Re: psql COPY vs. ON_ERROR_ROLLBACK, multi-command strings

Excerpts from Noah Misch's message of jue mar 08 12:11:37 -0300 2012:
>
> On Wed, Mar 07, 2012 at 04:57:12PM -0500, Robert Haas wrote:

> > As a side note, the documentation for PQexec() is misleading about
> > what will happen if COPY is present in a multi-command string. It
> > says: "Note however that the returned PGresult structure describes
> > only the result of the last command executed from the string. Should
> > one of the commands fail, processing of the string stops with it and
> > the returned PGresult describes the error condition. It does not
> > explain that it also stops if it hits a COPY. I had to read the
> > source code for libpq to understand why this psql logic was coded the
> > way it is.
>
> Agreed; I went through a similar process. Awhile after reading the code, I
> found the behavior documented in section "Functions Associated with the COPY
> Command":
>
> If a COPY command is issued via PQexec in a string that could contain
> additional commands, the application must continue fetching results via
> PQgetResult after completing the COPY sequence. Only when PQgetResult
> returns NULL is it certain that the PQexec command string is done and it is
> safe to issue more commands.
>
> I'm not quite sure what revision would help most here -- a cross reference,
> moving that content, duplicating that content. Offhand, I'm inclined to move
> it to the PQexec() documentation with some kind of reference back from its
> original location. Thoughts?

I would vote for moving it and adding a reference in the COPY functions
section. That way, the PQexec doc is complete by itself without having
to duplicate anything.

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Álvaro Herrera <alvherre(at)commandprompt(dot)com>
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