Error in 8.0 rc5 with repeat calls to array operator

Developers,

I'm finding an issue I thought was fixed with RC2, which is affecting my
ability to use arrays in RC5:

Summary: Fast repeated calls to INT[] = INT[] operator causes error
Severity: Query Failure
Version: 8.0.0rc5, previous builds of 8.0.0
Platform: Gentoo Linux
Description:

The following comparison works fine normally:
template1=# select '{}'::INT[] = '{}'::INT[];
?column?
----------
t
(1 row)

However, we're found that if you run thousands of empty array comparisons in a
few seconds/minutes, eventually the empty array comparison breaks, and you
get:
ERROR: cache lookup failed for function 0

Thereafter, *any* attempt to compare arrays gets:
dm=# select '{}'::INT[] = '{}'::INT[];
ERROR: cache lookup failed for function 0

I'm working on a repeatable test case and seeing whether vacuum and/or restart
affects this, but since we're 24 hours from wrap, I thought I should raise
this issue ASAP.

--
--Josh

Josh Berkus
Aglio Database Solutions
San Francisco