Re: [SQL] [GENERAL] CURRENT_TIMESTAMP

OK, are we agreed to leave CURRENT_TIMESTAMP/now() alone and just add
now("string")?  If no one replies, I will assume that is a yes and I
will add it to TODO.

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Michael Paesold wrote:
> Bruce Momjian <pgman@candle.pha.pa.us> wrote:
> 
> > > That is a very good point. At least with serializable transactions it
> seems
> > > perfectly reasonable to return a frozen CURRENT_TIMESTAMP. What do you
> think
> > > about read-commited level? Can time be commited? ;-)
> > > It would be even more surprising to new users if the implementation of
> > > CURRENT_TIMESTAMP would depend on trx serialization level.
> >
> > Yes, CURRENT_TIMESTAMP changing based on transaction serializable/read
> > commited would be quite confusing.  Also, because our default is read
> > committed, we would end up with CURRENT_TIMESTAMP being statement level,
> > which actually does give us a logical place to allow CURRENT_TIMESTAMP
> > to change, but I thought people voted against that.
> >
> > However, imagine a query that used CURRENT_TIMESTAMP in the WHERE clause
> > to find items that were not in the future.  Would a CURRENT_TIMESTAMP
> > test in a multi-statement transaction want to check based on transaction
> > start, or on the tuples visible at the time the statement started?
> 
> Well, in a serializable transaction there would be no difference at all, at
> least if CURRENT_TIMESTAMP is consistent within the transaction. Any changes
> outside the transaction after SetQuerySnapshot would not be seen by the
> transaction anyway.
> 
> In read-commited, I think it's different. If CURRENT_TIMESTAMP is frozen,
> than the behavior would be the same as in serializable level, if
> CURRENT_TIMESTAMP advances with each statement, the result would also
> change. That is an inherent problem with read-commited though and has not so
> much to do with the timestamp behavior.
> 
> Regards,
> Michael Paesold
> 
> 
> 
> 

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