Re: [HACKERS] Autovacuum launcher occurs error when cancelled by SIGINT

On Fri, Jun 23, 2017 at 7:02 AM, Alvaro Herrera
<alvherre@2ndquadrant.com> wrote:
> Thomas Munro wrote:
>> I thought about this when designing the DSA API.  I couldn't think of
>> any good reason to provide an 'am-I-already-attached?' function
>> equivalent to dsm_find_mapping.  It seemed to me that the client code
>> shouldn't ever be in any doubt about whether it's attached, and that
>> wilfully or absent-mindedly throwing away dsa_area pointers and having
>> to ask for them again doesn't seem like a very good design.  I suspect
>> the same applies to dsm_find_mapping, and I don't see any callers in
>> the source tree or indeed anywhere on the internet (based on a quick
>> Google search).  But I could be missing something.

I don't think that's completely exact. dsm_attach() uses at its
duplicates dsm_find_mapping() to see if a segment is already attached.
So dsm_attach could be refactored to directly use dsm_find_mapping().

> I think such an API call is potentially useful for things like assertion
> checks, if nothing else.

Indeed, that's useful here as well.
-- 
Michael