
3380953	2015-08-28	112.00	100
1453636	2015-06-06	112.00	100
283359	2015-08-10	112.00	100
3659525	2015-12-15	112.00	100
2534090	2014-01-06	112.00	100
2406943	2016-05-26	112.00	100
1482324	2015-11-14	112.00	100
1163857	2015-03-19	112.00	100
2590121	2014-12-10	112.00	100
474192	2016-05-11	112.00	100
1482866	2013-07-20	112.00	100
2127975	2014-03-12	112.00	100
2128027	2014-02-18	112.00	100
3405254	2013-11-06	112.00	100
1545059	2016-01-04	112.00	100
2534009	2014-04-26	112.00	100
1876656	2013-07-20	112.00	100
2279107	2015-04-17	112.00	100
1219472	2014-11-13	112.00	100
3224323	2013-06-26	112.00	100
1786700	2015-07-16	112.00	100
3004245	2014-01-24	112.00	100
836955	2015-05-21	112.00	100
3222172	2016-02-11	112.00	100
1569315	2015-07-10	112.00	100
3404515	2015-10-09	112.00	100
3221612	2015-12-09	112.00	100
3542939	2014-03-12	112.00	100
3404449	2015-10-06	112.00	100
369874	2015-07-18	112.00	100
1177368	2014-06-19	112.00	100
1812835	2015-08-27	112.00	100
1812794	2015-08-15	112.00	100
3273967	2016-01-04	112.00	100
1133349	2015-09-23	112.00	100
311730	2014-08-20	112.00	100
311692	2014-01-29	112.00	100
1784868	2013-04-16	112.00	100
1417477	2014-06-19	112.00	100
1512304	2013-11-11	112.00	100
3583279	2015-05-29	112.00	100
2724876	2013-08-23	112.00	100
2185225	2013-04-19	112.00	100
2897795	2015-08-22	112.00	100
2724889	2013-08-28	112.00	100
2185227	2013-04-19	112.00	100
742255	2014-02-26	112.00	100
2897784	2015-08-20	112.00	100
1513499	2013-06-20	112.00	100
2281850	2013-09-19	112.00	100
859098	2015-12-09	112.00	100
3554403	2015-12-15	112.00	100
661186	2016-02-11	112.00	100
2896790	2016-02-20	112.00	100
2281713	2013-10-10	112.00	100
3545695	2015-12-15	112.00	100
3115977	2015-10-06	112.00	100
759333	2013-04-16	112.00	100
3085889	2013-11-20	112.00	100
3181227	2014-04-22	112.00	100
2183489	2014-04-24	112.00	100
894950	2015-07-18	112.00	100
2281706	2013-09-19	112.00	100
2403283	2015-10-14	112.00	100
1134468	2015-08-28	112.00	100
3204140	2014-08-02	112.00	100
493967	2013-08-23	112.00	100
3116257	2015-10-09	112.00	100
1220430	2015-11-27	112.00	100
2131543	2014-03-05	112.00	100
2013298	2014-03-05	112.00	100
866195	2014-03-12	112.00	100
1530047	2013-04-18	112.00	100
493980	2013-08-28	112.00	100
899467	2013-02-11	112.00	100
3474984	2014-12-10	112.00	100
3475403	2015-09-08	112.00	100
2404790	2013-07-20	112.00	100
823805	2014-04-11	112.00	100
2373876	2014-04-26	112.00	100
1219828	2015-01-26	112.00	100
66682	2014-01-29	112.00	100
2591255	2015-05-29	112.00	100
195095	2015-11-27	112.00	100
2565599	2015-05-26	112.00	100
1484351	2015-08-22	112.00	100
1134065	2015-04-15	112.00	100
3272039	2015-08-15	112.00	100
1668138	2015-07-10	112.00	100
3555471	2015-06-06	112.00	100
3272408	2015-11-27	112.00	100
1484340	2015-08-20	112.00	100
2281543	2013-07-25	112.00	100
3476106	2015-03-19	112.00	100
865076	2014-12-17	112.00	100
2184769	2013-03-04	112.00	100
1953770	2014-08-18	112.00	100
1394159	2015-01-14	112.00	100
2130909	2014-04-22	112.00	100
3553054	2013-11-11	112.00	100
1395241	2015-11-03	112.00	100
3272202	2015-08-27	112.00	100
3553063	2013-11-20	112.00	100
1454462	2015-11-16	112.00	100
3481526	2013-03-04	112.00	100
2565965	2015-11-03	112.00	100
3585775	2013-07-25	112.00	100
428443	2015-03-10	112.00	100
344691	2014-03-12	112.00	100
513161	2015-03-19	112.00	100
2549512	2014-08-02	112.00	100
3105017	2015-04-15	112.00	100
1486184	2013-06-14	112.00	100
1917182	2015-08-26	112.00	100
308713	2014-08-18	112.00	100
288476	2014-08-02	112.00	100
2523546	2014-07-04	112.00	100
1331634	2015-12-09	112.00	100
3104547	2014-03-05	112.00	100
380505	2015-04-22	112.00	100
2552206	2015-09-05	112.00	100
512547	2016-02-20	112.00	100
3641890	2015-01-26	112.00	100
2472501	2015-03-16	112.00	100
1916742	2015-01-26	112.00	100
2472138	2016-05-26	112.00	100
1916196	2016-05-26	112.00	100
2249717	2015-04-17	112.00	100
796165	2015-08-12	112.00	100
2311675	2014-12-05	112.00	100
2496748	2013-11-20	112.00	100
380271	2015-11-16	112.00	100
879639	2015-04-15	112.00	100
3104038	2015-06-06	112.00	100
2525861	2014-10-06	112.00	100
2220394	2015-10-14	112.00	100
1262082	2013-08-23	112.00	100
1916075	2015-08-10	112.00	100
3618375	2014-04-24	112.00	100
2510997	2016-05-02	112.00	100
1395776	2015-03-16	112.00	100
1479725	2013-06-03	112.00	100
1515312	2014-04-24	112.00	100
2548618	2013-11-06	112.00	100
398144	2015-03-07	112.00	100
2247349	2014-12-05	112.00	100
80891	2014-04-22	112.00	100
3616602	2013-10-10	112.00	100
759879	2013-02-11	112.00	100
1009724	2013-02-11	112.00	100
1600702	2013-04-16	112.00	100
541040	2014-04-26	112.00	100
293467	2014-04-26	112.00	100
2249080	2014-08-02	112.00	100
3427939	2013-03-19	112.00	100
802231	2015-08-22	112.00	100
3065953	2015-12-18	112.00	100
2298675	2013-06-26	112.00	100
1396345	2015-07-18	112.00	100
1956982	2014-01-29	112.00	100
969380	2015-04-22	112.00	100
1982514	2015-12-18	112.00	100
809705	2016-01-04	112.00	100
2524449	2013-03-11	112.00	100
3154751	2015-03-19	112.00	100
3450356	2013-05-08	112.00	100
2550706	2015-11-16	112.00	100
3450353	2013-05-02	112.00	100
969301	2016-01-04	112.00	100
3450343	2014-01-29	112.00	100
2299049	2015-04-22	112.00	100
3612812	2015-03-20	112.00	100
442951	2015-12-15	112.00	100
3155417	2015-07-18	112.00	100
1487362	2015-10-20	112.00	100
3066561	2014-02-26	112.00	100
395429	2015-12-18	112.00	100
717350	2013-12-09	112.00	100
2299357	2015-12-18	112.00	100
1514505	2015-08-20	112.00	100
1514516	2015-08-22	112.00	100
3144485	2014-02-26	112.00	100
3612246	2015-03-03	112.00	100
1486722	2015-01-14	112.00	100
1486575	2014-02-14	112.00	100
3527620	2014-04-22	112.00	100
1846919	2014-04-24	112.00	100
945175	2016-05-11	112.00	100
969164	2016-01-04	112.00	100
1279696	2014-09-25	112.00	100
2603133	2015-08-28	112.00	100
900192	2013-11-11	112.00	100
1486316	2016-01-04	112.00	100
3009850	2014-12-10	112.00	100
2175802	2016-05-11	112.00	100
1202730	2015-07-16	112.00	100
2986381	2015-08-10	112.00	100
2218026	2015-09-08	112.00	100
3430529	2015-02-25	112.00	100
2494513	2015-08-22	112.00	100
2989017	2015-08-26	112.00	100
1328286	2014-09-12	112.00	100
1459069	2014-03-05	112.00	100
3092091	2014-08-02	112.00	100
2807034	2015-12-09	112.00	100
918950	2014-11-10	112.00	100
498395	2013-06-20	112.00	100
3332155	2015-10-14	112.00	100
3092303	2015-05-21	112.00	100
498799	2014-09-25	112.00	100
1459786	2014-08-02	112.00	100
3092447	2015-03-16	112.00	100
2494900	2015-08-26	112.00	100
3101547	2015-09-26	112.00	100
1460157	2015-09-26	112.00	100
1322676	2015-06-06	112.00	100
496393	2015-11-11	112.00	100
1881766	2015-11-11	112.00	100
609494	2016-02-20	112.00	100
2235046	2015-03-03	112.00	100
2250333	2014-12-10	112.00	100
2469529	2013-02-11	112.00	100
1480394	2015-01-13	112.00	100
2986750	2013-03-11	112.00	100
2067658	2015-05-21	112.00	100
595172	2014-09-12	112.00	100
2469198	2014-01-06	112.00	100
2493456	2015-08-10	112.00	100
2987088	2015-09-26	112.00	100
3102275	2014-08-18	112.00	100
3357068	2014-04-22	112.00	100
233660	2016-05-11	112.00	100
918248	2013-06-14	112.00	100
3464704	2015-10-20	112.00	100
440565	2015-06-06	112.00	100
2495887	2016-05-02	112.00	100
291109	2014-11-10	112.00	100
2115667	2013-07-25	112.00	100
1011648	2013-06-20	112.00	100
1011813	2014-02-14	112.00	100
918465	2013-07-23	112.00	100
142702	2015-03-16	112.00	100
862708	2015-07-29	112.00	100
2301734	2015-11-03	112.00	100
3102779	2015-08-28	112.00	100
182628	2015-09-26	112.00	100
311391	2015-03-03	112.00	100
2711887	2015-01-13	112.00	100
1322349	2016-05-02	112.00	100
184464	2015-10-06	112.00	100
1401030	2015-08-27	112.00	100
2526266	2015-09-26	112.00	100
867649	2016-02-10	112.00	100
185281	2015-10-09	112.00	100
3429722	2013-11-11	112.00	100
867775	2015-12-18	112.00	100
590917	2016-05-26	112.00	100
3665084	2016-03-01	112.00	100
1329996	2013-07-25	112.00	100
740082	2015-03-07	112.00	100
1825246	2013-07-25	112.00	100
1043007	2014-06-19	112.00	100
3031218	2013-07-23	112.00	100
3388111	2013-07-25	112.00	100
3633108	2014-11-10	112.00	100
2976997	2013-03-11	112.00	100
1071278	2015-08-28	112.00	100
3277597	2014-08-20	112.00	100
2181115	2014-03-12	112.00	100
1043431	2014-02-28	112.00	100
191760	2015-11-11	112.00	100
3665433	2015-03-07	112.00	100
1320717	2014-07-07	112.00	100
3030102	2014-09-25	112.00	100
1044085	2015-03-10	112.00	100
2122416	2013-09-19	112.00	100
2977445	2015-02-02	112.00	100
1665897	2014-12-17	112.00	100
28939	2013-06-20	112.00	100
2122423	2013-10-10	112.00	100
1310514	2014-12-17	112.00	100
792567	2013-12-23	112.00	100
1825857	2014-02-18	112.00	100
2846340	2015-11-11	112.00	100
3279411	2015-11-03	112.00	100
3389443	2013-06-03	112.00	100
3279663	2014-04-22	112.00	100
3019724	2015-12-09	112.00	100
150421	2015-04-22	112.00	100
1824983	2015-08-26	112.00	100
2123837	2015-07-16	112.00	100
753732	2013-07-25	112.00	100
392751	2015-07-29	112.00	100
985231	2016-02-10	112.00	100
2722792	2014-09-25	112.00	100
3515137	2013-04-12	112.00	100
58034	2013-12-09	112.00	100
1393081	2015-01-13	112.00	100
985666	2016-03-01	112.00	100
3390875	2015-03-19	112.00	100
753742	2013-09-19	112.00	100
753749	2013-10-10	112.00	100
3017898	2014-08-20	112.00	100

Observe the query execution plan (or actual plan).

Notice the actual vs. estimated rows for the @Order Table Scan now. 490k estimated vs. 490k rows actual rows. This is because the Atble Variable was materialized during compilation, and the actual cardinality was used to cerry on optimizing the query plan.

In turn, this improved estimation propagated up the plan, namely the chosen join algorithm (Hash Match) which are efficient for larger input tables. Also note that given the correct estimations, SQL Server determined that the query plan should be executed with parallelism.

As you can see from the execution times, the query with Table Variable Deferred Compilation finished much faster! From ~18s down to ~8s.

359 KiB Raw Blame History