| From: | Jeff Davis <pgsql(at)j-davis(dot)com> |
|---|---|
| To: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> |
| Cc: | Daniel Farina <drfarina(at)gmail(dot)com>, Hannu Krosing <hannu(at)krosing(dot)net>, Greg Smith <greg(at)2ndquadrant(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Daniel Farina <dfarina(at)truviso(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: [PATCH 4/4] Add tests to dblink covering use of COPY TO FUNCTION |
| Date: | 2009-11-26 07:18:55 |
| Message-ID: | 1259219935.19289.505.camel@jdavis |
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| Lists: | pgsql-hackers |
On Thu, 2009-11-26 at 05:01 +0100, Pavel Stehule wrote:
> It working like:
>
> 1. EXECUTE SELECT 0 FROM generate_series(1,...);
> 2. STORE RESULT TO TABLE zero;
> 3. EXECUTE SELECT 1/i FROM zero;
> 4. STORE RESULT TO TABLE tmp;
>
> Problem is in seq execution. Result is stored to destination after
> execution - so any materialisation is necessary,
>
My example showed that steps 3 and 4 are not executed sequentially, but
are executed together. If 3 was executed entirely before 4, then the
statement:
insert into tmp select 1/i from zero;
would have to read the whole table "zero" before an error is
encountered.
However, the statement errors immediately, showing that steps 3 and 4
are pipelined.
Regards,
Jeff Davis
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