[Tfug] RDBMS reprise

[Bexley Hall]

Hi, Tim,

--- Tim Ottinger <tottinge at gmail.com> wrote:

> Bexley Hall wrote:
> > Recall I am trying to work with a (severely)
> > resource-starved client and databases of
> > potentially large size.  The problem is
> > handling queries which may return a large
> > number of results.
>   
> Okay... I need a little more.  How badly do you need
> the whole set?  Can 
> you select a more narrow set (like for list boxes
> and the like) and then 
> get the wider set only after a user selection is
> made? Do you have to 
> have a long, wide data set?  Can you afford
> round-trips to the server?  
> Does the client have local storage?  Can you use
> version control to 
> manage concurrency? Do you hold a transaction open
> on the server during 
> this operation?

I don't see any way to *avoid* making two (or more)
passes at the server to get all the data that an
application may need (e.g., the PDA example I
sited is a great model for thinking about the
sorts of issues that can arise... "How large of
an address book do you expect the user to have?
How many fields in each 'contact'?"  etc.)

I am trying hard not to tie up the server in
any way -- just hit it for a query and then
get out of the way.  As I said, there is no
bound on how long the *user* might opt to
wait between (related) queries.

Currently, I qualify each successive query with
those from which it was (obviously) derived so
that I can tell if a record has "disappeared",
etc.  I can see no way around this possibility
short of explicit locking *or* implicit locking
(even client-side locking!)

Datasets vary.  Some may be wide, others narrow.
E.g., consider the smarts that you might add to
fetch the area code for a particular address
based on its ZIP code (I, for one, don't enter
area codes in my address book so if I ever
forgot Tucson's -- for example -- I would have
to make this extra step manually).

--don



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