Function BTR_description

src/jrd/btr.cpp:948–1048

bool BTR_description(thread_db* tdbb, jrd_rel* relation, index_root_page* root, index_desc* idx,
					 USHORT id)
{
/**************************************
 *
 *	B T R _ d e s c r i p t i o n
 *
 **************************************
 *
 * Functional description
 *	See if index exists, and if so, pick up its description.
 *  Index id's must fit in a short - formerly a UCHAR.
 *
 **************************************/
	SET_TDBB(tdbb);

	if (id >= root->irt_count)
		return false;

	const index_root_page::irt_repeat* irt_desc = &root->irt_rpt[id];

	if (irt_desc->getRoot() == 0)
		return false;

	idx->idx_id = id;
	idx->idx_root = irt_desc->getRoot();
	idx->idx_count = irt_desc->irt_keys;
	idx->idx_flags = irt_desc->irt_flags;
	idx->idx_runtime_flags = 0;
	idx->idx_foreign_primaries = nullptr;
	idx->idx_foreign_relations = nullptr;
	idx->idx_foreign_indexes = nullptr;
	idx->idx_primary_relation = 0;
	idx->idx_primary_index = 0;
	idx->idx_expression = nullptr;
	idx->idx_expression_statement = nullptr;
	idx->idx_condition = nullptr;
	idx->idx_condition_statement = nullptr;
	idx->idx_fraction = 1.0;

	// pick up field ids and type descriptions for each of the fields
	const UCHAR* ptr = (UCHAR*) root + irt_desc->irt_desc;
	index_desc::idx_repeat* idx_desc = idx->idx_rpt;
	for (int i = 0; i < idx->idx_count; i++, idx_desc++)
	{
		const irtd* key_descriptor = (irtd*) ptr;
		idx_desc->idx_field = key_descriptor->irtd_field;
		idx_desc->idx_itype = key_descriptor->irtd_itype;
		idx_desc->idx_selectivity = key_descriptor->irtd_selectivity;
		ptr += sizeof(irtd);
	}
	idx->idx_selectivity = idx->idx_rpt[idx->idx_count - 1].idx_selectivity;

	ISC_STATUS error = 0;
	if (idx->idx_flags & idx_expression)
	{
		MET_lookup_index_expression(tdbb, relation, idx);