Heikki Linnakangas <[EMAIL PROTECTED]> writes:
> What's the verdict on relaxing the "live tuple's ctid doesn't change 
> rule"?

I think that's unacceptable; it is known that that will break the ODBC
and JDBC drivers, as well as any other programs that make use of the
ctid for re-finding a tuple they read earlier in the same transaction.
We have not only never deprecated client-side use of ctid for this, but
actively encouraged it, for instance by going out of our way to support
fast access for queries "WHERE ctid = 'constant'".

What's more, your proposal would break plain old UPDATE and DELETE,
as well as SELECT FOR UPDATE, none of which promise to hold a pin
continuously on every page containing a tuple they might decide to
revisit (by ctid) later.  Are you prepared to disallow hash join and
sort/merge join in all such queries?

                        regards, tom lane

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