"Jenny -" <nat_lazy@hotmail.com> writes:
>> TupleTables are just temporary data structures to hold transiently
>> created tuples during execution of a query. There's usually one for
>> each plan node.
> The TupleTable will exist for the query from the point the query is made
> untill the transaction is committed? or does the TupleTable go away as soon
> as query is finished executing?
It goes away as soon as the query finishes.
My answer above was mistaken --- plan nodes usually allocate slots in a
single TupleTable created (and destroyed) by execMain.c, rather than
each having their own TupleTable. But it's still a query-lifetime data
structure.
> I would think the TupleTable for that query is held untill the transaction
> is committed since lock on the tuple is endtill the end of transaction
You keep looking for nonexistent locks on tuples ...
The only resources represented by a TupleTable entry are memory for
a transient tuple (if we rewrote the system today, we'd forget that
function, since short-term memory contexts can do the job better)
or a buffer pin for a tuple that's sitting in a shared disk buffer.
There is no reason to hold a buffer pin beyond the time that the tuple
might actually be referenced by the query plan.
regards, tom lane
