From: | Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> |
---|---|
To: | Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com> |
Cc: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Freezing without cleanup lock |
Date: | 2015-10-26 14:06:26 |
Message-ID: | CAD21AoC16QVUBEXJWyaHA4x6-jW0LXAWSLQdWh6V21kYi4eErw@mail.gmail.com |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
On Mon, Oct 26, 2015 at 4:39 AM, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com> wrote:
> On 10/22/15 6:39 PM, Alvaro Herrera wrote:
>>
>> Jim Nasby wrote:
>>
>>> That would be the minimal-impact version, yes. But I suspect if we went
>>> through the trouble to do that, it would be just as easy to attempt the
>>> freeze regardless of what scan_all is set to.
>>
>>
>> You mean if !scan_all we conditional-get the cleanup lock, if we get it
>> then prune, if not then freeze? That seems nice on paper but I think
>> it's useless because unless scan_all is true, then relfrozenxid doesn't
>> advance anyway.
>
>
> Actually, advancing relfrozenxid only depends on having hit all pages in the
> table, which can happen even if !scan_all. Aside from that, once the freeze
> map hits this would be useful in setting bits there.
Yeah, when the all pages have frozen totally (that is, when
scanned_page + vm_skipped_frozen_page equals relpages), relfrozenxid
will be updated. But the item pointers of page that are frozen by such
logic are never pruned.
Regards,
--
Masahiko Sawada
From | Date | Subject | |
---|---|---|---|
Next Message | Tom Lane | 2015-10-26 14:18:32 | Re: Proposal: Trigonometric functions in degrees |
Previous Message | Robert Haas | 2015-10-26 13:18:00 | Re: Patch (3): Implement failover on libpq connect level. |