Hi Shazin,
Some responses inline...
Shazin Sadakath wrote:
Hi Rick,
Thanks for that very descriptive reply.
I have some more questions.
1. So what the Create Procedure/Function statement actually does is
creating an Alias to
a static java method??
That's right. So a Procedure/Function definition results in a row in
SYS.SYSALIASES. It also results in a couple rows in SYS.SYSCOLUMNS, one
for each parameter to the Procedure/Function.
2. When the Created Procedure/Function is called at the run time. How
does the loading and execution
take place?
In Derby, a prepared SQL statement is a generated Java class, which
Derby fills in and compiles. The invocation of the procedure/function is
just generated byte code for calling the static method that is bound to
the procedure/function. Derby class loading is a little tricky, but at a
high level classes can come from three places:
o From the VM classpath
o From jar files which have been stored in the database and wired into a
database-specific classpath
o From the cache of generated classes which are the executable forms of
SQL statements
I am going on vacation now so please don't be put off by my radio
silence. Hopefully, other developers in the community can answer
follow-on questions which you may have.
Cheers,
-Rick
Thanks,
Shazin
On Fri, Nov 20, 2009 at 7:34 PM, Rick Hillegas
<[email protected] <mailto:[email protected]>> wrote:
Shazin Sadakath wrote:
Hi All,
Can anyone guide me on what classes in the source are
associated with creating a DerbySQL Routine please???
Thanks,
Shazin
Hi Shazin,
The processing flow is something like this:
o The parser (sqlgrammar.jj) creates a CreateAliasNode to
represent the user's CREATE FUNCTION/PROCEDURE
o The rest of compilation for the CREATE FUNCTION/PROCEDURE
statement is handled by the bindStatement() and
makeConstantAction() methods of the CreateAliasNode.
o In particular, CreateAliasNode.makeConstantAction() creates the
execution-time object which does the heavy lifting: a
CreateAliasConstantAction object.
o At statement-execution time, the CreateAliasConstantAction
populates the data dictionary. That is the
CreateAliasConstantAction adds a persistent AliasDescriptor, which
describes the new function/procedure.
o The AliasDescriptor is stored in SYS.SYSALIASES. The really
interesting bits of the AliasDescriptor are the AliasInfo object
which it contains. That AliasInfo object is stored in the
ALIASINFO column of SYS.SYSALIASES.
Hope this helps,
-Rick
