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Please clarify docs on user-defined settings for SET and RESET 2+ messages / 2 participants [nested] [flat]
* Please clarify docs on user-defined settings for SET and RESET @ 2025-04-22 05:57 PG Doc comments form <noreply@postgresql.org> 2025-04-22 13:47 ` Re: Please clarify docs on user-defined settings for SET and RESET David G. Johnston <david.g.johnston@gmail.com> 0 siblings, 1 reply; 2+ messages in thread From: PG Doc comments form @ 2025-04-22 05:57 UTC (permalink / raw) To: pgsql-docs@lists.postgresql.org; +Cc: jens.troeger@light-speed.de The following documentation comment has been logged on the website: Page: https://www.postgresql.org/docs/17/sql-set.html Description: Hello, I'm reading through and playing with the SET and RESET docs and I'm somewhat unclear about the behavior of arbitrary user settings that *don't* have a session default. For example a user defined setting is not available: > psql -h localhost -U postgres psql (14.17) Type "help" for help. postgres=# select current_setting('foo.bar'); ERROR: unrecognized configuration parameter "foo.bar" postgres=# select current_setting('foo.bar', true); current_setting ----------------- (1 row) postgres=# select current_setting('foo.bar', true) is null; ?column? ---------- t (1 row) And then I set it: postgres=# set foo.bar = 'foo!bar'; SET postgres=# select current_setting('foo.bar'); current_setting ----------------- foo!bar (1 row) And then I reset it to… what? postgres=# reset foo.bar; RESET postgres=# select current_setting('foo.bar'); current_setting ----------------- (1 row) postgres=# select current_setting('foo.bar') = ''; ?column? ---------- t (1 row) It seems that the assumed/implied default value for settings that did not exist for a session is the empty string? It would be useful to document that behavior explicitly. We can take this further: > psql -h localhost -U postgres psql (14.17) Type "help" for help. postgres=# select current_setting('foo.bar', true) is null; ?column? ---------- t (1 row) postgres=# select current_setting('foo.bar', true) = ''; ?column? ---------- (1 row) postgres=# reset foo.bar; -- Same as: SET foo.bar TO DEFAULT RESET postgres=# select current_setting('foo.bar', true) is null; ?column? ---------- f (1 row) postgres=# select current_setting('foo.bar', true) = ''; ?column? ---------- t (1 row) Note how the value & type of the user setting changes, somewhat unexpectedly (to me). Furthermore, it seems impossible to actually *remove* such a user defined settings completely, correct? That too, I miss stated explicitly in the documentation. Much thanks! Jens ^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: Please clarify docs on user-defined settings for SET and RESET 2025-04-22 05:57 Please clarify docs on user-defined settings for SET and RESET PG Doc comments form <noreply@postgresql.org> @ 2025-04-22 13:47 ` David G. Johnston <david.g.johnston@gmail.com> 0 siblings, 0 replies; 2+ messages in thread From: David G. Johnston @ 2025-04-22 13:47 UTC (permalink / raw) To: jens.troeger@light-speed.de <jens.troeger@light-speed.de>; pgsql-docs@lists.postgresql.org <pgsql-docs@lists.postgresql.org> On Monday, April 21, 2025, PG Doc comments form <noreply@postgresql.org> wrote: > > > It seems that the assumed/implied default value for settings that did not > exist for a session is the empty string? It would be useful to document > that > behavior explicitly. This is presently being worked on. Some changes have made it into the v18 docs already. > > Furthermore, it seems impossible to actually *remove* such a user defined > settings completely, correct? That too, I miss stated explicitly in the > documentation. > Correct. The null is not the value of the setting, it is being provided instead of producing a “setting does not exist” error. The system never forgets a setting once set (within a session). Reset restores a setting to its default value, which for text is the empty string. David J. ^ permalink raw reply [nested|flat] 2+ messages in thread
end of thread, other threads:[~2025-04-22 13:47 UTC | newest] Thread overview: 2+ messages (download: mbox mbox.gz follow: Atom feed) -- links below jump to the message on this page -- 2025-04-22 05:57 Please clarify docs on user-defined settings for SET and RESET PG Doc comments form <noreply@postgresql.org> 2025-04-22 13:47 ` David G. Johnston <david.g.johnston@gmail.com>
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