> I've been thinking about it a little more, and on the whole I like using
> SIGINT the best. Here's my reasoning:
> 1. SIGINT is not normally generated for non-interactive processes,
> so for the ordinary case of a backend running under the postmaster
> it wouldn't be generated by accident. (As you point out, the default
> signal from kill(1) is SIGTERM not SIGINT.)
> 2. The only case where it *would* be easy to direct SIGINT to a backend
> is in the case of a backend hand-invoked from the command line. In this
> case I think that having control-C do a Cancel rather than kill the
> process is a fine idea --- it is exactly parallel to the behavior that
> psql now offers. People will probably get used enough to psql's
> behavior that having an interactive backend work differently would be
> a bad idea.
> 3. SIGQUIT normally generates a coredump, and is one of the few
> non-error signals that do so. If we use it for the cancel signal we
> will eliminate the easiest, most standard way of externally forcing a
> backend to coredump. That seems like a loss of a useful debug tool.
> Also, in all Unix applications that I'm familiar with, SIGQUIT is a
> "more severe" signal than SIGINT --- one expects that an app may trap
> SIGINT and return keyboard control, but SIGQUIT is supposed to kill it.
> Inverting the severity of SIGINT and SIGQUIT for a pgsql backend doesn't
> sound like a good plan.
> So I think we should leave SIGTERM and SIGQUIT alone, and redefine
> SIGINT to perform a cancel.
All very good points. SIGINT is good.
> BTW, I realized that SIGHUP is not really free, it's what is used to
> return control from elog(ERROR) to the main loop. The code probably
> should refer to it as SIGHUP not signal "1".
> regards, tom lane
> PS: I've got these changes coded up, and am about to start testing.
Bruce Momjian | 830 Blythe Avenue
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