OpenEuphoria

Re: Berkeley DB with Euphoria

• Posted by Robert Craig <rds at RapidEuphoria.com> Sep 30, 2002
• 452 views

Rudy Toews writes:
> ...could something similar be a feature of EDS? having the 
> different open databases /selected tables use their own 
> 'buffers' without explict 'selecting' them?
> i am currently building 1 database and many tables 
> but would like to break it up somewhat. and still move data 
> between them easier.

At the very outset, in designing EDS, I had a choice
of:
    1. have the user specify the database & table 
        on each operation, 
or:
    2. have a "context" where the database and
        table were established beforehand, and all database
       operations would have shorter parameter lists.

I went with #2. I don't regret it, but there are situations
where it is inconvenient. 

When you select a table, EDS reads in 4 bytes per record
in that table. This is inefficient when you have a lot of records
(over 1000 say) and you are trying to rapidly flip back and forth 
between tables. Obviously some buffering would help,
i.e. keep the record pointers in memory. Maybe I'll do something
about this. Note that it's dangerous to modify part of the data base
structure in memory only, in case your program crashes 
and the database on disk is left in an inconsistent (corrupted) state.
Simply keeping a copy of the record pointers in memory 
should be safe as long as other processes are locked out from
making changes. There's also the issue of how much memory
this might require. If you have lots of tables with lots of records
you might run out of memory. 

If you look at db_compress() you'll see that it copies records,
between tables, 20 at a time. That's another approach 
to the problem.

Regards,
   Rob Craig
   Rapid Deployment Software
   http://www.RapidEuphoria.com