Re: EphemeralNamedRelation and materialized view

Yugo Nagata <nagata(at)sraoss(dot)co(dot)jp> writes:
> While looking into the commit b4da732fd64e936970f38c792f8b32c4bdf2bcd5,
> I noticed that we can create a materialized view using Ephemeral Named
> Relation in PostgreSQL 16 or earler.

Yeah, we should reject that, but I feel like this patch is not
ambitious enough, because the 17-and-up behavior isn't exactly
polished either.

I tried variants of this function in HEAD:

1. With "create table mv as select * from enr", it works and
does what you'd expect.

2. With "create view mv as select * from enr", you get

regression=# insert into tbl values (10);
ERROR: relation "enr" does not exist
LINE 1: create view mv as select * from enr
^
QUERY: create view mv as select * from enr
CONTEXT: PL/pgSQL function f() line 2 at SQL statement
regression=# \errverbose
ERROR: 42P01: relation "enr" does not exist
LINE 1: create view mv as select * from enr
^
QUERY: create view mv as select * from enr
CONTEXT: PL/pgSQL function f() line 2 at SQL statement
LOCATION: parserOpenTable, parse_relation.c:1452

3. With "create materialized view ..." you get

regression=# insert into tbl values (10);
ERROR: executor could not find named tuplestore "enr"
CONTEXT: SQL statement "create materialized view mv as select * from enr"
PL/pgSQL function f() line 2 at SQL statement
regression=# \errverbose
ERROR: XX000: executor could not find named tuplestore "enr"
CONTEXT: SQL statement "create materialized view mv as select * from enr"
PL/pgSQL function f() line 2 at SQL statement
LOCATION: ExecInitNamedTuplestoreScan, nodeNamedtuplestorescan.c:107

I don't think hitting an internal error is good enough.
Why doesn't this case act like case 2?

You could even argue that case 2 isn't good enough either,
and we should be delivering a specific error message saying
that an ENR can't be used in a view/matview. To do that,
we'd likely need to pass down the QueryEnvironment in more
places not fewer.

regards, tom lane