Function WriteIndexOrderBy

pg_documentdb/src/explain/documentdb_explain.c:991–1032

static void
WriteIndexOrderBy(pgbson_writer *writer, List *indexOrderBy, Oid indexAm, ScanDirection
				  indexorderdir)
{
	ListCell *orderByCell;
	foreach(orderByCell, indexOrderBy)
	{
		Expr *indexOrder = (Expr *) lfirst(orderByCell);

		if (IsA(indexOrder, Var) && indexAm == BTREE_AM_OID)
		{
			/* order by could by by object_id */
			Var *var = (Var *) indexOrder;
			if (var->varno == INDEX_VAR &&
				var->varattno == DOCUMENT_DATA_TABLE_OBJECT_ID_VAR_ATTR_NUMBER)
			{
				PgbsonWriterAppendInt32(writer, "_id", 3, ScanDirectionIsForward(
											indexorderdir) ? 1 : -1);
			}
		}
		else if (IsA(indexOrder, OpExpr))
		{
			OpExpr *opExpr = (OpExpr *) indexOrder;
			if (opExpr->opno == BsonOrderByIndexOperatorId() ||
				opExpr->opno == BsonOrderByReverseIndexOperatorId())
			{
				Expr *orderArg = lsecond(opExpr->args);
				if (IsA(orderArg, Const))
				{
					Const *orderConst = (Const *) orderArg;
					pgbsonelement orderElement;
					PgbsonToSinglePgbsonElementWithCollation(DatumGetPgBson(
																 orderConst->constvalue),
															 &orderElement);
					PgbsonWriterAppendValue(writer, orderElement.path,
											orderElement.pathLength,
											&orderElement.bsonValue);
				}
			}
		}
	}
}


static void