Re: WAL Bypass for indexes

"Nicolas Barbier" <nicolas(dot)barbier(at)gmail(dot)com> writes:
> 2006/4/3, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:
>> 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