Re: Allow escape in application_name (was: [postgres_fdw] add local pid to fallback_application_name)

On 2021/09/01 19:04, kuroda(dot)hayato(at)fujitsu(dot)com wrote:
> OK, I split and attached like that. 0001 adds new GUC, and
> 0002 allows to accept escapes.

Thanks for splitting and updating the patches!

Here are the comments for 0001 patch.

- /* Use "postgres_fdw" as fallback_application_name. */
+ /* Use GUC paramter if set */
+ if (pgfdw_application_name && *pgfdw_application_name != '\0')

This GUC parameter should be set after the options of foreign server
are set so that its setting can override the server-level ones.
Isn't it better to comment this?

+static bool
+check_pgfdw_application_name(char **newval, void **extra, GucSource source)
+{
+ /* Only allow clean ASCII chars in the application name */
+ if (*newval)
+ pg_clean_ascii(*newval);
+ return true;

Do we really need this check hook? Even without that, any non-ASCII characters
in application_name would be replaced with "?" in the foreign PostgreSQL server
when it's passed to that.

On the other hand, if it's really necessary, application_name set in foreign
server object also needs to be processed in the same way.

+ NULL,
+ PGC_USERSET,
+ GUC_IS_NAME,

Why is GUC_IS_NAME flag necessary?

postgres_fdw.application_name overrides application_name set in foreign server object.
Shouldn't this information be documented?

Isn't it better to have the regression test for this feature?

Regards,

--
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION