Make comments reflect that omission of SPI_gettypmod() is intentional.

src/backend/executor/spi.c

@@ -940,6 +940,12 @@ SPI_gettype(TupleDesc tupdesc, int fnumber)
 	return result;
 }
 
+/*
+ * Get the data type OID for a column.
+ *
+ * There's nothing similar for typmod and typcollation.  The rare consumers
+ * thereof should inspect the TupleDesc directly.
+ */
 Oid
 SPI_gettypeid(TupleDesc tupdesc, int fnumber)
 {

src/pl/plpgsql/src/pl_exec.c

@@ -4446,7 +4446,6 @@ exec_eval_datum(PLpgSQL_execstate *estate,
 							 errmsg("record \"%s\" has no field \"%s\"",
 									rec->refname, recfield->fieldname)));
 				*typeid = SPI_gettypeid(rec->tupdesc, fno);
-				/* XXX there's no SPI_gettypmod, for some reason */
 				if (fno > 0)
 					*typetypmod = rec->tupdesc->attrs[fno - 1]->atttypmod;
 				else
@@ -4623,12 +4622,10 @@ exec_get_datum_type_info(PLpgSQL_execstate *estate,
 							 errmsg("record \"%s\" has no field \"%s\"",
 									rec->refname, recfield->fieldname)));
 				*typeid = SPI_gettypeid(rec->tupdesc, fno);
-				/* XXX there's no SPI_gettypmod, for some reason */
 				if (fno > 0)
 					*typmod = rec->tupdesc->attrs[fno - 1]->atttypmod;
 				else
 					*typmod = -1;
-				/* XXX there's no SPI_getcollation either */
 				if (fno > 0)
 					*collation = rec->tupdesc->attrs[fno - 1]->attcollation;
 				else	/* no system column types have collation */