Re: Add statistics to pg_stat_wal view for wal related parameter tuning

Hi,

On 2020-12-21 13:16:50 -0800, Andres Freund wrote:
> On 2020-12-02 13:52:43 +0900, Fujii Masao wrote:
> > Pushed. Thanks!
>
> Why are wal_records/fpi long, instead of uint64?
>     long        wal_records;    /* # of WAL records produced */
>     long        wal_fpi;        /* # of WAL full page images produced */
>     uint64        wal_bytes;        /* size of WAL records produced */
>
> long is only 4 byte e.g. on windows, and it is entirely possible to wrap
> a 4 byte record counter. It's also somewhat weird that wal_bytes is
> unsigned, but the others are signed?
>
> This is made doubly weird because on the SQL level you chose to make
> wal_records, wal_fpi bigint. And wal_bytes numeric?

Some more things:
- There's both PgStat_MsgWal WalStats; and static PgStat_WalStats walStats;
  that seems *WAY* too confusing. And the former imo shouldn't be
  global.
- AdvanceXLInsertBuffer() does WalStats.m_wal_buffers_full, but as far
  as I can tell there's nothing actually sending that?

- Andres