you image, once you have been pointed in the right direction. Take my advice with
a grain of salt.
First of all, ask yourself, what is the size of your dataset? Can you fit it all into memory?
If so, you have the full power of lisp at your command in dealing with the querying. You
will not have to write any macros to do this. You might find the DCM package, in the "contrib"
directory, a useful package, although it does not address querying; it is more of a cache handling
issue. (DCM has only been tested under SBCL, as far as I know.)
Under SBCL, when it comes to sorting you have "sort" and "stable-sort"; I think these are build in.
I'll eat a candle if you don't find them to blazingly fast (although the predicates that you pass them
might take some time.)
I think really the only good way to answer this question in a deeper way is to provide some
example code. I do exactly what you are talking about in my application (http://konsenti.com),
(although I use DCM), so I ought to be able to produce an example program relatively quickly.
You'll have to figure out how to map the GUI into those requests yourself, however.
I'll try to post an example by Monday.
On Sun, 2006-11-12 at 10:28 -0500, Daniel Salama wrote:
Hi all,
Coming from a Rails/MySQL world, we are having some difficulty trying
to comprehend/model/implement querying the database using dynamically
generated criteria.
For example, in the life we are trying to leave, we present the user
with advanced search screen, where they can select anywhere between 0
and 20 different search fields. When the user submits the screen, we
dynamically construct the WHERE SQL statement based on whatever
fields and information the user entered.
Obviously, I could envision this being the easy part, however, any
pointers would really help here. Then we rely on the SQL-engine to
perform the proper computations in order to return to us the matching
resultset.
In addition, the user is then able to dynamically sort the results to
their heart's desire. We simply dynamically generate the ORDER BY
clause as well.
As a learning task, we are trying to migrate some of this
functionality to Elephant using BDB. After reading the HTML-ized
tutorial and looking at some of the tests in the package, we still
have a hard time understanding how to go about implementing something
like this. From previous posts, we can use a cursor to jump into a
subset of the data we need to get (e.g. based on some indexed or
secondary indexed value in the search criteria). However, after that,
I guess we would have to sequentially navigate thru the results in
order to "manually" select each record based on all the other
possible search arguments. I suppose, in a way, this can be done
relatively painless by using macros (but we first would like to do
the manual expansion to learn how it would look like). Any ideas or
suggestions would certainly be appreciated here.
Then we have the issue of the sorting. I suppose it falls into a
similar situation: once we get the matching resultset from the
previous step, we would have to perform some "efficient" sort
algorithm on the data set dynamically based on the user's sorting
desire. I also suppose we could create a macro for this as well.
In a way, and after reading many posts out there, we are basically
wanting to bypass all the RDBMS machinery and working directly with
the data. After all, I guess many if not all of these RDBMS systems
are simply a SQL-domain language interface performing all these
computations and abstracting the direct access to the raw data, which
is probably even using BDB in the backend. So, I suppose we have to
learn to be able to roll-up our sleeves and deal with manipulating
the data in a more direct way.
Again, any ideas or suggestions here would be really appreciated.
Thanks,
Daniel
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