| From: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
|---|---|
| To: | Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com> |
| Cc: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz>, Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: min_safe_lsn column in pg_replication_slots view |
| Date: | 2020-06-30 18:09:22 |
| Message-ID: | 20200630180922.GA13453@alvherre.pgsql |
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| Lists: | pgsql-hackers |
On 2020-Jun-30, Fujii Masao wrote:
> Sorry this is not true. That distance can be calculated without those operators.
> For example,
>
> SELECT restart_lsn - pg_current_wal_lsn() + (SELECT setting::numeric * 1024 * 1024 FROM pg_settings WHERE name = 'max_slot_wal_keep_size') distance FROM pg_replication_slots;
>
> If the calculated distance is small or negative value, which means that
> we may lose some required WAL files. So in this case it's worth considering
> to increase max_slot_wal_keep_size.
... OK, but you're forgetting wal_keep_segments.
> I still think it's better and more helpful to display something like
> that distance in pg_replication_slots rather than making each user
> calculate it...
Agreed.
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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