| From: | "ktm(at)rice(dot)edu" <ktm(at)rice(dot)edu> |
|---|---|
| To: | Jim Nasby <Jim(dot)Nasby(at)BlueTreble(dot)com> |
| Cc: | Sawada Masahiko <sawada(dot)mshk(at)gmail(dot)com>, Jeff Janes <jeff(dot)janes(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Freeze avoidance of very large table. |
| Date: | 2015-04-06 17:29:51 |
| Message-ID: | 20150406172951.GE11688@aart.rice.edu |
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| Thread: | |
| Lists: | pgsql-hackers |
On Mon, Apr 06, 2015 at 12:07:47PM -0500, Jim Nasby wrote:
> ...
> As I understand it, the goal here is to prevent huge amounts of
> periodic freeze work due to XID wraparound. I don't think we need
> the Freeze state to accomplish that.
>
> With a single bit per page in the Frozen Map, checking a 800GB table
> would require reading a mere 100MB of FM. That's pretty tiny, and
> largely accomplishes the goal.
>
> Obviously it would be nice to eliminate even that 100MB read, but I
> suggest you leave that for a 3rd patch. I think you'll find that
> just getting the first 2 accomplished will be a significant amount
> of work.
>
Hi,
I may have my math wrong, but 800GB ~ 100M pages or 12.5MB and not
100MB.
Regards,
Ken
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