On 30 June 2016 at 02:32, Andres Freund <and...@anarazel.de> wrote:

> Hi,
> On 2016-06-28 10:01:28 +0000, Rajeev rastogi wrote:
> > >3) Our 1-by-1 tuple flow in the executor has two major issues:
> >
> > Agreed, In order to tackle this IMHO, we should
> > 1. Makes the processing data-centric instead of operator centric.
> > 2. Instead of pulling each tuple from immediate operator, operator can
> push the tuple to its parent. It can be allowed to push until it sees any
> operator, which cannot be processed without result from other operator.
> > More details from another thread:
> >
> https://www.postgresql.org/message-id/bf2827dcce55594c8d7a8f7ffd3ab77159a9b...@szxeml521-mbs.china.huawei.com
> I doubt that that's going to be ok in the generic case (memory usage,
> materializing too much, "bushy plans", merge joins)

Yeah. You'd likely start landing up with Haskell-esque predictability of
memory use. Given how limited and flawed work_mem handling etc already is,
that doesn't sound like an appealing direction to go in. Not without a
bunch of infrastructure to manage queue sizes and force work into batches
to limit memory use, anyway.

 Craig Ringer                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services

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