RE: %lookup vs. chain

[Mike Haston ** Data <MJH@xxxxxxx>]

It turns out that I'll probably change my programming a bit.  I have an SQL
statement that I can add and ORDER BY ACCT# to and then just chain out when
the ACCT# changes.  Previously I pull in information on about 35 customers
that we receive a certain EDI document from.  The records come in any order,
so I was checking this flag with each record that I read.

Thanks for the input.


-----Original Message-----
From: Scott Klement [mailto:klemscot@klements.com]
Sent: Friday, November 22, 2002 10:59 AM
To: 'midrange-l@midrange.com'
Subject: Re: %lookup vs. chain



How big is the control file?

Will you be adding data to the control file as you process the large
files?

Will the control file be sorted, so that %lookup() can search it
efficiently?

For a small control file that's already sorted, the %lookup BIF should be
much faster than CHAIN.   For a large file, especially if it's not sorted,
CHAIN would be better...  But, of course, you could always sort it.

Finally, if you'll be adding to the array frequently, then having to
re-sort it, that could affect performance.

A user-index might be another alternative.


On Fri, 22 Nov 2002, Mike Haston ** Data wrote:

> I'm just noticing that as I spin through some large files that I'm
chaining
> out a million times (actually more) to a control file to check a flag.  In
> the initial subroutine I'm setting up an array that I could easily store
> this flag in.  I'm wondering what the opinion is as far as
performance-wise
> which is more efficient, doing the %lookup() on the array or chain to the
> file?
>

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