DANTE Alexandra <Alexandra.Dante@bull.net> writes:
> - during a SELECT query on a tuple just updated and commited, does
> the executor first detect the old tuple and then via the c_tid link go
> to the new version of the tuple ? or go directly to the new version ?
Neither. SELECT doesn't care about update relationships, it just
returns whatever row version is current according to its snapshot.
It's only UPDATE/DELETE that are constrained to act on the most
current version of each row.
regards, tom lane