1. Insert, Update & Delete Performance Joe Chang jchang6@yahoo.com

2. Insert, Update and Delete IUD Basics Multi-row Inserts Logical IO count IUD Operations and Indexes IUD Operations and Foreign Keys

3. Insert Plan – 1 Row Insert Table(…) Values(…) No indexes other than primary key No foreign keys

4. Insert – I/O Cost Note: difference in I/O cost Insert I/O cost depends On number of row in table! 0 & 1 row > 300 rows

5. Insert Plan I/O Cost versus Rows I/O cost

6. Insert – Clustered Index Clustered index more or less same as Table > 320 rows

7. Insert Plan Cost & Logical I/O Logical I/O count 1 st row Table 'MIC_01'. Scan count 0, logical reads 4, physical reads 0, read-ahead reads 0. 2 nd row Table 'MIC_01'. Scan count 0, logical reads 2, physical reads 0, read-ahead reads 0. Row ~65,000 Table 'MIC_01'. Scan count 0, logical reads 3, physical reads 0, read-ahead reads 0. Insert Cost Formula I/O: 0.010068378 to 0.016756756 CPU:0.00000100 per row Total:0.010070635 to 0.016759014 Plan cost independent of indexes at low row counts

8. Disk Setting Enable Write Caching and Enable Advanced Performance has large impact on log write performance 1)Write to disk, continue after confirmation 2)Write to disk, continue immediately Settings vary from Windows 2000 Server Windows XP Windows Server 2003

9. INSERT & Physical Disk Each standalone INSERT statement must be matched to 1 or more write I/Os to transaction log, may or may not result in write to data, SQL Server may consolidate transaction log entries from separate threads (Process ID or SPIDs) into a single I/O on the transaction log file Log writes for statements inside BEGIN/COMMIT TRANSACTION are consolidated?

10. BEGIN/COMMIT TRAN Which is faster and more efficient? WHILE @I < 100,000 BEGIN INSERT Table(…) VALUES (@I, …) SET @I = @I + 1 END BEGIN TRANSACTION WHILE @I < 100,000 BEGIN INSERT Table(…) VALUES (@I, …) SET @I = @I + 1 END COMMIT TRANSACTION A B

11. Update UPDATE N1N SET Value = 'ABC123456D‘ WHERE ID = 1 UPDATE MXN SET ID9 = 1 WHERE ID = 1 Non integer values No Compute Scalar for Updates to Clustered Index

12. Table Update – Index Seek Same as plain Index Seek

13. Table Update – CS & Top CPU: 0.0000001 / row

14. Table Update

15. Clustered Index Update Single component, but numbers don’t add up

16. Update Plan Cost Same cost structure as Insert plus additional Index Seek cost (I/O costs depend on Table density and row count) Clustered Index I/O: 0.010068378 CPU:0.00000100 per row Total:0.016477678 Table Index Seek: 0.0064081 Compute Scalar:0.0000001 Top:0.0000001 Table Update I/O:0.010071216 CPU:0.00000100 Total:0.016480517 Index Seek cost implied?

17. Delete

18. Delete

19. Multi-row Inserts Compare two separate Insert statements: INSERT N1C(ID,Value) VALUES (321,'TYI539087J') INSERT N1C(ID,Value) VALUES (322,'TYI539087J') With statement below INSERT N1C(ID,Value) SELECT 321,'TYI539087J‘ UNION ALL SELECT 322,'TYI539087J'

20. Multi-row Inserts – Union All INSERT N1C(ID,Value) SELECT 321,'TYI539087J‘ UNION ALL SELECT 322,'TYI539087J'

21. Multi-row Inserts

22. 2 rows CPU: 2X I/O: same

23. Multi-row Inserts

24. Multi-row Select SELECT @Value1 = CASE ID WHEN @ID1 THEN VALUE ELSE @Value1 END, @Value2 = CASE ID WHEN @ID2 THEN VALUE ELSE @Value2 END FROM M2C WHERE ID IN (@ID1,@ID2) SELECT @Value1 = VALUE FROM M2C WHERE ID = @ID1 SELECT @Value2 = VALUE FROM M2C WHERE ID = @ID2 Plan Cost is lower than 2 separate selects, but actual performance is worse!

25. Multi-row Delete DECLARE @ID1 int, @ID2 int SELECT @ID1 = 1, @ID2 = 49999 DELETE MIC WHERE ID IN (@ID1,@ID2) Has not been tested!

26. IUD with Additional Indexes IUD ops may need to modify indexes Insert & Delete – always Update – only if modified value is in index Plan costs for low row counts Not dependent on indexes Counter intuitive, but plan not impacted IUD w/larger row counts Plan depends on indexes

27. Inserts with indexes - I/O count Index depth: Clustered 2, Nonclustered 1 No indexes other than primary key Table 'MIC'. Scan count 0, logical reads 2, physical reads 0, read-ahead reads 0. 1 Nonclustered index Table 'MIC'. Scan count 0, logical reads 3, physical reads 0, read-ahead reads 0. 2 Nonclustered indexes Table 'MIC'. Scan count 0, logical reads 4, physical reads 0, read-ahead reads 0. 2 I/O for Clustered Index (Index Depth 2) 1 I/O for each nonclustered index at Index Depth 1

28. Insert with Select Query Primary key – clustered, and 1 nonclustered index Up to ~500 rows INSERT MIC(…) SELECT … FROM M2C > ~505 rows SELECT INSERT

29. Multiple Indexes

30. Update w/IX, large row count 600 rows

31. Update multiple IX, large row count One for each index excluding PK

32. Spool & Sequence Spool I/O 0.008752485 + 0.0074975/page Spool CPU 0.00000040 + 0.000000360/row Sequence CPU 0.0000020/row

33. Delete w/Index large row count 505 rows 1 NC Index 2 NC Indexes

34. Foreign Keys ALTER TABLE [dbo].[M2C] ADD CONSTRAINT [FK_M2C_M2D] FOREIGN KEY ( [ID2] ) REFERENCES [dbo].[M2D] ( [ID] ) ON DELETE NO ACTION ON UPDATE NO ACTION

35. Insert w/Foreign Key Constraint INSERT M2C (…) VALUES (50001,…) Statistics IO: Table 'M2D'. Scan count 1, logical reads 2, physical reads 0, read-ahead reads 0. Table 'M2C'. Scan count 0, logical reads 2, physical reads 0, read-ahead reads 0. Index depth 2, both tables FK PK

36. Insert FK details

37. Delete w/FK Constraint DELETE M2D WHERE ID = 50001 Statistics IO: Table 'M2C'. Scan count 1, logical reads 507, physical reads 0, read-ahead reads 0. Table 'M2D'. Scan count 1, logical reads 2, physical reads 0, read-ahead reads 0. 506 leaf level pages FK PK

38. Delete–FK & Table Scan compared FK PK

39. Delete – Reference Table Scan Unusually low cost Expected cost for 506 pages, 50,000 rows From Delete op FK Reference From normal Table scan

40. Index on Foreign Key CREATE INDEX IX_M2C_ID2 ON M2C(ID2) INSERT M2C (…) VALUES (50001,…) Statistics IO: Table 'M2D'. Scan count 1, logical reads 2, physical reads 0, read-ahead reads 0. Table 'M2C'. Scan count 0, logical reads 4, physical reads 0, read-ahead reads 0. DELETE M2C WHERE ID = 50001 Statistics IO: Table 'M2C'. Scan count 1, logical reads 4, physical reads 0, read-ahead reads 0.

41. Delete with Indexed Foreign Key DELETE M2D WHERE ID = 50001 Statistics IO: Table 'M2C'. Scan count 1, logical reads 2, physical reads 0, read-ahead reads 0. Table 'M2D'. Scan count 1, logical reads 2, physical reads 0, read-ahead reads 0. FK PK

42. Update with Foreign Key Update Primary Key table Update Foreign Key table FK PK FK PK

43. Query Cost Model Actual Query Costs in CPU-Cycles Stored Procedure Cost = RPC cost (once per procedure) + Type cost (once per procedure?) + Query cost (once per query) Query – one or more components Component Cost = + Component base cost + Additional row or page costs

44. INSERT Characteristics Single row INSERT Clustered index, no other indexes No Foreign Keys 2x2.4GHz server Net CPU-cycles cost – excludes RPC cost

45. Clustered, Heap, Non-Clust. Single row INSERT 1) Clustered index 2) Heap with no indexes 3) Heap with 1 non-clustered index Log write consolidation? Context switch reduction?

46. INSERT – Multiple Rows Multiple single row INSERT statements per stored proc 8 threads Multiple rows per INSERT statement (UNION ALL) 8 threads

47. IUD Cost Structure P4/Xeon*Notes RPC cost 240,000Higher for threads, owner m/m Type Cost 130,000once per procedure IUD Base 170,000once per IUD statement Single row IUD300,000Range: 200,000-400,000 Multi-row Insert Cost per row 90,000cost per additional row *Use Windows NT fibers on INSERT, UPDATE & DELETE cost structure very similar Multi-row UPDATE & DELETE not fully investigated

48. INSERT Cost Structure Index and Foreign Key not fully explored Early measurements: 50-70,000 per additional index 50-70,000 per foreign key

49. IUD Summary Consolidate IUD statements where possible Large impact on performance Verify impact of BEGIN/COMMIT TRAN REPEATABLE READ & SERIALIZABLE not tested Index & Foreign Key overhead Some cost on IUD for each index Most app 90% Read, 10% Write? Is FK required for data integrity?

50. Test Tables CREATE TABLE [dbo].[M2C] ( [ID] [int] NOT NULL, [ID2] [int] NOT NULL, [ID3] [int] NOT NULL, [ID4] [int] NOT NULL, [ID5] [int] NOT NULL, [ID6] [int] NOT NULL, [GroupID] [int] NOT NULL, [CodeID] [int] NOT NULL, [Value] [char] (10) NOT NULL, [randDecimal] [decimal](9, 4) NOT NULL, [randMoney] [money] NOT NULL, [randDate] [datetime] NOT NULL, [seqDate] [datetime] NOT NULL ) ON [PRIMARY] 50,000 rows Index depth 2 99 row per page 506 pages

51. Test Data DECLARE @I int, @rowCnt int, @p int, @sc1 int, @dv1 int SELECT @I = 1, @rowCnt = 50000, @p = 100, @sc1 = 10 SELECT @dv1 = @rowCnt/@sc1 WHILE @I <= @RowCnt BEGIN INSERT M2C (ID, ID2, ID3, ID4, ID5, ID6, GroupID, CodeID, Value, randDecimal, randMoney, randDate, seqDate) VALUES ( @I, @I, 1 + (@I-1)*@p/@rowCnt + ((@I-1)*@p)%@rowCnt, @I/4, @I/10, (@I-1)%(320) + 1, (@I-1)/@sc1 + 1, (@I-1)%(@dv1) + 1, CHAR(65+26*rand())+CHAR(65+26*rand())+CHAR(65+26*rand()) +CONVERT(char(6), CONVERT(int,100000*(9.0*rand()+1.0)))+CHAR(65 + 26*rand()), 10000*rand(), 10000*rand(), DATEADD(hour,120000*rand(),'1990-01-01'), DATEADD(hour,3*@I,'1990-01-01') ) SET @I = @I+1 END

52. Test Data Sequences WHILE loop variable @I: 1,2,3,… FunctionSequence (@I-1)/10 + 1increments every 10 rows (@I-1)%(10) + 110 distinct values repeating 1,2,3,4,5,6,7,9,10,1,2,3

53. Links www.sql-server-performance.com/joe_chang.asp SQL Server Quantitative Performance Analysis Server System Architecture Processor Performance Direct Connect Gigabit Networking Parallel Execution Plans Large Data Operations Transferring Statistics SQL Server Backup Performance with Imceda LiteSpeed jchang6@yahoo.com