Method compose

src/jrd/btr.cpp:538–706

// IndexKey class

idx_e IndexKey::compose(Record* record)
{
	// Compute a key from a record and an index descriptor.
	// Note that compound keys are expanded by 25%.
	// If this changes, both BTR_key_length and GDEF exe.e have to change.

	const auto dbb = m_tdbb->getDatabase();
	const auto maxKeyLength = dbb->getMaxIndexKeyLength();

	temporary_key temp;
	temp.key_flags = 0;
	temp.key_length = 0;

	dsc desc;
	dsc* desc_ptr;

	auto tail = m_index->idx_rpt;
	m_key.key_flags = 0;
	m_key.key_nulls = 0;

	const bool descending = (m_index->idx_flags & idx_descending);

	try
	{
		if (m_index->idx_count == 1)
		{
			// For expression indices, compute the value of the expression

			if (m_index->idx_flags & idx_expression)
			{
				if (!m_expression)
					m_expression = FB_NEW_POOL(*m_tdbb->getDefaultPool()) IndexExpression(m_tdbb, m_index);

				desc_ptr = m_expression->evaluate(record);
				// Multi-byte text descriptor is returned already adjusted.
			}
			else
			{
				// In order to "map a null to a default" value (in EVL_field()),
				// the relation block is referenced.
				// Reference: Bug 10116, 10424

				if (EVL_field(m_relation, record, tail->idx_field, &desc))
				{
					desc_ptr = &desc;

					if (desc_ptr->dsc_dtype == dtype_text &&
						tail->idx_field < record->getFormat()->fmt_desc.getCount())
					{
						// That's necessary for NO-PAD collations.
						INTL_adjust_text_descriptor(m_tdbb, desc_ptr);
					}
				}
				else
				{
					desc_ptr = nullptr;
				}
			}