Re: TRIM_ARRAY

The following review has been posted through the commitfest application:
make installcheck-world: tested, passed
Implements feature: tested, passed
Spec compliant: tested, failed
Documentation: tested, failed

This basically does what it says, and the code looks good. The
documentation is out of alphabetical order (trim_array should appear
under cardinality rather than over)) but good otherwise. I was able to
"break" the function with an untyped null in psql:

select trim_array(null, 2);
ERROR: could not determine polymorphic type because input has type unknown

I don't know whether there are any circumstances other than manual entry
in psql where this could happen, since column values and variables will
always be typed. I don't have access to the standard, but DB2's docs[1]
note "if any argument is null, the result is the null value", so an
up-front null check might be preferable to a slightly arcane user-facing
error, even if it's a silly invocation of a silly function :)

[1] https://www.ibm.com/support/knowledgecenter/en/SSEPEK_12.0.0/sqlref/src/tpc/db2z_bif_trimarray.html

The new status of this patch is: Waiting on Author