Re: Freeze avoidance of very large table.

On 4/6/15 12:29 PM, ktm@rice.edu wrote:
> 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.

Doh! 8 bits per byte and all that...
-- 
Jim Nasby, Data Architect, Blue Treble Consulting
Data in Trouble? Get it in Treble! http://BlueTreble.com