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Creating Special-Purpose UDRs

In This Chapter

Writing an End-User Routine

Writing a Cast Function

Writing an Iterator Function

Initializing the Iterations

Returning One Active-Set Item

Releasing Iteration Resources

Calling an Iterator Function from an SQL Statement

Registering the Iterator Function

Executing the Iterator Function

Writing an Aggregate Function

Extending a Built-In Aggregate

Choosing the Operator Function

Writing the Operator Function

Registering the Overloaded Operator Function

Using the Extended Aggregate

Creating a User-Defined Aggregate

Determining the Aggregate State

Writing the Aggregate Support Functions

Defining the User-Defined Aggregate

Using the User-Defined Aggregate

Determining Required Aggregate Support Functions

Sample User-Defined Aggregates

Providing UDR-Optimization Functions

Writing Selectivity and Cost Functions

Query Selectivity

MI_FUNCARG Data Type

Obtaining Information About Constant Arguments

Obtaining Information About Column Arguments

Creating Negator Functions

Creating Commutator Functions

Creating Parallelizable UDRs

Writing the Parallelizable UDR

Registering the Parallelizable UDR

Executing the Parallelizable UDR

Debugging the Parallelizable UDR

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