Consume Table Data Using a Row Block

The TPF consumes table data using the fetch_into or fetch_block row block structures.

Each successful call to either fetch_into or fetch_block populates a a_v4_extfn_row_block structure.

The a_v4_extfn_row_block members are:

max_rows – the number of table rows the row block can store in a piece of memory.
num_rows – the number of rows actually produced or available for consumption. Cannot be larger than max_rows.
row_data – the array of rows produced or available for consumption. Each row is an a_v4_extfn_row structure.

Each row of table data in row_data has these members:

row_stats – indicates whether values for this row are present. A value of 1 means the values are present; 0 means the values are not.
column_data – the column data associated with this row.

The column_data members are:

Member	Description
`null_value`	The value representing NULL
`null_mask`	One or more bits used to represent the NULL value
`data`	Pointer to the data for the column. Depending on the type of fetch mechanism, either points to an address in the consumer, or an address where the data is stored in the UDF.
`piece_len`	The actual length of data for variable-length data types
`blob`	A non-NULL value means that the data for this column must be read using the blob API