Re: Interrupting long external library calls

On 16/05/12 11:39, Heikki Linnakangas wrote:

>> One of the issues we've been looking at with PostGIS is how to interrupt
>> long-running processing tasks in external libraries, particularly GEOS.
>> After a few tests here, it seems that even the existing SIGALRM handler
>> doesn't get called if statement_timeout is reached when in an external
>> library, e.g. with PostgreSQL 9.0/PostGIS 2.0 trunk/GEOS:
>
> If you interrupt an external library call, it might leave memory in an
> inconsistent state, or some other such thing. It's not generally safe to
> interrupt arbitrary 3rd party code.
>
> However, if you're absolutely positively sure that the library function
> can tolerate that, you can set "ImmediateInterruptOK = true" before
> calling it. See e.g PGSemaphoreLock() on how that's done before starting
> to sleep on a semapgore.

Hi Heikki,

Yes that appears to work fine on the surface - just testing now to
determine what state everything is left in when queries are aborted
prematurely.

Many thanks,

Mark.