Four Hundred Guru--Sorting Arrays and Subfiles with a User Index

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Volume 7, Number 4 -- January 31, 2007

Sorting Arrays and Subfiles with a User Index

Published: January 31, 2007

Hey, Ted:

I'd like to suggest another method Jennifer can use for sorting arrays. Why not use a user index? I use user indexes so the user may sort subfiles umpteen different ways. Using a user index eliminates the need to be concerned with size (unless you have more than 4 GB of data). Maybe size would not be an issue in Jennifer's daily run shipping application.

--Drew at BIC Graphic USA

Note: the code from this article is available for download

Drew sent me some illustrative code and a short write-up about the three API's he uses--Create a User Index (QUSCRTUI), Add User Index Entries (QUSADDUI), and Retrieve User Index Entries (QUSRTVUI). I fleshed out the code, adding the calculations to read file QCUSTCDT (an example file you will find in library QIWS) and print out the sorted data. You can download the code here. It should compile and run, sorting the data on customer number. Here's the output I got.

192837    Lee      F L Hector 
389572    Stevens  K L Denver 
392859    Vine     S S Broton 
397267    Tyron    W E Hector 
475938    Doe      J W Sutter 
583990    Abraham  M T Isle   
593029    Williams E D Dallas 
693829    Thomas   A N Casper 
839283    Jones    B D Clay   
846283    Alison   J S Isle   
938472    Henning  G K Dallas 
938485    Johnson  J A Helen

It's worth taking a minute to look at the parameter lists for the APIs, so I've included Drew's tables below. Once you've set them up in one program, they should be easy to adapt to other programs. Also, I recommend you check out Bruce Guetzkow's article on user indexes. The link to that story is below in the Related Stories section.

--Ted

QUSCRTUI--Create User Index

Parameter	Description
IndexName	Name of index - user name plus QTEMP library
ExtendAtr	Blanks for the extended attribute
EntLenAtr	‘F’ for fixed length – can also be ‘V’ for variable length
EntLength	Length of the index data
KeyInsert	‘1’ for insertion by key – can also be ‘0’ for no insertion by key
KeyLength	Length of key
ImmdUpdat	‘1’ for immediate update – can also be ‘0’ for no immediate update
Optimize	‘1’ for optimize for sequential references – can also be ‘0’ for optimize for random references
PubAuthor	‘*ALL’ for allowing user to perform all operations on the index
TextDesc	Text description of the index
Replace	‘*YES’ for replace index of the same name and library
APIError	Error data structure

QUSADDUI--Add User Index Entries

Parameter	Description
ReturnLib	Name of library of index which entries were added
NumbAdded	Number of entries successfully added
IndexName	Name of index – user name plus QTEMP library
ActionType	Type of insert to be performed – 3 for insert without replacement – can also be 1 for insert for non-key or 2 for insert with replacement
IndexData	Actual entry or entries – name of data structure that holds the data
IndexLen	Length of entry of entries
LenOffSet	Used for variable length indexes
NumbEntry	Number of entries to be added
APIError	Error data structure

QUSRTVUI--Retrieve User Index Entries

Parameter	Description
RcvVar	The variable that is to receive the data – name of the data structure
RcvVarLen	Length of the receiver variable
RcvLenOff	Entry offset used to parse through the receiver variable
RcvVarOffL	Length of entry offset
NumbReturn	Number of entries returned
ReturnLib	Name of library of index which entries were retrieved
IndexName	Name of index – user name plus QTEMP library
FmtName	Format of index information – IDXE0100
MaxNbrEnt	Maximum number of entries to be returned
SearchType	Type of search to be performed – 2 for greater than – can also be 1 for equal, 3 for less than, 4 for greater than or equal, 5 for less than or equal, 6 for first, 7 for last, and 8 for between
SearchKey	Search criteria – the key
SearchLen	Length of the search criteria
SearchOff	Search criteria offset – *Zero – ignored unless search type is 8
APIError	Error data structure

Note: When index records are returned, ignore the first eight bytes of data (contain some type of hex index information).

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Senior Technical Editor: Ted Holt

Technical Editors: Howard Arner, Joe Hertvik, Shannon O'Donnell, Kevin Vandever

Contributing Technical Editors: Joel Cochran, Wayne O. Evans, Raymond Everhart,
Bruce Guetzkow, Brian Kelly, Marc Logemann, David Morris

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Finding the Last Transaction for a Customer Sorting Arrays and Subfiles with a User Index When Fix Central Won't Let You Download PTFs

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