Re: persistent portals/cursors (between transactions)

Bruce Momjian wrote:
> Tom Lane wrote:
> > Bruce Momjian <pgman@candle.pha.pa.us> writes:
> > >> I forgot to mention that I'd like to implement a cross
> > >> transaction insensitive(and read-only) cursors which
> > >> any proper dbms seems to have the functionality.
> >
> > > That is a good idea, especially read-only, that will not require any
> > > locks.
> >
> > If it's not holding any locks, I can guarantee you it's not insensitive.
> > Consider VACUUM, or even DROP TABLE.
>
> I assumed it would be an in-memory copy of the cursor, like a portal
> that doesn't go away on transaction exit.

    Ever realized what a portal is? So far it's a query for which
    ExecutorStart() has been called, just sitting there,  waiting
    for subsequent ExecutorRun() calls.

    How  such a thing can live outside of any transaction context
    isn't totally clear to me, even if I have to admit that I see
    by  now  the  desire for cross transaction cursors. It's just
    these lil' details like "how does the  portal  maintain  it's
    snapshot  POV  after  the  transaction  creating  it  is long
    gone?", that make me nervous.


Jan

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