gerry-u2ug wrote:
is this true ? I have never experienced the slowdown of the initial
"traversal" and can't see the need for it - this statement just uses a
different select list other than zero. now if the question had been regarding SELECTV
rather than SELECT, then I would agree.
Gerry
Mea culpa!
As there's no way you can assign the resulting select list to a
variable without
first 'traverse' the file - that is without at least read the list of
record-id
in each page ( or hash point ) I jumped to the conclusion that there
would be..
But evidently the implementation is such as the variable is not assigned
to/with/as
the full list before the program continues with the loop.
That also explains why you can't do much else than readnext with
a list variable - dcount it for example.
Took a large file used both methods and printed the first
readnext'ed id and timed it for proof - both ways printed
emediately.
(But I had to SELECTV for the list variable case )
-- mats
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] Behalf Of Mats Carlid
Sent: Thursday, July 14, 2005 06:22 AM
To: u2-users@listserver.u2ug.org
Subject: Re: [U2] [UV] Select Question
I'm aware of two differences that may be of importance
- if we're speaking uv -
The LIST alternative is immune to a secondary select
inside the loop - possibly well hidden in an itype in
a subroutine of an subr....
The bare select lets the readnext loop start emediately
and saves (probably) one traversal of the file.
So yes You'd save overhead - lot's of wall clock time
and io but probably not that much cpu.
hth
-- mats
[EMAIL PROTECTED] wrote:
Hi all,
Can someone tell me the diference between the following two examples of
executing an external select?
SELECT FILE TO LIST
LOOP
READNEXT ID FROM LIST ELSE ID = @AM
UNTIL ID = @AM DO
REPEAT
SELECT FILE
LOOP
READNEXT ID ELSE ID = @AM
UNTIL ID = @AM DO
REPEAT
Someone pointed out to me that there is overhead in selecting to a list that I
need not be exposing myself to. Aren't they both kind of reading from a list
somewhere anyways?
Thanks
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