"Nicolas Barbier" <[EMAIL PROTECTED]> writes:
> 2006/4/3, Tom Lane <[EMAIL PROTECTED]>:
>> AFAICS there are no circumstances, ever, in which update-in-place is
>> "safe". (No transaction can guarantee that it will commit.)
> Updates to row values that did not "escape" the currect transaction
> yet (ie, rows that were created by or have their last value written by
> the current transaction).
Wrong, because MVCC also applies within transactions: a snapshot having
a lower command counter than what you are executing at should not see
your change. A typical example of this is that an update scan must not
see tuples generated by triggers fired by that scan.
regards, tom lane
---------------------------(end of broadcast)---------------------------
TIP 9: In versions below 8.0, the planner will ignore your desire to
choose an index scan if your joining column's datatypes do not
match
