Re: Turning off HOT/Cleanup sometimes

On 4/21/15 10:04 AM, Bruce Momjian wrote:
> One thing to consider is how we handle pruning of index scans that hit
> multiple heap pages.  Do we still write X% of the pages in the table, or
> %X of the heap pages we actually access via SELECT?  With the
> write-then-skip approach, we would do X% of the pages we access, while
> with the first-X% approach, we would probably prune all of them as we
> would not be accessing most of the table.  I don't think we can do the
> first first-X% of pages and have the percentage based on the number of
> pages accessed as we have no way to know how many heap pages we will
> access from the index.

This comment made me wonder... has anyone considered handing the pruning 
work off to a bgworker, at least for SELECTs? That means the selects 
themselves wouldn't be burdened by the actual prune work, only in 
notifying the bgworker. While that's not going to be free, presumably 
it's a lot cheaper...
-- 
Jim Nasby, Data Architect, Blue Treble Consulting
Data in Trouble? Get it in Treble! http://BlueTreble.com