Maybe I'm missing something. If you don't have the Item Id how would you
perform Readv without giving an Item Id?. If you want just the Item Id
then Readnext ID Else seems the easy way. Seems like a Catch 22.
BobJ

"Tony Gravagno" <address.is.in.posts (AT) removethis (DOT) com.invalid> wrote in
message news:qbb1m5p0sf2ab631f5h3mrcr9o6m06fovh (AT) 4ax (DOT) com...

"RJ" wrote:
Bob, the concept of ReadV/0 doesn't mean you're trying to get
information about the item ID. It means you're testing to see if the
item exists. See:
http://www.pickwiki.com/cgi-bin/wiki...ips_And_Tricks

It's a convention, a trick that people have coded into, but (not that
I've tried it anytime recently) I don't believe D3 supports this
trick. I know this particular trick has caused some sites difficulty
in migration - as use of many non-standard tricks will...

HTH
T

word of warning Revelation readv from xx,ID,0 returns the complete record

note: I havent tested other versions of MV yet.

Rich

Tony Gravagno wrote:

Richard Wilson warned:
I'm on uniData.

Since translate through attribute 0 returns the
entire record, I suspected that READV would, too.

Here's my test program, GBP TEST:

OPEN 'GBP' TO FV ELSE STOP 201,'GBP'
READV GOO FROM FV,'TEST',0 ELSE GOO = 'NO CAN READV'
CRT CHANGE(GOO,@AM,CHAR(13):CHAR(10))

Anybody wanna guess what the output of this
program might be?




spoiler... answer below...








It produces "1" (without the quotes.)

Maybe it's returning a Boolean?!?

--
frosty

On Jan 28, 7:43*pm, "frosty" <fros... (AT) bogus (DOT) tld> wrote:

CHANGE statement.

This is why it shouldn't be used - you won't get a compile-time error
when you migrate - the behaviour of your application will change.
Nasty stuff.

Why not write a little test process and test yourself??? Wouldn't take
much, and if you were REALLY so inclined, could also then look at the
impact or poorly sized files, as well as different file types (dynamic
springs to mind)

You will then have MEANINGFUL data for YOUR environment .... all for
little more than it took to write your email, and much less time than
it will take me to read the thread :-)

Hi
I am fascinated by the incredible number of opinions expressed here on a
totally pointless subject.
It is ridiculous to ever use writev or readv as it leads to chaos.
The simple rule to follow is always dimension all items as an array and
always equate every element of the array to a standard variable then always
refer to all variables by name.
Simple bug free and obvious.
Obviously one sets up a schema for each item and includes it into each
program requiring the record. Then when a file changes as they do over time
it matters not if address1 is now attribute 13 when it was previously
attribute 7
Peter McMurray

"Ross Ferris" <rossf (AT) stamina (DOT) com.au> wrote

It depends on what system you are using. If READV doesn't recognise
field zero as being something special, it is likely to return the
entire record (as in Revelation).

UniVerse takes the THEN clause and returns the record id if the record
exists, and takes the ELSE clause and returns a null string if it
doesn't exist.

Unidata appears to return 1 or 0 as the "record" read though their
documentation isn't too clear on what is supposed to happen.

QM behaves like UniVerse though I notice that our documentation
doesn't quite match with this. It will be fixed.

Ultimately, READV fields 0 is implementation specific but, in all
systems that support it, it allows a program to determine whether a
record exists. I cannot say what happens in other systems but QM
certainly does not read the record into memory for this operation,
providing significant performance advantages over a READ when the
record is huge. A quick experiment with an 80Mb record in UniVerse
suggests it does the same.


Martin Phillips, Ladybridge Systems

I'm not sure I agree with this simple rule. I've really learned to
love dynamic arrays over the years.

Nothing worse than modifying an old system and having to change the
DIM statements all over the place.

You can still do equates if you wish.


always
refer to all variables by name.