The TPF fetches table data from an input table using an open result set.
Fetching is accomplished by calling either fetch_block or fetch_into on the a_v4_extfn_table_context object returned from open_result_set. The TPF can choose which fetch method to use. If fetch_block is used, the server is responsible for rowblock allocation. If fetch_into is used, the TPF is responsible for row block allocation.
Each call to the fetch method returns either nothing, which is indicated by a return value of false, or returns a populated row block structure. The row block structure can then be used to consume the table data.