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From: jian he <jian.universality@gmail.com>
Date: Fri, 20 Dec 2024 10:53:06 +0800
Message-ID: <CACJufxGvy6QNMwZ5xd=L31F+4Rr6aXCASeMFyLZS+TVssK5+vA@mail.gmail.com>
Subject: Re: in BeginCopyTo make materialized view using COPY TO instead of
 COPY (query).
To: Michael Paquier <michael@paquier.xyz>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
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On Fri, Dec 20, 2024 at 8:02=E2=80=AFAM Michael Paquier <michael@paquier.xy=
z> wrote:
>
> On Thu, Dec 19, 2024 at 02:28:21PM +0800, jian he wrote:
> > Since materialized views have physical storage,
> >
> > we can make materialized views also using COPY table_name, instead of
> > COPY(query).
> >
> > Some simple tests show around %3.7 or 4.3% speed up.
>
> This restriction comes from 3bf3ab8c5636 as such relations may not be
> scannable when they have no data, no?  Perhaps this restriction could
> be lifted, but I'd suggest to dig more into the lists, there should be
> arguments and ideas explaining what could be done in this case
> (spoiler: I did not look at that).
> --


Thanks for the suggestion.
it was mentioned in link [1] and [2].

[1] https://www.postgresql.org/message-id/flat/8967.1353167301%40sss.pgh.pa=
.us#f5e947cfa9357dba780d238f1c5f6932
[2] https://www.postgresql.org/message-id/20121116162558.90150%40gmx.com


Basically we want to have the two directions of COPY.
so
copy the_materialized_view to stdout;
copy the_materialized_view  from stdin;

both will work fine.
obviously "copy the_materialized_view  from stdin; " will not work.