Re: [HACKERS] Re: new set of psql patches for loading (saving) datafrom (to) text, binary files - Mailing list pgsql-hackers

From Pavel Stehule
Subject Re: [HACKERS] Re: new set of psql patches for loading (saving) datafrom (to) text, binary files
Date
Msg-id CAFj8pRBXEvs4XUe9Ab54tq4q32mGfh=sLE99h-fdCOzwcNxbZw@mail.gmail.com
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In response to Re: [HACKERS] Re: new set of psql patches for loading (saving) datafrom (to) text, binary files  (Stephen Frost <sfrost@snowman.net>)
List pgsql-hackers


2017-04-06 14:47 GMT+02:00 Stephen Frost <sfrost@snowman.net>:
Greetings,

* Pavel Stehule (pavel.stehule@gmail.com) wrote:
> 2017-04-06 3:34 GMT+02:00 Stephen Frost <sfrost@snowman.net>:
> > Having the template not require the row/column place-holders included
> > strikes me as more likely to be confusing.  My initial thinking around
> > this was that users who actually want independent files would simply
> > issue independent queries, while users who want to take a bunch of int4
> > columns and dump them into a single binary file would be able to do so
> > easily.
> >
> > I'm not against adding the ability for a single query result to be saved
> > into independent files, but it strikes me as feature creep on this basic
> > capability.  Further, I don't see any particular reason why splitting up
> > the output from a query into multiple files is only relevant for binary
> > data.
>
> The files can be simply joined together outside psql

Just as multiple queries could be done to have the results put into
independent files.

> Personally I prefer relation type: single field, single file  in special g
> command - because I can simply off all formatting and result should be
> correct every time.

Not sure why you think there would be a formatting issue or why the
result might not be 'correct'.

> Stephen, have you some use case for your request?

The initial patch forced a single value result.  Including such a
restriction doesn't seem necessary to me.  As for use-case, I've
certainly written code to work with binary-result data from PG
previously and it seems entirely reasonable that someone might wish to
pull data into a file with psql and then process it.  I've been
wondering if we should consider how binary-mode COPY works, but that
format ends up being pretty inefficient due to the repeated 32-bit
length value for every field.

My initial reaction was primairly that I didn't see value in the
somewhat arbitrary restriction being imposed on usage of this.

ok.

It is hard to design any solution - because there are not any intersection on this basic simple things.

Regards

Pavel
 

Thanks!

Stephen

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