>Peter Epstein wrote in message <11082@palm-dev-forum>...
>
>Eric Sun wrote:
>>My question is, are these database sizes normal (i.e. are other people
>>programming with such large databases?). I ask this because I am having
>>some trouble with going through each record for the first 500 records and
>>then taking the foreign key to match a record in the second database.
This
>>is taking about 15-20 minutes to go through it all. Is it because of the
>>database sizes or because of my limited knowledge with database and the
>>searching capability that Palm comes with?
>
>When you say "taking the foreign key", are you referring to a record unique
ID or record >number (index) or something else? Finding a record given its
unique ID requires a linear >scan. That means that the operation you're
describing is going to get very slow: O(n >squared). If, on the other hand,
you used record numbers to get from one database to the >other, then each
access is nearly constant time. Of course, if you reference records by their
>index, you'll need to update the references whenever you insert a new
record, and that might >be too slow, depending on the sort order of the
database and the frequency of insertions. >You might want to use a cache
approach where each record in the first database refers to >records in the
second database using both a unique ID _and_ a record number. You try the
>record number first, and if it has the right unique ID, you're done. If
not, you find the record by >unique ID and update the record number. Again,
this will only be efficient if insertions are >rare. It isn't easy to come
up with a design that works well with lots of data. Hopefully some of >these
ideas can help you come up with a more efficient design for your problem.
>
Another approach is to store all your records strictly in the order entered,
but
have an indexing database that can be sorted and searched more quickly.
--
-Richard M. Hartman
[EMAIL PROTECTED]
186,000 mi/sec: not just a good idea, it's the LAW!
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