Partial index where clause not filtering through

I have the following index:
street_range__street_locality_high_low_v btree (street_name_id,
    locality_id, addr_high_v, addr_low_v) WHERE (addr_high_v IS NOT NULL)

The query has a where clause like this:
        FROM street_range s, input i
        WHERE 1=1
            AND i.address_v IS NOT NULL

            AND s.locality_id = i.locality_id
            AND s.street_name_id = i.street_name_id

            AND s.addr_low_v <= i.address_v
            AND s.addr_high_v >= i.address_v

As-is, it won't use the index. i.address_v IS NOT NULL AND s.addr_high_v
 >= i.address_v should mandate that s.addr_high_v must be not-null, if
I'm remembering how nulls work correctly. (Actually, having any kind of
comparison on s.addr_high_v should mandate NOT NULL since NULL != NULL,
right?) Therefore the optimizer should be able to deduce that it can use
the index.

Adding AND s.addr_high_v IS NOT NULL to the where clause makes
everything work fine, so there is a work-around. Just seems like a minor
item to add to the TODO.
--
Jim C. Nasby (aka Decibel!)                    jim@nasby.net
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