should we document an example to set multiple libraries in shared_preload_libraries?

From: Bharath Rupireddy <bharath(dot)rupireddyforpostgres(at)gmail(dot)com>
To: PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: should we document an example to set multiple libraries in shared_preload_libraries?
Date: 2021-12-01 10:50:52
Message-ID: CALj2ACWDtGarD3=fHzivRXzq0-5Z2w4iCSE18pf2cw0q=QvKew@mail.gmail.com
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Hi,

It seems like users can try different ways to set multiple values for
shared_preload_libraries GUC even after reading the documentation
[1]), something like:
ALTER SYSTEM SET shared_preload_libraries TO
auth_delay,pg_stat_statements,sepgsql; --> correct
ALTER SYSTEM SET shared_preload_libraries =
'auth_delay','pg_stat_statements','sepgsql'; --> correct
ALTER SYSTEM SET shared_preload_libraries TO
'auth_delay','pg_stat_statements','sepgsql'; --> correct
ALTER SYSTEM SET shared_preload_libraries =
auth_delay,pg_stat_statements,sepgsql; --> wrong
ALTER SYSTEM SET shared_preload_libraries =
'auth_delay,pg_stat_statements,sepgsql'; --> wrong
ALTER SYSTEM SET shared_preload_libraries =
"auth_delay,pg_stat_statements,sepgsql"; --> wrong

The problem with the wrong parameter set command is that the ALTER
SYSTEM SET will not fail, but the server will not come up in case it
is restarted. In various locations in the documentation, we have shown
how a single value can be set, something like:
shared_preload_libraries = 'auth_delay'
shared_preload_libraries = 'pg_stat_statements'
shared_preload_libraries = 'sepgsql'

Isn't it better we document (in [1]) an example to set multiple values
to shared_preload_libraries? If okay, we can provide examples to other
GUCs local_preload_libraries and session_preload_libraries, but I'm
not in favour of it.

Thoughts?

[1] - https://www.postgresql.org/docs/devel/runtime-config-client.html#GUC-SHARED-PRELOAD-LIBRARIES

Regards,
Bharath Rupireddy.

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