Function ValidateMatchForOrderbyQuals

pg_documentdb/src/index_am/rum.c:948–1006

* ValidateMatchForOrderbyQuals walks the order by operator * clauses and ensures that every clause is valid for the * current index. */

 * current index.
 */
static bool
ValidateMatchForOrderbyQuals(IndexPath *path)
{
	ListCell *orderbyCell;
	int index = 0;
	foreach(orderbyCell, path->indexorderbys)
	{
		Expr *orderQual = (Expr *) lfirst(orderbyCell);

		/* Order by on RUM only supports OpExpr clauses */
		if (!IsA(orderQual, OpExpr))
		{
			return false;
		}

		/* Validate that it's a supported operator */
		OpExpr *opQual = (OpExpr *) orderQual;
		if (EnableOrderByIndexTerm &&
			opQual->opfuncid != BsonOrderByFunctionOid() &&
			opQual->opfuncid != BsonOrderByIndexFunctionOid() &&
			opQual->opfuncid != BsonOrderByIndexWithCollationFunctionOid() &&
			opQual->opfuncid != BsonOrderByIndexWithCollationReverseFunctionOid() &&
			opQual->opfuncid != BsonOrderByIndexReverseFunctionOid())
		{
			return false;
		}
		else if (opQual->opfuncid != BsonOrderByFunctionOid())
		{
			return false;
		}

		/* OpExpr for order by always has 2 args */
		Assert(list_length(opQual->args) == 2);
		Expr *secondArg = lsecond(opQual->args);
		if (!IsA(secondArg, Const))
		{
			return false;
		}

		Const *secondConst = (Const *) secondArg;
		int indexColInt = list_nth_int(path->indexorderbycols, index);
		bytea *options = path->indexinfo->opclassoptions[indexColInt];
		if (options == NULL)
		{
			return false;
		}

		/* Validate that the path can be pushed to the index. */
		if (!ValidateIndexForQualifierValue(options, secondConst->constvalue,
											BSON_INDEX_STRATEGY_DOLLAR_ORDERBY))
		{
			return false;
		}

		index++;
	}

	return true;