Re: BUG #9198: psql -c 'SET; ...' not working

Re: Tom Lane 2014-02-12 <25094(dot)1392219652(at)sss(dot)pgh(dot)pa(dot)us>
> The reason this isn't a bug is that a -c command string is sent to the
> server as a single statement (PQexec call), and what "statement timeout"
> controls is the total time for the whole thing. The SET operation can't
> change the already-running timer for the current statement. It would
> affect the timeout for the next statement ... but there won't be one.
>
> Many people have complained that it's unintuitive that -c works this way
> rather than breaking up the string into multiple submissions the same way
> psql would do with normal input. We're afraid to change it for fear of
> breaking applications, though. If you want behavior more like psql's
> normal operation, consider
>
> echo "SET statement_timeout = '3s'; SELECT pg_sleep(2)" | psql

I think the docs don't really say that. The psql manpage says "single
transaction", but the problem here is rather "single command". I see
that "fixing" this would break the "one transaction" part, so it's
going to stay that way, but I'd propose something like this doc
update:

*** a/doc/src/sgml/ref/psql-ref.sgml
--- b/doc/src/sgml/ref/psql-ref.sgml
*************** PostgreSQL documentation
*** 100,106 ****
string to divide it into multiple transactions. This is
different from the behavior when the same string is fed to
<application>psql</application>'s standard input. Also, only
! the result of the last SQL command is returned.
</para>
</listitem>
</varlistentry>
--- 100,111 ----
string to divide it into multiple transactions. This is
different from the behavior when the same string is fed to
<application>psql</application>'s standard input. Also, only
! the result of the last SQL command is returned. <command>SET</>
! commands that modify statement behavior will be ineffective because
! they are part of the already running statement. Most notably,
! <literal>psql -c 'SET statement_timeout = 0; SELECT ...'</literal>
! will not work as expected. (Use <literal>echo '...' | psql</literal>
! as above instead.)
</para>
</listitem>
</varlistentry>

I'm actually unsure if there's more SETs that have this surprising
behavior, if statement_timeout is the only one, psql(1) should mention
that instead of what I wrote in the patch.

Mit freundlichen Grüßen,
Christoph Berg
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