Paul
What I meant was that ISAMs encouraged Key->Prev/Next, PgUp/PgDn data
navigation, whereas
RDMS didn't work that well with this logic, better to use Key -> Subset
-> Select from list logic, which
fits with larger datasets, though you will occasionally see a recidivist
hammering the page down key as they
search for 1 item in 10,000 rather than type a few characters
Neven
Neven wrote:
I sometimes wonder if the problem is that developers start
with too small sets of test data and design their navigation
logic around that not realising of course in real life above
a 100 records or so the rules change
Hrmm.. I don't think it's really a data size or data structure thing. We
have clients with 30Gb+ Accredo databases and lotsa users and it perform
well for them. Large data volumes need thought (and appropriate index
use!) whether it's navigational or relationally accessed.
After all, relational is something you generally layer on top of a lower
level navigational tuple store anyway - that's how most major relational
engines work, starting from the original System-R from IBM.
If you look at the history of the relational model, the advantage was
declarative vs procedural query specification which which was driven by
the need for easier ad-hoc reporting and accellerated by the fact that
it gets tricky in large complex databases for _developers_ to figure out
_how_ to choose (and successfully code!) a good access plan given the
varying data distribution and available access options (indexes, join
orders, etc.)
That's what SQL execution engines _do_ at their core - query optimise
(hard) and then execute (easy). Many cheaper ones do this quite poorly
as query optimisation is hard to do well. As our developer, Steve knows
- since he got to write a (pretty?) good one (well, much better than
DBISAM) at my insistence :-)
One thing I hated about ADO was its insistence on concurrency
control, I design my dbs so concurrency is not required but
it insisted on it, which was also a legacy of 'client side'
business logic (ie VB/Access apps), it was I must say a step
up from the BDE 'Primary Key? what's a Primary Key?' approach
Maybe we should start a list -- 10 no a 100 things i hated
about the BDE
Well, I'm sure the others on the list are starting to feel like they've
had to wade through that already with me opining away. So I'll shut up
now unless anyone actually asks more questions :-)
TTFN,
Paul.
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