Routines Advance 3

8/8/2019 Routines Advance 3

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Routines(Transform Functions)

DataStage


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The Process

Identify Need

does something already exist?

Specification business rules

Design

algorithm selection

name of function (must be unique in project)


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Example 1

Identify need

need to encode weekdays as TinyInt

DayofWeek function exists in Dev category

StringDecode function exists in SDK\String

need high performance (rapid return)


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Example 1

Specification

week begins on Sunday, which is day 1

week ends on Saturday, which is day 7

invalid input (not day name) returns zero

input is not case sensitive


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Example 1

Design

existing DayofWeek function is case sensitive(so does not suit requirement)

however this routine may be able to subsumefunctionality of DayofWeek (and thereforereplace it)

StringDecode requires passing searchablestructure every row; cumbersome (slow?)


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DayofWeekAns =0

InputArg = TrimB(InputArg)Begin Case

Case InputArg = "MONDAY"

Ans= 2

Case InputArg = "TUESDAY"

Ans= 3

Case InputArg = "WEDNESDAY"Ans= 4

Case InputArg = "THURSDAY"

Ans= 5

Case InputArg = "FRIDAY"

Ans= 6

Case InputArg = "SATURDAY"Ans= 7

Case InputArg = "SUNDAY"

Ans= 1

Case @True ;* all other values

Ans = -1

End CaseRETURN(Ans)


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StringDecode


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Example 1

Design possible algorithms

Iconv(DayName, "DWA")

does this work? how to test?

StringDecode function (SDK\String)

Case construct (as in DayofWeek)

positional field search (as in StringDecode)

positional field search using static variables


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Algorithm Selection

Document pro's and con's

Document decision


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Example 1

Algorithm Pro Con

Iconv(x, "DWA") Doesn't work

StringDecode Exists, works Slow

DayofWeek Exists, works Case sensitive

Case Works Slow

Field search Works Already exists

Field search static Fast


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Creating Transform Functions

DataStage


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Creating Transform Function

Select Routinesbranch

New server routine

Ensure routine typeis "TransformFunction"


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General tab

Name

meaningful

Category

standards? Short desc

helps futureselection

Long desc

purpose,business rules,special conditions


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Creator tab

Why?

so they knowwho to ask

Update at eachmodification

Version 2.0.0

may bechanged by

developer,Version Control


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Arguments tab

Argumentname

standards?

meaningful

Description

assists

future usersof Routine


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Code tab

We will returnto the code tabshortly


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Dependencies tab

If Routine callsother Routines,record the others

here checklist for

deployment


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Code tab

Function declaration filled in with arguments

RETURN(Ans) function filled in

your code must assign a value to Ans variable

History block


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Code tab


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0

Some Rules

Function must return to caller

proper operation of DataStage depends on it

you must not use any of the followingstatements

DSLogFatal Chain

Stop Debug

Abort


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Example (continued)

Documentreason forunusual

techniques Format

source code


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Example (continued)

Documentreason forunusual

techniques Save button

enabled


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Example (continued)

Save sourcecode

Compile

buttonenabled


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Example (continued)

Compilesourcecode


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Example (continued)

Resultdisplayed

correcterrors

Testenabled


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Exercise

Let's Do One Together


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Need: Determine Week Number

Business Rules

expected input (date?) (exceptions?)

expected output (WEEK.TAG?)

definition of week number 1 in year


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Specification

Business rules

Week begins on Sunday

Week number 1 begins on first Sunday inJanuary

Expected input is internal format date

return "" otherwise, or NULL if input NULL

Expected output is WEEK.TAG see Data Element for definition (yyyyWnn)


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Thought Process

What is week number today?

How did you calculate it?

Inspect calendar for January

identify week number 1

Document "business rule"

Get Business Analyst to verify

if appropriate


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Sample Rules

Business rules

Week begins on Sunday

Week number 1 begins on first Sunday inJanuary


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Algorithm Development

Algorithm

(FirstSundayYear)-(SundayThisWeek)

((FirstSundayYear)-(SundayThisWeek)) / 7

Int(((FirstSundayYear)-(SundayThisWeek)) / 7)

Int(((FirstSundayYear)-(SundayThisWeek)) / 7)

+ 1

Adjust for days earlier then (FirstSundayYear),which will be in week 53 of prior year.

days

weeks

integer

week#


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Algorithm Development

How to calculate Sunday of this week?

internal format dates, Mod(Sunday,7) = 0

therefore TheDate Mod(TheDate,7)

How to calculate first Sunday in year?

Iconv(01/01/yyyy, "D") + N


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Demonstration

DataStage Manager


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Creating New Routine

Tip: Start indesiredcategory;category filledin for you


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New Routine Created

Ensure that routinetype is TransformFunction


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General Tab

Meaningful name

Short description

Long description

Anotherdeveloper could take over now; your intentions are clear.


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Creator Tab

Author keptupdated

Future developer

knows where toseek advice


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Arguments Tab

Meaningful name

Description can bemulti-line

Ctrl Enter forline break


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Code Tab (1)

History block

Commentsshowing purpose,

etc.


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Code Tab (2)

Initialize Ansvariable

Handle abnormal

input could test at thispoint


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Code Tab (3)

Documentreason forchoosingunusualalgorithm


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Code Tab (4)

Outline algorithmusing commentsonly


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Code Tab (5)

Developalgorithm usingDataStageBASICstatements


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Save and Compile

Go backand fix anyerrors, save

andcompileagain


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Testing

Test Grid


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Test Using Test Grid

Generate testvalues to testnormal andabnormal

conditions


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Debugging Statements

Surround with$IFDEF and$ENDIF

Use$DEFINE


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Enable using$DEFINE

Save,compile, andtest


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Enableusing$DEFINE

Save,compile, andtest

Double-click

Results


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Ready for Production

Disable testingstatements using$UNDEFINE

Save, compile

controlledstatementsnot compiled

Routines Advance 3

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