Correct me if I'm wrong but won't hashing the same string produce the
same hash?? (which is the whole point of hashing a string to begin with) This
means if you can't truncate a unique identifier and be sure of uniqueness (which
you can't) hashing it or not hashing it will make no
difference
-
James
--------Original Message-----
From: Vaughan Allan [mailto:[EMAIL PROTECTED]
Sent: Thursday, September 11, 2003 4:24 PM
To: CFAussie Mailing List
Subject: [cfaussie] RE: a long shot...
Further to this - if you *REALLY* wanted to truncate a UUID and have some sort of uniqueness, hash() it first.
e.g.
<cfscript>
uuid = CreateUUID();
myhash = hash(uuid);
myid = left(myhash,16);
writeoutput(myid);
// or a shorter version:
// writeoutput(left(hash(createuuid()),16));
</cfscript>
Regards,
Vaughan.
"Darren Tracey" <[EMAIL PROTECTED]>
Sent by: [EMAIL PROTECTED]11/09/2003 04:02 PM
"CFAussie Mailing List" <[EMAIL PROTECTED]>
"CFAussie Mailing List" <[EMAIL PROTECTED]> [cfaussie] RE: a long shot...
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Sent: Thursday, 11 September 2003 2:36 PM
To: CFAussie Mailing List
Subject: [cfaussie] a long shot...
The field is of datatype varchar (16), so if I was to use createUUID() to arrive at the value, would i be assured that the final 16 characters of the UUID generated by CF is going to be unique?
You should _not_ assume that one end of a UUID value generated by CF will be unique.
I came across this little oddity at my last job, so this info is all pre CFMX (CF 5).
If you make a series of UUID value on a windows box, and another set on a Solaris box (with the exact same cf code), the first dozen or so characters will be changing while the last characters will remain relatively static in only one of the 2 series, and in the other series the first half of the characters will be static and the last half of the characters will be changing. I can't recall which OS was which way, but I do know they were the opposite of each other.
This may have all changed in the change to MX, but I'm not in a position to try it out anymore.
The lesson from this, don't assume a truncated portion of a UUID will be unique.
Regards
Darren Tracey
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