QTP reads every row instead of using index?

[Herald.Kaffka at westfraser.com]

(Had to trim most of the history, size of this message thread of was 
getting too big for this list...).

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I also seem to remember something about "select file if" conditions short 
circuiting the build of a record complex,
(Select File if was supposed to kick in as soon as the file entered the 
record complex, and would prevent PH from
growing the record complex with unneeded records, while select  was 
evaluated "after all records were retreived").

Don't know if  this is an urban legend, an relic of an early PH version, 
or if there some truth to it...

To this day, (If I'm not working with a cursor), I still tend to 
"Choose" on the primary file, 
select file if as soon as possible on the other files in the access list 
(esp if selecting on some field condition in just that file such as 
"select inventory_balance if status of inventory_balance = "A").
and run a final select on cross table fields at the bottom. 

Don't know if really more efficient or not (at one time I was told it 
was),  but it does tend to make the logic on a large ugly join a little 
clearer (at least to me).
I'm not likely to change my style at this point, but I do idly wonder if 
"I'm right" or if it's just a "Crusty Old Guy" thing... 

(Or if the answer is like all good fairy tales and begins "once upon a 
time" this was correct, but after version x it doesn't matter any 
more...).

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Thanks!

A+

Etienne

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Think first, reply later.  (gotta remember that rule). 

There is/was an advantage to using Choose (or choose with select) on 
RMS/ISAM. 

The choose (which can only operate on the initial file on the access 
statement), can limit the size of the data set which 
is processed.  (You have to be choosing an indexed item, only items which 
match the choose criteria are driven down 
into the link x of table a to y of table b logic).  With just a select, 
all of table A will be read, POWERHOUSE will apply the 
select, and then use that to drive out the the other tables in the Join. 
If table A is very big, and the select is very selective, 
this can be a big difference, (read a million records, throw out the ones 
before yesterday, link the remaining 2000 records 
into a results set, as opposed to reading 2000 rows since yesterday 
(choose date(days(sysdate)-1)) and building the complex... 




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