Re: [HACKERS] pg_background contrib module proposal

On Mon, Dec 19, 2016 at 09:30:32PM +0500, Andrew Borodin wrote:
> 2016-12-19 4:21 GMT+05:00 David Fetter <david@fetter.org>:
> > Couldn't it sleep in increments smaller than a second?  Like maybe
> > milliseconds?  Also, it's probably cleaner (or at least more
> > comprehensible) to write something using format() and dollar quoting
> > than the line with the double 's.
> 
> Right. Here's version which waits for half a second. I do not see how
> to path doubles via dollar sign, pg_background_launch() gets a string
> as a parameter, it's not EXCEUTE USING.

I see.

I find the following a little easier to follow, and the sleeps still
work even when very short.

Best,
David.

CREATE TABLE input AS
SELECT x, row_number() OVER (ORDER BY x) n
FROM   generate_series(0,.000005,0.000001) x   ORDER BY x DESC;

CREATE TABLE output(place int,value float);

CREATE TABLE handles AS
SELECT pg_background_launch(   format($$       SELECT pg_sleep(%s);       INSERT INTO output VALUES (%s, %s)       $$,
    x, n, x   )
 
) h
FROM input;

--wait until everyone finishes
SELECT * FROM handles JOIN LATERAL pg_background_result(handles.h) AS (x TEXT) ON (true);

--output results
SELECT * FROM output ORDER BY place;

-- 
David Fetter <david(at)fetter(dot)org> http://fetter.org/
Phone: +1 415 235 3778  AIM: dfetter666  Yahoo!: dfetter
Skype: davidfetter      XMPP: david(dot)fetter(at)gmail(dot)com

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