Re: Keeping temporary tables in shared buffers

On Thu, Jun 21, 2018 at 07:42:54AM +0530, Amit Kapila wrote:
> On Wed, Jun 20, 2018 at 8:47 PM, Bruce Momjian <bruce@momjian.us> wrote:
> > On Sat, Jun  2, 2018 at 05:18:17PM -0400, Asim Praveen wrote:
> >> Hi Amit
> >>
> >> On Mon, May 28, 2018 at 4:25 AM, Amit Kapila <amit.kapila16@gmail.com> wrote:
> >> >
> >> > This is one way, but I think there are other choices as well.  We can
> >> > identify and flush all the dirty (local) buffers for the relation
> >> > being accessed parallelly.  Now, once the parallel operation is
> >> > started, we won't allow performing any write operation on them.  It
> >>
> >> We talked about this in person in Ottawa and it was great meeting you!
> >>  To summarize, the above proposal to continue using local buffers for
> >> temp tables is a step forward, however, it enables only certain kinds
> >> of queries to be parallelized for temp tables.  E.g. queries changing
> >> a temp table in any way cannot be parallelized due to the restriction
> >> of no writes during parallel operation.
> >
> > Should this be a TODO item?
> >
> 
> +1.  I think we have not hammered out the design completely, but if
> somebody is willing to put effort, it is not an unsolvable problem.
> AFAIU, this thread is about parallelizing queries that refer temp
> tables, however, it is not clear from the title of this thread.

Seems it is already documented on the wiki:

    https://wiki.postgresql.org/wiki/Parallel_Query#What_Parts_of_a_Query_Can_Run_In_Parallel.3F

    o  Scans of plain tables may not appear below Gather if (1) they are
       temporary tables ...
       ----------------

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  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
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