If this is a duplicate, I apologize for the bandwidth.

For most transparent support, I represent them as text, CHAR (38) NOT NULL. Others prefer a binary representation. Since I spent 5 years in a rapid response team, three of those as the only 24x7 on call support for a key enterprise product, I am very much concerned about minimizing the support (my) workload, even if it consumes a bit more storage resources. At about 2 to 3 dollars a gigabyte, storage is cheap. If I can store it in a standard, recognizable text form, I will.

I am more concerned with transparency of the back end DBMS than with saving 20 bytes per record. If you are aiming at a palm system, then the concerns would be reversed.

A GUID is not a "sortable" field in the sense that order has any meaning, so it is not appropriate for every situation. However, it is guaranteed unique until the year 3040. So for distributed systems (which is what it was designed for) it is ideal as a primary key. A clustered index on a GUID would probably not provide any benefit.

GUID is generally generated by OS level calls (Windows or UNIX) or by one of about a hundred Java classes, depending on whose libraries you like to use.

My own WIP framework actually has a "master object table" that cross references known GUID's to the tables that they physically reside in and the class structures that instantiate them, allowing you to have nothing but the GUID and get to the data you need with two queries. From this, it is probably becoming apparent that the framework itself hides much of the DBMS overheads from the end user, so speed and efficiency are important to me but only within the context that it does not reduce supportability.

My testing has established that a GUID represented as CHAR(38) NOT NULL averages about 3 I/O (30 ms) per lookup on a table with 4,000,000 rows.

For the GUID discussion, this snip contains all you need as an example of how I use them. A "Memento" is a pattern also called a "Value Object", that has only values - for our purposes the memento fields correspond to table columns in the design.

Code snip ...

{**
* @created 2004-01-09-22.09.47.620
* @author RACE Code Generator (Auto-create) Version 0.0.0.0
*
* @todo Verify code for method SetParams
*
*}
procedure TContact_001_IBOPersistor.SetParamsWithName (_Memento: Tmemento; _params: TIB_Row);
var
E: Exception;
begin
if not (_Memento is TContact_001_Memento) then
begin
E := EInvalidCast.CreateFmt ('Memento %s cannot be saved as %s', [ _Memento.className, TContact_001_Memento.classname ]);
// Log.LogException (E, self, module_name, 'SetParams');
raise E;
end;

with _params, (_memento as TContact_001_Memento) do
begin
try
BeginUpdate;
try
ParamByName ('CREATE_STAMP_USER_OID').AsString := GUIDToString (FCreate_Stamp.User_OID);
ParamByName ('CREATE_STAMP_USER_SID').AsInteger := FCreate_Stamp.User_SID;
ParamByName ('CREATE_STAMP_INTER_OID').AsString := GUIDToString (FCreate_Stamp.Intermediary_OID);
ParamByName ('CREATE_STAMP_INTER_SID').AsInteger := FCreate_Stamp.Intermediary_SID;
// *** TimeStamp not supported by some libraries "as-shipped"
// ParamByName ('CREATE_STAMP_TIME').AsSQLTimeStamp := FCreate_Stamp.time;
ParamByName ('CREATE_STAMP_TIME').AsDateTime := SQLTimeStampToDateTime (FCreate_Stamp.time);
ParamByName ('CREATE_STAMP_METH').AsString := FCreate_Stamp.MethodName;
ParamByName ('CREATE_STAMP_PGM').AsString := FCreate_Stamp.Programname;

// ParamByName ('EFFECTIVE_TS').AsSQLTimeStamp := DateTimeToSQLTimeStamp (FEffective_TS);
ParamByName ('EFFECTIVE_TS').AsDateTime := FEffective_TS;
// ParamByName ('END_TS').AsSQLTimeStamp := DateTimeToSQLTimeStamp (FEnd_TS);
ParamByName ('END_TS').AsDateTime := FEnd_TS;
ParamByName ('OID').AsString := GUIDToString (FOID);
ParamByName ('SID').AsInteger := FSID;
ParamByName ('VOID_STAMP_USER_OID').AsString := GUIDToString (FVoid_Stamp.User_OID);
ParamByName ('VOID_STAMP_USER_SID').AsInteger := FVoid_Stamp.User_SID;
ParamByName ('VOID_STAMP_INTER_OID').AsString := GUIDToString (FVoid_Stamp.Intermediary_OID);
ParamByName ('VOID_STAMP_INTER_SID').AsInteger := FVoid_Stamp.Intermediary_SID;
// ParamByName ('VOID_STAMP_TIME').AsSQLTimeStamp := FVoid_Stamp.time;
ParamByName ('VOID_STAMP_TIME').AsDateTime := SQLTimeStampToDateTime (FVoid_Stamp.time);
ParamByName ('VOID_STAMP_METH').AsString := FVoid_Stamp.MethodName;
ParamByName ('VOID_STAMP_PGM').AsString := FVoid_Stamp.Programname;
ParamByName ('APARTMENT').AsString := FApartment;
ParamByName ('CITY').AsString := FCity;
ParamByName ('COUNTRY').AsString := FCountry;
ParamByName ('EMAIL').AsString := Femail;
ParamByName ('EMAIL_SERVER').AsString := Femail_server;
ParamByName ('FIRST_NAME').AsString := FFirst_Name;
ParamByName ('LAST_NAME').AsString := FLast_Name;
ParamByName ('POSTALCODE').AsString := FPostalCode;
ParamByName ('STREET').AsString := FStreet;
finally
EndUpdate (true);
end;
except
on E:Exception do begin
// Log.LogException (E, self, module_name, 'SetParams');
raise;
end;
end;
end;
end;

----- Original Message -----
From: akestion
To: firebird-support@yahoogroups.com
Sent: Wednesday, April 07, 2004 5:50 AM
Subject: [firebird-support] Who's using some GUID (Global Unique IDentifiers) in FB?


Hello,

Can you advise me about "Global Unique IDentifiers", which Udf to use
and is it really efficient ?
I want ot use it in order to do disconnected works with data and
after update database.
It would be nice if you have a little exemple.
Thanks you.



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