Scalar and Aggregate UDF Calling Patterns

Calling patterns are steps the functions perform as results are gathered.

• Scalar and Aggregate UDF Callback Functions
  The set of callback functions are supplied by the engine through the a_v3_extfn_scalar_context structure and used within the user's UDF functions.
• Scalar UDF Calling Pattern
  Expected calling pattern for supplied function pointers for a scalar UDF calling pattern.
• Aggregate UDF Calling Patterns
  The calling patterns for the user-supplied aggregate UDF functions are more complex and varied than the scalar calling patterns.