Re: Schema variables - new implementation for Postgres 15 (typo)

I've accumulated another collection of various questions and comments. As a
side note I'm getting a good feeling about this patch, those part I've read so
far looks good to me.

* I've suddenly realized one could use pseudo types for variables, and
it not always works. E.g.:

=# create variable pseudo_array anyarray;
=# select pseudo_array;
pseudo_array
--------------
NULL

=# let pseudo_array = ARRAY[1, 2, 3];
ERROR: 42804: target session variable is of type anyarray but expression is of type integer[]
LOCATION: svariableStartupReceiver, svariableReceiver.c:79

=# create variable pseudo_unknown unknown;
=# select pseudo_unknown;
ERROR: XX000: failed to find conversion function from unknown to text
LOCATION: coerce_type, parse_coerce.c:542

Is it supposed to be like this, or something is missing?

* I think it was already mentioned in the thread, there seems to be not a
single usage of CHECK_FOR_INTERRUPTS in session_variable.c . But some number
of loops over the sessionvars are implemented, are they always going to be
small enough to not make any troubles?

* sync_sessionvars_all explains why is it necessary to copy xact_recheck_varids:

When we check the variables, the system cache can be invalidated,
and xact_recheck_varids can be enhanced.

I'm not quite following what the "enhancement" part is about? Is
xact_recheck_varids could be somehow updated concurrently with the loop?

* A small typo

diff --git a/src/backend/commands/session_variable.c b/src/backend/commands/session_variable.c
--- a/src/backend/commands/session_variable.c
+++ b/src/backend/commands/session_variable.c
@@ -485,7 +485,7 @@ sync_sessionvars_all(bool filter_lxid)

/*
* When we check the variables, the system cache can be invalidated,
- * and xac_recheck_varids can be enhanced. We want to iterate
+ * and xact_recheck_varids can be enhanced. We want to iterate

NOTE: The commentaries above were made based on the previous patch version, but
it looks like those aspects were not changed.