Question

I have a query like this:

select samplePackage.prepareMessage(t.message) as text 
from 
sampleSchema.sampleTable t;

sampleTable has large data (number of rows 30M)
prepareMessage is a java stored procedure.

private static String prepareMessage(String message) {
   //do some things...
   return preparedMessage;
}

I’m trying to execute this query in parallel. How can i do it?

Thanks.

Answer 1

I’ve never tried it with Java function myself. But the approach should be as followos:

Run your query with the PARALLEL hint:

select /*+ PARALLEL(t) */ samplePackage.prepareMessage(t.message) as text 
from sampleSchema.sampleTable t;

To successfully execute the SELECT in parallel, Oracle needs to know that your Java function is safe for that. So you have to declare it either as PARALLEL_ENABLE or provide RESTRICT_REFERENCES.

CREATE OR REPLACE FUNCTION PREPARE_MESSAGE(message IN VARCHAR2) RETURN VARCHAR2 PARALLEL_ENABLE
AS LANGUAGE JAVA
    NAME 'sampleSchema.samplePackage.prepareMessage(Java.lang.String) return Java.lang.String';

The query then becomes:

select /*+ PARALLEL(t) */ PREPARE_MESSAGE(t.message) as text 
from sampleSchema.sampleTable t;

There are further restrictions that apply to the function, e.g. it may not execute DML statements. Otherwise, a parallel execution isn’t possible.

As I said: I haven’t tried it with Java. But that’s the direction to go.

Update: I’ve changed the code from using a package to using a function. It should be simpler like this.