Re: [Firebird-devel] User semantics vs authentication

[Jim S. <ja...@ne...>]

Aleksey Karyakin wrote:

>>This question has been around longer than Interbase.  The great unwritten 
>>component is traditionally called the mega-database manager.
>>    
>>
>
>Why unwritten ? I thought there are lots of Mega Database Managers on the 
>market. Most "big" DBMS have such capability not counting separate products.
>
>  
>
It just never made it to the top of the list.  A client willing to pay 
for it would have moved it up, but the client has never stepped 
forward.  Even Sean has declined to pay for it.

>What's the difference between performing a join (for example) using two 
>tables in the single database or from the separate database files on the 
>same Firebird server ? Two tables are just objects loaded in server memory 
>at some point.
>  
>
It's not nearly that simple.  The table itself is materialized record by 
record, never as a single entity.  What version of a record is 
appropriate for a particular transaction, the exact format of the 
record, whether garbage collection needs to be performed are all driven 
by relatively complex, interlocked data structures that drive a database 
engine.   The data structures, in turn, are isolated from each other by 
the V-valve.  Extending the engine to allow cross talk across two or 
more physical databases would required a total resign of the system.  
And while it well might benefit from a ground up redesign, it probably 
wouldn't be Firebird compatible when it was finished.  For example, if 
you were going to start over, why keep BLR?  But if you don't keep BLR, 
you've cut yourself off from the entire installed base.

A better solution is to layer a solution on existing engines.  The MDM 
would be a provider using the same API as the engine, the remote 
interface, and the gateway.  It would prepare DSQL statements by 
decomposing it into SQL statements for execution on that target bases, 
calling back into the Y-valve for access, and coordinating the results.  
The implementation would be smaller and simpler than the changes 
required to do the same thing in the engine, and would automatically 
work for remote databases, engines of different version, and the gateway 
to Interbase and legacy Firebird.

-- 

Jim Starkey
Netfrastructure, Inc.
978 526-1376