Insert, Update & Delete Performance

Joe Changjchang6@yahoo.com

Insert, Update and DeleteInsert, Update and Delete

IUD BasicsMulti-row Inserts

Logical IO count

IUD Operations and Indexes

IUD Operations and Foreign Keys

Insert Plan – 1 RowInsert Plan – 1 Row

Insert Table(…)Values(…)

No indexes other than primary key

No foreign keys

Insert – I/O CostInsert – I/O Cost

Note: difference in I/O cost

Insert I/O cost dependsOn number of row in table!

0 & 1 row

> 300 rows

Insert Plan I/O Cost versus RowsInsert Plan I/O Cost versus Rows

0.010

0.012

0.014

0.016

0.018

1 10 100rows

Inse

rt I

/O C

ost

0.0100

0.0101

0.0102

0.0103

0.0104

0.0105

10 100 1000 10000rows

Inse

rt I

/O C

ost

320 r/p

99 r/p

I/O cost

Insert – Clustered IndexInsert – Clustered Index

Clustered index more or less same as Table

> 320 rows

Insert Plan Cost & Logical I/OInsert Plan Cost & Logical I/O

Logical I/O count1st rowTable 'MIC_01'. Scan count 0, logical reads 4, physical reads 0, read-ahead reads 0.2nd rowTable 'MIC_01'. Scan count 0, logical reads 2, physical reads 0, read-ahead reads 0.Row ~65,000Table 'MIC_01'. Scan count 0, logical reads 3, physical reads 0, read-ahead reads 0.

Insert Cost FormulaI/O: 0.010068378 to 0.016756756CPU: 0.00000100 per rowTotal: 0.010070635 to 0.016759014

Plan cost independent of indexes at low row counts

Disk SettingDisk Setting

Enable Write Caching andEnable Advanced Performancehas large impact on log writeperformance

1) Write to disk, continue after confirmation

2) Write to disk, continue immediately

Settings vary fromWindows 2000 ServerWindows XPWindows Server 2003

INSERT & Physical DiskINSERT & 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?

BEGIN/COMMIT TRANBEGIN/COMMIT TRAN

Which is faster and more efficient?

WHILE @I < 100,000 BEGIN INSERT Table(…) VALUES (@I, …) SET @I = @I + 1END

BEGIN TRANSACTION WHILE @I < 100,000 BEGIN INSERT Table(…) VALUES (@I, …) SET @I = @I + 1 ENDCOMMIT TRANSACTION

A

B

Update 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

Table Update – Index SeekTable Update – Index Seek

Same as plain Index Seek

Table Update – CS & TopTable Update – CS & Top

CPU: 0.0000001 / row

CPU: 0.0000001 / row

Table UpdateTable Update

Clustered Index UpdateClustered Index Update

Single component, but numbers don’t add up

Update Plan CostUpdate Plan Cost

Same cost structure as Insert plus additional Index Seek cost(I/O costs depend on Table density and row count)

Clustered IndexI/O: 0.010068378CPU: 0.00000100 per rowTotal: 0.016477678

TableIndex Seek: 0.0064081Compute Scalar: 0.0000001Top: 0.0000001Table Update I/O: 0.010071216

CPU: 0.00000100Total: 0.016480517

Index Seek cost implied?

DeleteDelete

DeleteDelete

Multi-row InsertsMulti-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'

Multi-row Inserts – Union AllMulti-row Inserts – Union All

INSERT N1C(ID,Value) SELECT 321,'TYI539087J‘UNION ALL SELECT 322,'TYI539087J'

Multi-row InsertsMulti-row Inserts

Multi-row InsertsMulti-row Inserts

2 rows

CPU: 2XI/O: same

Multi-row InsertsMulti-row Inserts

Multi-row SelectMulti-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 = @ID1SELECT @Value2 = VALUE FROM M2C WHERE ID = @ID2

Plan Cost is lower than 2 separate selects, but actual performance is worse!

Multi-row DeleteMulti-row Delete

DECLARE @ID1 int, @ID2 int SELECT @ID1 = 1, @ID2 = 49999

DELETE MIC WHERE ID IN (@ID1,@ID2)

Has not been tested!

IUD with Additional IndexesIUD with Additional Indexes

IUD ops may need to modify indexesInsert & 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

Inserts with indexes - I/O countInserts with indexes - I/O count

Index depth: Clustered 2, Nonclustered 1

No indexes other than primary keyTable 'MIC'. Scan count 0, logical reads 2, physical reads 0, read-ahead reads 0.

1 Nonclustered indexTable 'MIC'. Scan count 0, logical reads 3, physical reads 0, read-ahead reads 0.

2 Nonclustered indexesTable '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

Insert with Select QueryInsert with Select Query

Primary key – clustered, and 1 nonclustered index

Up to ~500 rows

INSERT MIC(…) SELECT … FROM M2C

> ~505 rowsSELECTINSERT

Multiple IndexesMultiple Indexes

Update w/IX, large row countUpdate w/IX, large row count

600 rows

Update multiple IX, large row countUpdate multiple IX, large row count

One for each index excluding PK

Spool & SequenceSpool & Sequence

Spool I/O 0.008752485 + 0.0074975/pageSpool CPU 0.00000040 + 0.000000360/row

Sequence CPU 0.0000020/row

Delete w/Index large row countDelete w/Index large row count

505 rows

1 NC Index

2 NC Indexes

Foreign KeysForeign 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

Insert w/Foreign Key ConstraintInsert 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

Insert FK details

Delete w/FK ConstraintDelete 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

Delete–FK & Table Scan comparedDelete–FK & Table Scan compared

FK

PK

Delete – Reference Table ScanDelete – Reference Table Scan

Unusually low cost

Expected cost for 506 pages,50,000 rows

From Delete op FK Reference

From normal Table scan

Index on Foreign KeyIndex 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 = 50001Statistics IO:Table 'M2C'. Scan count 1, logical reads 4, physical reads 0, read-ahead reads 0.

Delete with Indexed Foreign KeyDelete 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

Update with Foreign KeyUpdate with Foreign Key

Update Primary Key table

Update Foreign Key table

FK

PK

FK

PK

Query Cost ModelQuery 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

INSERT CharacteristicsINSERT Characteristics

0

2,000

4,000

6,000

8,000

1 2 4 6 8 10Threads

RP

C/s

ec

Single row INSERTClustered index, no other indexesNo Foreign Keys2x2.4GHz server

050,000

100,000150,000200,000250,000300,000350,000400,000450,000

1 2 4 6 8 10Threads

CP

U-C

ycle

s

0%10%20%30%40%50%60%70%80%90%

Mea

n C

PU

Uti

l.

CPU-Cycles

CPU Util

Net CPU-cycles cost – excludes RPC cost

Clustered, Heap, Non-Clust.Clustered, Heap, Non-Clust.

0

100,000

200,000

300,000

400,000

500,000

1 2 4 6 8 10Threads

CP

U-C

ycle

s

Clustered

Heap

Non Clustered

Single row INSERT 1) Clustered index 2) Heap with no indexes 3) Heap with 1 non-clustered index

Log write consolidation?

Context switch reduction?

INSERT – Multiple RowsINSERT – Multiple Rows

0

5,000

10,000

15,000

20,000

25,000

1 2 4 6 8 10Insert Statements per Stored Proc

RPC/sec

Inserts/sec

Multiple single row INSERT statements per stored proc8 threads

0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

1 2 4 6 8 10

Insert rows per Stored Proc

RPC/sec

Insert rows/sec

Multiple rows per INSERT statement (UNION ALL)8 threads

IUD Cost StructureIUD Cost Structure

P4/Xeon* Notes

RPC cost 240,000 Higher for threads, owner m/m

Type Cost 130,000 once per procedureIUD Base 170,000 once per IUD statementSingle row IUD 300,000 Range: 200,000-400,000

Multi-row InsertCost per row 90,000 cost per additional row

*Use Windows NT fibers on

INSERT, UPDATE & DELETE cost structure very similarMulti-row UPDATE & DELETE not fully investigated

INSERT Cost StructureINSERT Cost Structure

Index and Foreign Key not fully explored

Early measurements:

50-70,000 per additional index50-70,000 per foreign key

IUD SummaryIUD Summary

Consolidate IUD statements where possible

Large impact on performance

Verify impact of BEGIN/COMMIT TRAN

REPEATABLE READ & SERIALIZABLE not tested

Index & Foreign Key overheadSome cost on IUD for each index

Most app 90% Read, 10% Write?

Is FK required for data integrity?

Test TablesTest 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 rowsIndex depth 299 row per page506 pages

Test DataTest Data

DECLARE @I int, @rowCnt int, @p int, @sc1 int, @dv1 intSELECT @I = 1, @rowCnt = 50000, @p = 100, @sc1 = 10SELECT @dv1 = @rowCnt/@sc1WHILE @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+1END

Test Data SequencesTest Data Sequences

WHILE loop variable @I: 1,2,3,…

Function Sequence(@I-1)/10 + 1 increments every 10 rows(@I-1)%(10) + 1 10 distinct values repeating

1,2,3,4,5,6,7,9,10,1,2,3

LinksLinks

www.sql-server-performance.com/joe_chang.asp

SQL Server Quantitative Performance AnalysisSQL Server Quantitative Performance AnalysisServer System ArchitectureServer System ArchitectureProcessor PerformanceProcessor PerformanceDirect Connect Gigabit NetworkingDirect Connect Gigabit NetworkingParallel Execution PlansParallel Execution PlansLarge Data OperationsLarge Data OperationsTransferring StatisticsTransferring StatisticsSQL Server Backup Performance with Imceda LiteSpeedSQL Server Backup Performance with Imceda LiteSpeed

jchang6@yahoo.com