| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com> |
| Cc: | Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, Sawada Masahiko <sawada(dot)mshk(at)gmail(dot)com>, Greg Stark <stark(at)mit(dot)edu>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com> |
| Subject: | Re: Freeze avoidance of very large table. |
| Date: | 2015-04-28 12:11:01 |
| Message-ID: | CA+TgmoZr=gOPPoUdfWZw+v6TLZ1zpvyS8_YNe0CS8vwQkrnxxw@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Fri, Apr 24, 2015 at 4:09 PM, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>
wrote:>>> When I read that I think about something configurable at
>>> relation-level.There are cases where you may want to have more
>>> granularity of this information at block level by having the VM slots
>>> to track less blocks than 32, and vice-versa.
>>
>> What are those cases? To me that sounds like making things
>> complicated to no obvious benefit.
>
> Tables that get few/no dead tuples, like bulk insert tables. You'll have
> large sections of blocks with the same visibility.
I don't see any reason why that would require different granularity.
> I suspect the added code to allow setting 1 bit for multiple pages without
> having to lock all those pages simultaneously will probably outweigh making
> this a reloption anyway.
That's a completely unrelated issue.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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