Re: [HACKERS] PATCH: enabling parallel execution for cursorsexplicitly (experimental) - Mailing list pgsql-hackers

From Craig Ringer
Subject Re: [HACKERS] PATCH: enabling parallel execution for cursorsexplicitly (experimental)
Date
Msg-id CAMsr+YEY+ozeDRPTLWMYW7MtLuBUD7AqS+FqjE9Hdz-hagpb4Q@mail.gmail.com
Whole thread Raw
In response to Re: [HACKERS] PATCH: enabling parallel execution for cursorsexplicitly (experimental)  (Robert Haas <robertmhaas@gmail.com>)
Responses Re: [HACKERS] PATCH: enabling parallel execution for cursorsexplicitly (experimental)  (Robert Haas <robertmhaas@gmail.com>)
List pgsql-hackers
On 2 November 2017 at 10:01, Robert Haas <robertmhaas@gmail.com> wrote:

> I think that still leaves a fair number of scenarios to consider, and
> the error handling by itself seems pretty thorny.  Plus it's kind of a
> weird mode and, like Craig, I'm not really sure what it gets you.
> Maybe if somebody has the use case where this would help, they should
> just do:
>
> CREATE TEMP TABLE x AS SELECT * FROM t2 WHERE ...;
> DECLARE x CURSOR FOR SELECT * FROM x;

That forces materialization, and I'm guessing part of Tomas's goal
here is to prevent the need to materialize into a temp table /
tuplestore / etc.

It's not clear to me why an unbounded portal fetch, using the tcp
socket windows and buffers for flow control, isn't sufficient.

Tomas, can you explain the use case a bit more?


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


-- 
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers

pgsql-hackers by date:

Previous
From: Robert Haas
Date:
Subject: Re: [HACKERS] Partition-wise aggregation/grouping
Next
From: Peter Eisentraut
Date:
Subject: Re: [HACKERS] Enhancements to passwordcheck