Re: [GENERAL] Archiving data to another server using copy, psql withpipe

Il 05/04/2017 23:26, pinker ha scritto:
> Hi,
> I'm trying to write an archive manager which will be first copying data from
> tables with where clause and then, after successful load into second server
> - delete them.
> The simplest (and probably fastest) solution I came up with is to use copy:
> psql -h localhost postgres -c "copy (SELECT * FROM a WHERE time < now()) to
> stdout " | psql -h localhost  postgres   -c "copy b from stdin"
both  psql -h are on localhost. Is it a typo?
>
> I have made very simple test to check if I can be sure about "transactional"
> safety. It's not two phase commit of course but it's seems to throw an error
> if something went wrong and it's atomic (i assume). The test was:
>
> CREATE TABLE public.a
> (
>    id integer,
>    k01 numeric (3)
> );
>
> CREATE TABLE public.b
> (
>    id integer,
>    k01 numeric (1)
> );
>
> insert into a select n,n from generate_series(1,100) n;
>
> and then:
> psql -h localhost postgres -c "copy a to stdout "|psql -h localhost
> postgres   -c "copy b from stdin"
>
> so psql has thrown an error
... and what is the error?
> and no rows were inserted to the b table - so it
> seems to be ok.
>
> Is there maybe something I'm missing?
> Some specific condition when something could go wrong and make the process
> not atomic? (i don't care about data consistency in this particular case).
Without knowing OS and psql version of both servers, how they are
connected, or what error you get, it's hard for me to help you further.

Best regards
Moreno.
>
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>
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