Re: generic plans and "initial" pruning

Amit Langote <amitlangote09(at)gmail(dot)com> writes:
> The short of it is that the cached-plan-inval test in the
> delay_execution suite can never be made to work under
> CLOBBER_CACHE_ALWAYS. The test assumes that locks on partitions for a
> reused generic plan are not taken until InitPlan(). However, under
> CLOBBER_CACHE_ALWAYS, generic plans are never reused, so the test's
> assumption never holds.

Ugh.

> I see two possible ways to address this:

> 1. Find a way to disable the cached-plan-inval test in
> CLOBBER_CACHE_ALWAYS builds. However, I haven't found any other test
> that does this.

> 2. Remove the test altogether, though that might be too drastic.

Well, you could force matters with "set debug_discard_caches = 0"
within the test, but I think that's just a band-aid that would
not make the test fully stable. The point of CLOBBER_CACHE_ALWAYS
is to model random arrival of cache flush events, which is *always*
a possibility due to background activity (autovacuum for instance).

We do have a couple of other regression tests that rely on
"set debug_discard_caches = 0", and I've not seen many buildfarm
failures tracing to that, but I don't trust it a whole lot.

How badly do you want to keep this test case? It seems fairly
rickety to me, even without this particular concern.

regards, tom lane