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Help with an interesting Postgres question: Why isn't an Index Only Scan used on a partition accessed via the parent table?.
CREATE TABLE
CREATE INDEX
ERROR: index "uidx" column number 1 does not have default sorting behavior LINE 2: add constraint ucns ^ DETAIL: Cannot create a primary key or unique constraint using such an index.
ERROR: duplicate key value violates unique constraint "uidx" DETAIL: Key (val1)=(null) already exists.