Method generateSort

src/jrd/optimizer/Optimizer.cpp:1442–1746

//

SortedStream* Optimizer::generateSort(const StreamList& streams,
									  const StreamList* dbkeyStreams,
									  RecordSource* rsb,
									  SortNode* sort,
									  bool refetchFlag,
									  bool projectFlag)
{
	/* We already know the number of keys, but we also need to compute the
	total number of fields, keys and non-keys, to be pumped thru sort.  Starting
	with the number of keys, count the other field referenced.  Since a field
	is often a key, check for overlap to keep the length of the sort record
	down. */

	/* Along with the record number, the transaction id of the
	 * record will also be stored in the sort file.  This will
	 * be used to detect update conflict in read committed
	 * transactions. */

	ULONG items = sort->expressions.getCount() +
		3 * streams.getCount() + 2 * (dbkeyStreams ? dbkeyStreams->getCount() : 0);
	const NestConst<ValueExprNode>* const end_node = sort->expressions.end();

	// Collect all fields involved into the sort

	HalfStaticArray<SortField, OPT_STATIC_ITEMS> fields;
	ULONG totalLength = 0;

	for (const auto stream : streams)
	{
		UInt32Bitmap::Accessor accessor(csb->csb_rpt[stream].csb_fields);

		if (accessor.getFirst())
		{
			do
			{
				const auto id = accessor.current();

				const auto format = CMP_format(tdbb, csb, stream);
				const auto desc = &format->fmt_desc[id];

				if (id >= format->fmt_count || desc->isUnknown())
					IBERROR(157);		// msg 157 cannot sort on a field that does not exist

				fields.push(SortField(stream, id, desc));
				totalLength += desc->dsc_length;

				// If the field has already been mentioned as a sort key, don't bother to repeat it.
				// Unless this key is computed/volatile and thus cannot be restored after sorting.

				for (const auto expr : sort->expressions)
				{
					const auto fieldNode = nodeAs<FieldNode>(expr);

					if (fieldNode && fieldNode->fieldStream == stream && fieldNode->fieldId == id)
					{
						if (!SortedStream::hasVolatileKey(desc))
						{
							totalLength -= desc->dsc_length;