Contract Function | Table Operators | Teradata Vantage - Contract Function - Advanced SQL Engine - Teradata Database

You can write a user-defined contract function which determines the output table row format of your table operator. The contract function is invoked at runtime when the table operator is being parsed.

The contract function is similar to a standard scalar UDF. The function takes no input parameters and returns an integer SUCCESS or FAILURE value.

The contract function can access table operator input information using FNC functions and set the return row format using an FNC function. The contract function context is accessible by the table operator.

For details about the FNC functions that the contract function can use, see Table Operator Interface.

You associate a contract function with a table operator by using the RETURNS TABLE clause of the CREATE FUNCTION statement.

For example, if you have a table operator defined as:

void udaggregation ()
{
     ...
}

And you have a contract function defined as:

void udaggregation_contract (
   INTEGER *result,
   int *indicator_Result,
   char sqlstate[6],
   SQL_TEXT extname[129],
   SQL_TEXT specific_name[129],
   SQL_TEXT error_message[257])
{
     ...
}

Then you associate the contract function with the table operator by specifying the name of the contract function in the RETURNS TABLE clause in the SQL definition of the table operator as follows:

REPLACE FUNCTION udaggregation ()
   RETURNS TABLE VARYING USING FUNCTION udaggregation_contract
   LANGUAGE C
   NO SQL
   PARAMETER STYLE SQLTABLE
   EXTERNAL NAME 'CS!udaggregation!udaggregation.c!F!udaggregation';

The maximum length of the contract function name is CHAR(30) CHARACTER SET LATIN. The CREATE FUNCTION statement fails if the contract function name exceeds this limit after the string is converted into LATIN for storage in the Data Dictionary.

Once created, you cannot drop a contract function directly. When the table operator is dropped, the contract function is also dropped. Similarly, you cannot alter a contract function directly. When the table operator is altered to run in a different mode, the contract function is also altered. When the table operator is recompiled, the contract function is also recompiled.

You cannot rename the table operator or the contract function.

For a C code example of a table operator and contract function, see C Table Operator.