MODULARHASH

I believe that any instance of MODULARHASH() that appears in a projection segmentation clause is silently rewritten to HASH():
bvandiver=> create table foo (a int);
CREATE TABLE
bvandiver=> create projection foop as select * from foo segmented by modularhash(a) all nodes;
CREATE PROJECTION
bvandiver=> select projection_name,segment_expression from projections;
projection_name | segment_expression
-----------------+--------------------
foop | hash(foo.a)
(1 row)

Really ancient databases might not do this (created prior to 5.0).

If you use modularhash elsewhere, I suspect it still works as modularhash:
bvandiver=> explain select sum(a) from foo group by modularhash(a) % 4;

QUERY PLAN DESCRIPTION:

explain select sum(a) from foo group by modularhash(a) % 4;

Access Path:
+-GROUPBY HASH (GLOBAL RESEGMENT GROUPS) (LOCAL RESEGMENT GROUPS) [Cost: 265, Rows: 10K (NO STATISTICS)] (PATH ID: 1)
| Aggregates: sum(foo.a)
| Group By: (modularhash_internal(foo.a) % 4)
| Execute on: All Nodes
| +---> STORAGE ACCESS for foo [Cost: 202, Rows: 10K (NO STATISTICS)] (PATH ID: 2)
| | Projection: public.foop
| | Materialize: foo.a
| | Execute on: All Nodes

I don’t see where DBD uses modularhash()