Re: PSQL schema "describe" \dn is not escaping quotes - Mailing list pgsql-hackers

On Tue, Oct 6, 2026 at 5:18 AM surya poondla <suryapoondla4@gmail.com> wrote:
>
> Hi Peter,
>
> Thanks for v7. It applies cleanly on master, builds without warnings, and make check passes.
> The quoting fix itself looks right: both queries now take the actual schema name via appendStringLiteralConn(). I
triednames with embedded ', ", \ 
>  and ., plus mixed case. They all display correctly with the right publications footer, and \dn "e_sch1" now shows
thefooter that master silently left out. 
>
> I have a couple of  comments:
> 1. Backpatching. Nishant showed the bug goes back to PG15, but v7 also changes what \dn prints whenever a pattern is
given:
>      - each match is now its own "Schema "x"" table instead of one "List of schemas"
>      - the "(N rows)" footer is gone
>      - in non-quiet mode, a pattern with no match is now an error
>
> I don't think changes to user-visible output can go into 15–18. Could this be split into two patches? 0001 would be a
minimalescaping fix that can be backpatched, e.g. keying the footer off PQgetvalue(res, 0, 0) when exactly one row
comesback. 0002 would be the per-schema display, master only, and would probably need its own discussion. psql-ref.sgml
alsostill says matching schemas "are listed", so 0002 would need a doc update. 
>
> 2. The no-match behaviour doesn't actually match \dt. The comment says "to be same as \dt", but listTables() prints
theerror and then returns true, while listSchemas() jumps to error_return and returns false. So under ON_ERROR_STOP,
\dnnosuch now aborts a script where it used to print an empty table: 
>
>   $ psql -v ON_ERROR_STOP=1 -c '\dn e_nosuch' -c 'select 1'; echo "exit=$?"
>   Did not find any schemas named "e_nosuch".
>   exit=1
>   $ psql -v ON_ERROR_STOP=1 -c '\dt e_nosuch' -c 'select 1'; echo "exit=$?"
>   Did not find any tables named "e_nosuch".
>    ?column?
>   ----------
>           1
>   (1 row)
>
>   exit=0
>
> Also:
>      - the no-pattern message "Did not find any schemas" has no trailing period, unlike the other messages in
describe.c
>      - in quiet mode a no-match still prints the old empty "List of schemas" table, so there are two output styles
dependingon -q 
>      - pg_regress runs psql with -q, so none of the new error paths are exercised by the regression tests
>
>   3. \dn * now prints a separate table for every schema in the database, pg_catalog, pg_toast and information_schema
included.With CSV output, a multi-match pattern now produces several header rows in a row, which would break anything
thatparses the output: 
>   \pset format csv
>   \dn e_sch*
>   Name,Owner
>   e_sch1,surya
>   Name,Owner
>   e_sch2,surya
>   Name,Owner
>   e_sch3,surya
> This is one more reason to keep the redesign out of the bug fix, or at least call it out explicitly.
>
> 4. Minor issues in describeOneSchemaDetails():
>      - The footer query has no separator after the literal. With ECHO_HIDDEN it shows up as WHERE n.nspname =
'e_sch1'ORDERBY 1;. It works, but a "\n" before ORDER BY would fix it. 
>      - The footer query still uses appendPQExpBuffer() with no format arguments. Jim pointed this out for v1, but v2
onlychanged the ORDER BY line. appendPQExpBufferStr() would do. 
>      - myopt.topt.default_footer = false is only set inside the sversion >= 150000 branch, so against an older server
eachschema table still ends with "(1 row)". 
>
> 5. Tests:
>      - CREATE PUBLICATION pub_sch_1 FOR TABLES IN SCHEMA SCH_1 is unquoted, so it publishes sch_1, not "SCH_1". The
expectedoutput is correct, but a reader will probably assume the opposite. Could you add a comment, or use distinct
names?
>      - There's no coverage for \dn+ with a pattern or for names containing a backslash.
>
> Regards,
> Surya Poondla

Hi Surya,

Thanks for your review comments!

I am not is there are any the backpatching requirements for this since
its a rare (nobody raised it before me) psql display-only bug.

OTOH, I recognise your point that I need to separate the minimal
bug-fix, from where I went beyond that and tampered with existing \dn
behaviour.

I am currently splitting the patches and plan to post something new next week...

======
Kind Regards,
Peter Smith.
Fujitsu Australia