From: Tom Lane <tgl@sss.pgh.pa.us>
To: Yugo Nagata <nagata@sraoss.co.jp>
cc: pgsql-hackers@postgresql.org
Subject: Re: EphemeralNamedRelation and materialized view
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References: <20240726160714.e74d0db579f2c017e1ca0b7e@sraoss.co.jp>
Comments: In-reply-to Yugo Nagata <nagata@sraoss.co.jp>
	message dated "Fri, 26 Jul 2024 16:07:14 +0900"
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Date: Sun, 03 Nov 2024 13:42:33 -0500
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Yugo Nagata <nagata@sraoss.co.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