Re: Should pg_current_wal_location() become pg_current_wal_lsn()

At Mon, 10 Apr 2017 19:26:11 +1200, David Rowley <david.rowley@2ndquadrant.com> wrote in <CAKJS1f8O0njDKe8ePFQ-LK5-EjwThsDws6ohJ-+c6nWK+oUxtg@mail.gmail.com>
> ... and of course the other functions matching *wal*location*
> 
> My thoughts here are that we're already breaking backward
> compatibility of these functions for PG10, so thought we might want to
> use this as an opportunity to fix the naming a bit more.
> 
> I feel that the "location" word not the best choice.  We also have a
> function called pg_tablespace_location() to give us the path that a
> tablespace is stored in, so I could understand anyone who's confused
> about what pg_current_wal_location() might do if they're looking at
> the function name only, and not the docs.
> 
> For me, "lsn" suits these function names much better, so I'd like to
> see what other's think.
> 
> It would be sad to miss this opportunity without at least discussing this first.
> 
> The functions in question are:
> 
> postgres=# \dfS *wal*location*
>                                        List of functions
>    Schema   |              Name              | Result data type |
> Argument data types |  Type
> ------------+--------------------------------+------------------+---------------------+--------
>  pg_catalog | pg_current_wal_flush_location  | pg_lsn           |
>                | normal
>  pg_catalog | pg_current_wal_insert_location | pg_lsn           |
>                | normal
>  pg_catalog | pg_current_wal_location        | pg_lsn           |
>                | normal
>  pg_catalog | pg_last_wal_receive_location   | pg_lsn           |
>                | normal
>  pg_catalog | pg_last_wal_replay_location    | pg_lsn           |
>                | normal
>  pg_catalog | pg_wal_location_diff           | numeric          |
> pg_lsn, pg_lsn      | normal
> (6 rows)
> 
> Opinions?

Similariliy, these columns may need renaming.

s=# select attname, attrelid::regclass from pg_attribute where attname like '%location%';
     attname     |      attrelid       
-----------------+---------------------
 sent_location   | pg_stat_replication
 write_location  | pg_stat_replication
 flush_location  | pg_stat_replication
 replay_location | pg_stat_replication
(4 rows)


Currently the following functions and columns are using 'lsn'.

=# \dfS *lsn*
                             List of functions
   Schema   |    Name     | Result data type | Argument data types |  Type  
------------+-------------+------------------+---------------------+--------
 pg_catalog | pg_lsn_cmp  | integer          | pg_lsn, pg_lsn      | normal
 pg_catalog | pg_lsn_eq   | boolean          | pg_lsn, pg_lsn      | normal
...
 pg_catalog | pg_lsn_recv | pg_lsn           | internal            | normal
 pg_catalog | pg_lsn_send | bytea            | pg_lsn              | normal
(13 rows)


=# select distinct attname from pg_attribute where attname like '%lsn%';
       attname       
---------------------
 confirmed_flush_lsn
 latest_end_lsn
 local_lsn
 receive_start_lsn
 received_lsn
 remote_lsn
 restart_lsn
 srsublsn
(8 rows)


Feature is already frozen, but this seems inconsistent a bit..

regards,

-- 
Kyotaro Horiguchi
NTT Open Source Software Center