Re: ON_ERROR_EXIT and interactive mode (or, how to force interactive mode off)

[Tim Kane <tim.kane@xxxxxxxxx>]

Thanks Chris. I didn’t realise psycopg2 had a COPY interface, that’s quite handy. I’ll have a play, cheers.

Tim

From: Chris Curvey <chris@xxxxxxxxxxxxxxx>
Reply-To: <chris@xxxxxxxxxxxxxxx>
Date: Friday, 27 December 2013 21:18
To: Tim Kane <tim.kane@xxxxxxxxx>
Cc: pgsql-general General <pgsql-general@xxxxxxxxxxxxxx>
Subject: Re: ON_ERROR_EXIT and interactive mode (or, how to force interactive mode off)

On Fri, Dec 27, 2013 at 7:30 AM, Tim Kane <tim.kane@xxxxxxxxx> wrote:

HI all,

I have a fairly complex python script which calls a number of ‘psql’ sessions via a subprocess to perform bulk load operations.

The bulk loads are generated on the fly, and are written directly to the stdin of the subprocess.

I would like to rely on the _ON_ERROR_STOP_=1 functionality to force the process to exit with an error code – however, psql rightly believes the process it is operating under is an interactive one – since it is receiving its input from stdin.

For performance (and disk) reasons, I’d rather not have to rely on writing my input to a file, before passing it to psql with –f

This part of the man page gave me hope…

-f filename
--file filename

Use the file filename as the source of commands instead of reading commands interactively. After the file is processed, psql terminates. This is in many ways equivalent to the internal command \i.

If filename is - (hyphen), then standard input is read.

Using this option is subtly different from writing psql < filename. In general, both will do what you expect, but using -f enables some nice features such as error messages with line numbers. There is also a slight chance that using this option will reduce the start-up overhead. On the other hand, the variant using the shell's input redirection is (in theory) guaranteed to yield exactly the same output that you would have gotten had you entered everything by hand.

Eg:

psql –v _ON_ERROR_STOP_=1 –f - 

But it seems this is still understood by psql to be an interactive session, and fails to exit the process on an error.

Is there any way to force psql to read from stdin, in a non-interactive manner?  (that is, to ensure it exits the process on an error condition?)

Thanks for any advice

Tim

I'm afraid I can't answer your question directly (see my sig), but if you're already using Python to create the files, would you be better off using psycopg2's COPY interfaces?  If use just connect directly from Python to Postgres, I would think that your success and error handling would be much simpler.

http://initd.org/psycopg/docs/usage.html#using-copy-to-and-copy-from

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