Function BsonOrderbyCore

pg_documentdb/src/query/bson_dollar_operators.c:2862–2924

* Helper for BsonOrderBy that accepts a options to strictly check the types of documents involved * in the ordering. * Few cases require the type to be same e.g. $sort in `$setWindowFields` stage */

 * Few cases require the type to be same e.g. $sort in `$setWindowFields` stage
 */
static Datum
BsonOrderbyCore(pgbson *document, pgbson *filter, const char *collationString,
				bool validateSort, CustomOrderByOptions options)
{
	bson_iter_t documentIterator;
	pgbsonelement filterElement;
	TraverseOrderByValidateState state = {
		{ 0 }, NULL, { 0 }, options, collationString, 0, false
	};

	pgbson_writer writer;
	PgbsonInitIterator(document, &documentIterator);
	PgbsonToSinglePgbsonElement(filter, &filterElement);
	uint32_t filterPathLength = filterElement.pathLength;
	filterElement.pathLength = 0;

	if (TryCheckMetaScoreOrderBy(&filterElement.bsonValue))
	{
		PgbsonWriterInit(&writer);
		double ranking = EvaluateMetaTextScore(document);
		PgbsonWriterAppendDouble(&writer, "rank", 4, ranking);
		PG_RETURN_POINTER(PgbsonWriterGetPgbson(&writer));
	}

	if (!BsonValueIsNumber(&filterElement.bsonValue) && validateSort)
	{
		ereport(ERROR, (errcode(ERRCODE_DOCUMENTDB_BADVALUE),
						errmsg("Sort direction value %s is not valid",
							   BsonValueToJsonForLogging(
								   &filterElement.bsonValue))));
	}

	int32_t orderBy = BsonValueAsInt32(&filterElement.bsonValue);
	state.isOrderByMin = orderBy == 1;

	TraverseBson(&documentIterator, filterElement.path, &state.traverseState,
				 &OrderByExecutionFuncs);

	/* Match order by outputs similar to what the index produces for terms */
	PgbsonWriterInit(&writer);
	if (state.orderByValue.value_type == BSON_TYPE_EOD)
	{
		/* here we write an empty path and minKey so it's sorted first. */
		state.orderByValue.value_type = BSON_TYPE_UNDEFINED;
	}

	PgbsonWriterAppendValue(&writer, filterElement.path, filterPathLength,
							&state.orderByValue);

	/* append the collation for use in bson_orderby_compare */
	if (IsCollationApplicable(collationString))
	{
		PgbsonWriterAppendUtf8(&writer, "collation", 9, collationString);
	}

	if (options == CustomOrderByOptions_SetReverseFlag)
	{
		/* if the order by is min, we set the reverse flag to true */