Thanks for continuing the discussion, Bryan. Some more comments inline...
On 12/10/10 8:27 PM, Bryan Pendleton wrote:
These wrapper functions let you use SQL to examine
database, ResultSet, and parameter metadata.
The database metadata table function seems quite natural and powerful.
I'm less clear on how to use the RS and Parameter functions; I looked
at the examples in DERBY-4926 and DERBY-4927 but they seemed pretty
artificial. Do you have more substantial examples? Also, would these
latter two functions be useful in a JDBC program? Or are they something
that would mostly be useful in IJ?
Agreed, it's harder to come up with use-cases for the RS and PMD
examples. I have found them useful for using ij to measure a database's
JDBC compliance. These functions don't add much value to a Java program.
We could leave them out.
I guess what I'm asking is: could I somehow pass an actual ResultSet
object or PreparedStatement object to one of these functions? Or do
they always have to take a query string and compile it themselves?
They take a query string.
Lastly, why does it take several seconds to register these functions?
Is it due to how they are packaged? (That is, if they were embedded
in derby.jar would the registration go faster?) I'm a bit surprised
that something as seemingly trivial as registering three table
functions could take that much time.
Right. Sorry for not explaining this in greater depth. A wrapper
function is registered for each method in DatabaseMetaData. So that's
about 170 functions which have to be registered. I think that if they
were directly registered by DataDictionaryImpl, it would be faster--that
would just involve stuffing 170 rows into a catalog. What I was
measuring was registration via a series of compiled CREATE FUNCTION
statements. There's some compiler overhead here.
Thanks,
-Rick
Anyway, thanks very much for doing this work, and for advancing the
proposal; it's quite interesting and I've been learning a lot by
reading your work and following the discussions!
bryan
