Re: I/O on select count(*)

[Greg Smith <gsmith(at)gregsmith(dot)com>]

I just collected all the good internals information included in this 
thread and popped it onto http://wiki.postgresql.org/wiki/Hint_Bits where 
I'll continue to hack away at the text until it's readable.  Thanks to 
everyone who answered my questions here, that's good progress toward 
clearing up a very underdocumented area.

I note a couple of potential TODO items not on the official list yet that 
came up during this discussion:

-Smooth latency spikes when switching commit log pages by preallocating 
cleared pages before they are needed

-Improve bulk loading by setting "frozen" hint bits for tuple inserts 
which occur within the same database transaction as the creation of the 
table into which they're being inserted

Did I miss anything?  I think everything brought up falls either into one 
of those two or the existing "Consider having the background writer update 
the transaction status hint bits..." TODO.

--
* Greg Smith gsmith(at)gregsmith(dot)com http://www.gregsmith.com Baltimore, MD