From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Cc: jgdr@dalibo.com
Cc: andres@anarazel.de
Cc: michael@paquier.xyz
Cc: sawada.mshk@gmail.com
Cc: peter.eisentraut@2ndquadrant.com
Cc: pgsql-hackers@lists.postgresql.org
Cc: thomas.munro@enterprisedb.com
Cc: sk@zsrv.org
Cc: michael.paquier@gmail.com
Subject: Re: [HACKERS] Restricting maximum keep segments by repslots
Date: Mon, 6 Apr 2020 12:54:56 -0400
Message-ID: <20200406165456.GA4951@alvherre.pgsql> (raw)
In-Reply-To: <20200406.185027.648866525989475817.horikyota.ntt@gmail.com>
On 2020-Apr-06, Kyotaro Horiguchi wrote:
> > * Andres complained that the "distance" column was not a great value to
> > expose (20171106132050.6apzynxrqrzghb4r@alap3.anarazel.de). That's
> > right: it changes both by the insertion LSN as well as the slot's
> > consumption. Maybe we can expose the earliest live LSN (start of the
> > earliest segment?) as a new column. It'll be the same for all slots,
> > I suppose, but we don't care, do we?
>
> I don't care as far as users can calculate the "remain" of individual
> slots (that is, how far the current LSN can advance before the slot
> loses data). But the "earliest live LSN (EL-LSN) is really not
> relevant to the safeness of each slot. The distance from EL-LSN to
> restart_lsn or the current LSN doesn't generally suggest the safeness
> of individual slots. The only relevance would be if the distance from
> EL-LSN to the current LSN is close to max_slot_wal_keep_size, the most
> lagged slot could die in a short term.
Thanks for the revised version. Please note that you forgot to "git
add" the test file, to it's not in the patch.
I'm reviewing the patch now.
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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To: pgsql-hackers@postgresql.org
Cc: alvherre@2ndquadrant.com, horikyota.ntt@gmail.com, jgdr@dalibo.com, andres@anarazel.de, michael@paquier.xyz, sawada.mshk@gmail.com, peter.eisentraut@2ndquadrant.com, pgsql-hackers@lists.postgresql.org, thomas.munro@enterprisedb.com, sk@zsrv.org, michael.paquier@gmail.com
Subject: Re: [HACKERS] Restricting maximum keep segments by repslots
In-Reply-To: <20200406165456.GA4951@alvherre.pgsql>
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