Jazarine Jamal wrote:
Really thanks for the reply...
Is it possible to get the LCC at some later point of execution : in
the JDBCDisplayUtil?
I have got the Connection object in the function that i need. I want
to if its possible to get the activation object related to the current
connection.
By the way, why is that getCurrentLCC() throws an error when used in
JDBCDisplayUtil but not when it is used in classes such as
ConsistencyChecker, etc..?
Hi Jazarine,
The LanguageConnectionContext is the root of the SQL interpreter's state
variable for a session. That is, the LCC is used to cache all sorts of
information needed to parse, optimize, and execute queries. The LCC is a
structure which only exists in the Derby engine layer, that is, it is
only visible to code that is running on the server side of a JDBC
connection.
JDBCDisplayUtil is tools code which runs outside the engine on the
client side of a JDBC connection. JDBCDisplayUtil can run across the
network in a remote client. In that remote layer, the LCC does not
exist. In contrast, ConsistencyChecker runs inside the engine.
Hope this helps,
-Rick
On Jan 20, 2008 6:07 PM, Thomas Nielsen < [EMAIL PROTECTED]
<mailto:[EMAIL PROTECTED]>> wrote:
Hi Jazarine,
I'm assuming you need to get the LCC once you are in the execute
phase,
and in a class implementing ResultSet. All the different ResultSet
implementations in org.apache.derby.impl.sql.execute get an
activation
supplied to their constructor either directly, or through its
source/child ResultSet. It should hence be available either:
- as a member of the given ResultSet class
- though the ResultSets source/child ResultSet
- through getLanguageConnectionContext()
- or through getActivation().getLanguageConnectionContext()
depending on the ResultSet class implementation you are in.
It could be beneficial to have a look around
ProjectRestrictNodeResultSet, the top-most ResultSet for a SELECT qry,
and see how it's fetched/used?
Activations are created/built with an ActivationClassBuilder and is
populated during the bytecode generation phase. You can see one
example
of how the ActivationClassBuilder is used in
ProjectRestrictNode.generateMinion() in
org.apache.derby.impl.sql.compile. ProjectRestrictNode is the node
generating the ProjectRestrictNodeResultSet (and a few others for the
sake of correctness).
Generally we push objects to the stack, then call to
ActivationClassBuilder to push generation of the correct type of
ResultSet on the stack. This is where the actual Activation object is
created, and as previously stated it's often pushed as a parameter to
the ResultSet constructor. Once code generation is completed, we start
executing the generated bytecode. Someone with a little more
knowledge
of the details may want to explain this further, or correct me, if
necessary? :)
Hope this helps you figure it out :)
Thomas
Jazarine Jamal wrote:
> I need to get the langaugeconnectioncontext.
> I presume it can be done through this:
>
>
LangaugeConnectionContext=activation.getLangaugeConnectionContext()
>
>
>
> But How do I create an Activation object? Are there any implemented
> classes for Activation interface..??
> I am doing this since it forms a part of the code to get the type of
> an object.
>
>
> Please get me some help as soon as possible..
