CREATE AGGREGATE FUNCTION
Adds a user-defined aggregate function (UDAF) stored in a shared Linux library to the catalog. You must have already loaded this library using the CREATE LIBRARY statement. When you call the SQL function, Vertica passes data values to the code in the library to process it.
CREATE AGGREGATE FUNCTION automatically determines the parameters and return value for the function from data supplied by the factory class.
Vertica supports overloading aggregate functions.
Syntax
CREATE [ OR REPLACE ] AGGREGATE FUNCTION [[database.]schema.]function ... AS [LANGUAGE 'language'] NAME 'factory' LIBRARY library;
Parameters
OR REPLACE
|
If you do not supply this parameter, |
[database.]schema
|
Specifies a schema, by default myschema.thisDbObject If you specify a database, it must be the current database. |
function |
Identifies the function to create, where function conforms to conventions described in Identifiers. This name does not need to match the name of the factory, but it is less confusing if they are the same or similar. |
LANGUAGE 'language'
|
The language used to develop this function, currently Default value: C++ |
NAME 'factory'
|
The name of the factory class in the shared library that generates the object to handle the function's processing. |
LIBRARY library
|
The name of the shared library that contains the C++ object to perform the processing for this function. This library must have been previously loaded using the CREATE LIBRARY statement. |
Privileges
Non-superuser:
- CREATE privilege on the function's schema
- USAGE privilege on the function's library
Examples
The following example demonstrates loading a library named AggregateFunctions then defining a function named ag_avg and ag_cat that are mapped to the ag_cat AverageFactory and ConcatenateFactory classes in the library:
=> CREATE LIBRARY AggregateFunctions AS '/opt/vertica/sdk/examples/build/AggregateFunctions.so'; CREATE LIBRARY => CREATE AGGREGATE FUNCTION ag_avg AS LANGUAGE 'C++' NAME 'AverageFactory' library AggregateFunctions; CREATE AGGREGATE FUNCTION => CREATE AGGREGATE FUNCTION ag_cat AS LANGUAGE 'C++' NAME 'ConcatenateFactory' library AggregateFunctions; CREATE AGGREGATE FUNCTION => \x Expanded display is on. select * from user_functions; -[ RECORD 1 ]----------+------------------------------------------------------------------ schema_name | public function_name | ag_avg procedure_type | User Defined Aggregate function_return_type | Numeric function_argument_type | Numeric function_definition | Class 'AverageFactory' in Library 'public.AggregateFunctions' volatility | is_strict | f is_fenced | f comment | -[ RECORD 2 ]----------+------------------------------------------------------------------ schema_name | public function_name | ag_cat procedure_type | User Defined Aggregate function_return_type | Varchar function_argument_type | Varchar function_definition | Class 'ConcatenateFactory' in Library 'public.AggregateFunctions' volatility | is_strict | f is_fenced | f comment |