> There's been some speculation about allowing a standby server to execute
> purely read-only operations, but it's just speculation so far.
To add some more speculations, I wonder if that can be workable at
all... given that the data pages are overwritten by WAL records, and not
under transactional control of the standby server, how can you ensure
that a read only transaction on the standby will see a consistent
snapshot of the data ? It is possible that some data on a page which
should be visible for the read only transaction is overwritten or even
deleted by some incoming WAL record.
I think the only solution would be to only recover up to the oldest
local transaction's start time, but then if you have long running
transactions on the stand-by, you'll also have long delays in
recovery... which might not be what people want...
Cheers,
Csaba.