Function EVL_field

src/jrd/evl.cpp:379–464

bool EVL_field(jrd_rel* relation, Record* record, USHORT id, dsc* desc)
{
/**************************************
 *
 *      E V L _ f i e l d
 *
 **************************************
 *
 * Functional description
 *      Evaluate a field by filling out a descriptor.
 *
 **************************************/

	DEV_BLKCHK(record, type_rec);

	if (!record)
	{
		// ASF: Usage of ERR_warning with Arg::Gds (instead of Arg::Warning) is correct here.
		// Maybe not all code paths are prepared for throwing an exception here,
		// but it will leave the engine as an error (when testing for req_warning).
		ERR_warning(Arg::Gds(isc_no_cur_rec));
		return false;
	}

	const Format* format = record->getFormat();
	fb_assert(format);

	if (id < format->fmt_count)
		*desc = format->fmt_desc[id];

	if (id >= format->fmt_count || desc->isUnknown())
	{
		// Map a non-existent field to a default value, if available.
		// This enables automatic format upgrade for data rows.
		// Reference: Bug 10424, 10116

		if (relation)
		{
			thread_db* tdbb = JRD_get_thread_data();

			const Format* const currentFormat = MET_current(tdbb, relation);

			while (id >= format->fmt_defaults.getCount() ||
				 format->fmt_defaults[id].vlu_desc.isUnknown())
			{
				if (format->fmt_version >= currentFormat->fmt_version)
				{
					format = NULL;
					break;
				}

				format = MET_format(tdbb, relation, format->fmt_version + 1);
				fb_assert(format);
			}

			if (format)
			{
				*desc = format->fmt_defaults[id].vlu_desc;