Re: Freeze avoidance of very large table.

On 4/23/15 11:06 AM, Petr Jelinek wrote:
> On 23/04/15 17:45, Bruce Momjian wrote:
>> On Thu, Apr 23, 2015 at 09:45:38AM -0400, Robert Haas wrote:
>> Agreed, no extra file, and the same write volume as currently.  It would
>> also match pg_clog, which uses two bits per transaction --- maybe we can
>> reuse some of that code.
>>
>
> Yeah, this approach seems promising. We probably can't reuse code from
> clog because the usage pattern is different (key for clog is xid, while
> for visibility/freeze map ctid is used). But visibility map storage
> layer is pretty simple so it should be easy to extend it for this use.

Actually, there may be some bit manipulation functions we could reuse; 
things like efficiently counting how many things in a byte are set. 
Probably doesn't make sense to fully refactor it, but at least CLOG is a 
good source for cut/paste/whack.
-- 
Jim Nasby, Data Architect, Blue Treble Consulting
Data in Trouble? Get it in Treble! http://BlueTreble.com