EXTFNAPIV4_DESCRIBE_COL_VALUES_SUBSET_OF_INPUT (Set)

Data Type

a_v4_extfn_col_subset_of_input

Description

Column values are a subset of the values specified in an input column.

Usage

Setting this describe attribute informs the query optimizer that the indicated column values are a subset of those values specified in an input column. For example, consider a filter TPF that consumes a table and filters out rows based on a function. In such a case, the return table is a subset of the input table. Setting EXTFNAPIV4_DESCRIBE_COL_VALUES_SUBSET_OF_INPUT for the filter TPF optimizes the query.

Returns

On success, returns the sizeof(a_v4_extfn_col_subset_of_input).

On failure, returns one of the generic describe_column errors, or:

• EXTFNAPIV4_DESCRIBE_BUFFER_SIZE_MISMATCH – set error returned if the buffer length is less than sizeof (a_v4_extfn_col_subset_of_input).
• EXTFNAPIV4_DESCRIBE_INVALID_ATTRIBUTE_VALUE – set error returned if the column index of the source table is out of range.
• EXTFNAPIV4_DESCRIBE_NOT_AVAILABLE – set error returned if the column subset_of_input is set on is not aplicable (for example, if the column is not in the select list).
• EXTFNAPIV4_DESCRIBE_INVAILD_STATE – set error returned if the query processing state is not Optimization.
• EXTFNAPIV4_DESCRIBE_BUFFER_SIZE_MISMATCH – set error returned if the buffer length is zero.
• EXTFNAPIV4_DESCRIBE_INVALID_PARAMETER – set error returned if called on a parameter other than the return table.

Query Processing States

Valid in:

• Optimization state

Example

a_v4_extfn_col_subset_of_input colMap;

	colMap.source_table_parameter_arg_num = 4;
	colMap.source_column_number = i;

	desc_rc = ctx->describe_column_set( ctx, 
		0, i, 
		EXTFNAPIV4_DESCRIBE_COL_VALUES_SUBSET_OF_INPUT, 
		&colMap, sizeof(a_v4_extfn_col_subset_of_input) );