Re: Relpartbound, toasting and pg_class

From: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Andres Freund <andres(at)anarazel(dot)de>, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Relpartbound, toasting and pg_class
Date: 2017-06-12 21:59:05
Message-ID: 20170612215905.xhpebxwinz3va5yz@alvherre.pgsql
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Tom Lane wrote:
> Andres Freund <andres(at)anarazel(dot)de> writes:
> > On 2017-06-12 17:10:28 -0400, Peter Eisentraut wrote:
> >> Cases where relacl became too large have been known to exist. I'm not
> >> sure whether relpartbound can really be that large to change the
> >> scenario significantly.
>
> > Because it's further increasing the size by something unbounded in size,
> > which'll not uncommonly be large? It makes a fair amount of sense to
> > partition by multiple columns at once (using the expression syntax).
>
> How about gathering some actual evidence on the point --- ie, how big
> a partition expression do you need to make it fall over?

You'd need a 2kB expression (after compression) in
relpartbound before you hit a problem here. I wouldn't worry about it
at this stage ...

Not on point, but this conversation reminded me of
https://www.commandprompt.com/blog/grant_schema_usage_to_2500_users_no_can_do/
wherein you needed 2500 roles in an ACL column before it became a
problem -- and the project's stance is not to bother supporting that
case.

--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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