[elephant-devel] Querying Advice

[Daniel Salama]

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