[ http://issues.apache.org/jira/browse/DERBY-738?page=all ]
Daniel John Debrunner resolved DERBY-738:
-----------------------------------------
Fix Version: 10.2.0.0
Resolution: Fixed
Svn Revision: 354142
> Initialize parameters within activation without using generated code.
> ---------------------------------------------------------------------
>
> Key: DERBY-738
> URL: http://issues.apache.org/jira/browse/DERBY-738
> Project: Derby
> Type: Sub-task
> Components: SQL
> Reporter: Daniel John Debrunner
> Assignee: Daniel John Debrunner
> Priority: Minor
> Fix For: 10.2.0.0
>
> For each parameter in a query the following code is generated, e.g. for the
> 23rd parameter INT parameter.
> this.pvs.setStorableDataValue(
> this.getDataValueFactory().getNullInteger(),
> 22, // parameter number
> 4, // Types.INTEGER
> "java.lang.Integer");
> Apart being a significant amount of code per parameter , each of these will
> result in a new class pool entry for:
> - each parameter number (beyond 5)
> - each unique Types.XXX value (beyond 5)
> - each unique class name for a type
> (integer constants -1 through 5 are special cased as instructions in the JVM
> bytecode and do not require constant pool entries)
> This code is generated in the post constructor method of the generated class
> and its purpose is to allocate a holder DataValueDescriptor of the correct
> type to the ParameterValueSet for the statement. These are the parameters
> that will be directly set by the JDBC application.
> This code is generated by the method ParameterNode.generateHolder();
> The actual instanceof the ParameterValueSet is generated with a single call,
> by the generated code passing in the number of parameters to
> BaseActivation.setParameterValueSet. This then generates the structure for
> the parameters but does not create the DataValueDescriptors since the types
> are not known.
> The fix is to use the type definitions stored in the associated language
> PreparedStatement (prepared plan) DataTypeDescriptor[] to generate the null
> values and initalize the parameters.
> I'm looking at replacing the ParameterValueSet.setStorableDataValue with an
> initialize method like:
> public void initialize(DataTypeDescriptor[] types)
> {
> for (int i = 0; i < parms.length; i++)
> {
> DataTypeDescriptor dtd = types[i];
>
> parms[i].initialize(dtd.getNull(),
> dtd.getJDBCTypeId(),
>
> dtd.getTypeId().getCorrespondingJavaTypeName());
> }
> }
> With this, no code is required in the postConstructor() for a parameter. The
> initialize method is called when
> the activation is linked to its prepared statement.. With my prototype the
> generated code size for the DERBY-732 query dropped from around 70k to 60k.
> Of course this does not fix DERBY-732, since it is not reducing code in the
> where clause method.
>
>
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