Re: add log messages when replication slots become active and inactive (was Re: Is it worth adding ReplicationSlot active_pid to ReplicationSlotPersistentData?)

Here are some review comments for patch v13-0001.

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doc/src/sgml/config.sgml

1.
        <para>
-        Causes each replication command to be logged in the server log.
-        See <xref linkend="protocol-replication"/> for more information about
-        replication command. The default value is <literal>off</literal>.
-        Only superusers and users with the appropriate <literal>SET</literal>
-        privilege can change this setting.
+        Causes each replication command and slot acquisition/release to be
+        logged in the server log. See <xref linkend="protocol-replication"/>
+        for more information about replication command. The default value is
+        <literal>off</literal>. Only superusers and users with the appropriate
+        <literal>SET</literal> privilege can change this setting.
        </para>

Should that also mention about walsender?

e.g.
"and slot acquisition/release" ==> "and <literal>walsender</literal>
slot acquisition/release"

======
src/backend/replication/slot.c

2. ReplicationSlotAcquire

  if (SlotIsLogical(s))
  pgstat_acquire_replslot(s);
+
+ if (am_walsender)
+ ereport(log_replication_commands ? LOG : DEBUG1,
+ errmsg_internal("acquired %s replication slot \"%s\"",
+ SlotIsPhysical(MyReplicationSlot) ? "physical" : "logical",
+ NameStr(MyReplicationSlot->data.name)));

2a.
Instead of calling SlotIsLogical() and then again calling
SlotIsPhysical(), it might be better to assign this one time to a
local variable.

~

2b.
IMO it is better to continue using variable 's' here instead of
'MyReplicationSlot'. Code is not only shorter but is also consistent
with the rest of the function which never uses MyReplicationSlot, even
in the places where it could have.

~

SUGGESTION (for #2a and #2b)
is_logical = SlotIsLogical(s);
if (is_logical)
  pgstat_acquire_replslot(s);

if (am_walsender)
  ereport(log_replication_commands ? LOG : DEBUG1,
    errmsg_internal("acquired %s replication slot \"%s\"",
      is_logical ? "logical" : "physical", NameStr(s->data.name)));

~~~

3. ReplicationSlotRelease

 ReplicationSlotRelease(void)
 {
  ReplicationSlot *slot = MyReplicationSlot;
+ char    *slotname = NULL; /* keep compiler quiet */
+ bool is_physical = false; /* keep compiler quiet */

  Assert(slot != NULL && slot->active_pid != 0);

+ if (am_walsender)
+ {
+ slotname = pstrdup(NameStr(MyReplicationSlot->data.name));
+ is_physical = SlotIsPhysical(MyReplicationSlot);
+ }
+

3a.
Notice 'MyReplicationSlot' is already assigned to the local 'slot'
variable, so IMO it is better if this new code also uses that 'slot'
variable for consistency with the rest of the function.

~

3b.
Consider flipping the flag to be 'is_logical' instead of
'is_physical', so the ereport substitution will match the other
ReplicationSlotAcquirecode suggested above (#2a).

~

SUGGESTION (For #3a and #3b)
if (am_walsender)
{
  slotname = pstrdup(NameStr(slot->data.name));
  is_logical = SlotIsLogical(slot);
}

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Kind Regards,
Peter Smith.
Fujitsu Australia