extended stats objects are the only thing written like "%s"."%s"

commit a4d75c86bf15220df22de0a92c819ecef9db3849
Author: Tomas Vondra <tomas(dot)vondra(at)postgresql(dot)org>
Date: Fri Mar 26 23:22:01 2021 +0100

Extended statistics on expressions

This commit added to psql/describe.c:

+ /* statistics object name (qualified with namespace) */
+ appendPQExpBuffer(&buf, "\"%s\".\"%s\"",
+ PQgetvalue(result, i, 2),
+ PQgetvalue(result, i, 3));

Everywhere else the double quotes are around the whole "schema.object" rather
than both separately: "schema"."object". The code handling servers before v14
has the same thing, since:

commit bc085205c8a425fcaa54e27c6dcd83101130439b
Author: Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>
Date: Fri May 12 14:59:23 2017 -0300

Change CREATE STATISTICS syntax

src/bin/psql/describe.c- /* statistics object name (qualified with namespace) */
src/bin/psql/describe.c: appendPQExpBuffer(&buf, "\"%s\".\"%s\" (",
src/bin/psql/describe.c- PQgetvalue(result, i, 2),
src/bin/psql/describe.c- PQgetvalue(result, i, 3));

That seems to have been first added in the patch here, but AFAIT not
specifically discussed.
https://www.postgresql.org/message-id/20170511221330.5akgbsoyx6wm4u34%40alvherre.pgsql

At the time the patch was commited, it was the only place that used
"schema"."object":
$ git show bc085205c8a425fcaa54e27c6dcd83101130439b:src/bin/psql/describe.c |grep '\\"\.\\"'
appendPQExpBuffer(&buf, "\"%s\".\"%s\" (",

And it's still the only place, not just in describe.c, but the entire project.
$ git grep -Fc '\"%s\".\"%s\"' '*.c'
src/bin/psql/describe.c:2

I actually don't like writing it as "a.b" since it doesn't work to copy+paste
that, because that means an object called "a.b" in the default schema.
But I think for consistency it should be done the same here as everywhere else.

I noticed that Peter E recently changed amcheck in the direction of consistency:
| 4279e5bc8c pg_amcheck: Message style and structuring improvements

I propose to change extended stats objects to be shown the same as everywhere
else, with double quotes around the whole %s.%s:
$ git grep '\\"%s\.%s\\"' '*.c' |wc -l
126

This affects 9 lines of output in regression tests.

Note that check constraints and indexes have the same schema as their table, so
\d doesn't show a schema at all, and quotes the name of the object. That
distinction may be relevant to how stats objects ended up being quoted like
this.

--
Justin