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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?.
select mycol, split_part(mycol, '^', 1)
from (values ('JOHN^DOE'), ('BILLY^SMITH'), ('FIRL^GREGOIRE'), ('NOEL^JOHN')) as t(mycol)
| mycol | split_part |
|---|---|
| JOHN^DOE | JOHN |
| BILLY^SMITH | BILLY |
| FIRL^GREGOIRE | FIRL |
| NOEL^JOHN | NOEL |