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Date: Thu, 1 Dec 2022 15:12:09 +0100
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To: pgsql-bugs@lists.postgresql.org
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From: Duncan Sands <duncan.sands@deepbluecap.com>
Subject: pg_catalog.pg_get_viewdef pretty-print removes important parentheses
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When pg_catalog.pg_get_viewdef is called with pretty-print enabled, it removes 
parentheses around (DATE + INTERVAL) in the construct "(DATE + INTERVAL) AT TIME 
ZONE TZ", outputting SQL that fails to parse.  Here is an example, showing that 
the SQL output when pretty printing is off does parse, but does not parse when 
pretty printing is on.

-- EXAMPLE BEGINS

$ psql
Pager usage is off.
SET
psql (15.1 (Ubuntu 15.1-1.pgdg22.04+1))
Type "help" for help.

duncan=> CREATE VIEW pg_temp.v AS SELECT ('2022-12-01'::date + INTERVAL '1 day') 
AT TIME ZONE 'Europe/Paris';
CREATE VIEW
duncan=> SELECT pg_catalog.pg_get_viewdef('pg_temp.v'::regclass, false);
                                           pg_get_viewdef 

---------------------------------------------------------------------------------------------------
   SELECT (('2022-12-01'::date + '1 day'::interval) AT TIME ZONE 
'Europe/Paris'::text) AS timezone;
(1 row)

duncan=>   SELECT (('2022-12-01'::date + '1 day'::interval) AT TIME ZONE 
'Europe/Paris'::text) AS timezone;
         timezone
------------------------
  2022-12-02 00:00:00+01
(1 row)

duncan=> SELECT pg_catalog.pg_get_viewdef('pg_temp.v'::regclass, true);
                                          pg_get_viewdef 

-------------------------------------------------------------------------------------------------
   SELECT ('2022-12-01'::date + '1 day'::interval AT TIME ZONE 
'Europe/Paris'::text) AS timezone;
(1 row)

duncan=>   SELECT ('2022-12-01'::date + '1 day'::interval AT TIME ZONE 
'Europe/Paris'::text) AS timezone;
ERROR:  function pg_catalog.timezone(text, interval) does not exist
LINE 1: SELECT ('2022-12-01'::date + '1 day'::interval AT TIME ZONE ...
                                                        ^
HINT:  No function matches the given name and argument types. You might need to 
add explicit type casts.

-- EXAMPLE ENDS

This is annoying because psql's \ev pops up the pretty-printed version, and you 
have to add the parentheses back in by hand in order to have the view definition 
be accepted.

Best wishes, Duncan.