"Dann Corbit" <DCorbit@connx.com> writes:
> How many accounts are 90 days overdue? Bill says 78 and Frank says 82.
> Who is right and how can we know?
If Bill and Frank look at exactly the same instant (ie, from read-only
transactions started at the same time), they will get the same answer.
If they are looking from transactions started at different times, or
from transactions that have themselves added/removed rows, they won't
necessarily get the same answer. That does not make either answer
wrong, just a reflection of the snapshots they are seeing.
regards, tom lane
