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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 t as
select 1 as cust_id, '2019-01-01'::date as startd, '2019-12-10'::date as endd, 50.00 as subs_price_p_month union all
select 1 as cust_id, '2020-02-03'::date as startd, '2020-08-05'::date as endd, 39.99 as subs_price_p_month union all
select 2 as cust_id, '2019-12-11'::date as startd, '2020-11-08'::date as endd, 29.99 as subs_price_p_month
3 rows affected
select t.cust_id, yyyymm, t.subs_price_p_month
from t cross join lateral
generate_series( date_trunc('month', startd),
date_trunc('month', endd),
interval '1 month'
) gs(yyyymm)
| cust_id | yyyymm | subs_price_p_month |
|---|---|---|
| 1 | 2019-01-01 00:00:00+00 | 50.00 |
| 1 | 2019-02-01 00:00:00+00 | 50.00 |
| 1 | 2019-03-01 00:00:00+00 | 50.00 |
| 1 | 2019-04-01 00:00:00+01 | 50.00 |
| 1 | 2019-05-01 00:00:00+01 | 50.00 |
| 1 | 2019-06-01 00:00:00+01 | 50.00 |
| 1 | 2019-07-01 00:00:00+01 | 50.00 |
| 1 | 2019-08-01 00:00:00+01 | 50.00 |
| 1 | 2019-09-01 00:00:00+01 | 50.00 |
| 1 | 2019-10-01 00:00:00+01 | 50.00 |
| 1 | 2019-11-01 00:00:00+00 | 50.00 |
| 1 | 2019-12-01 00:00:00+00 | 50.00 |
| 1 | 2020-02-01 00:00:00+00 | 39.99 |
| 1 | 2020-03-01 00:00:00+00 | 39.99 |
| 1 | 2020-04-01 00:00:00+01 | 39.99 |
| 1 | 2020-05-01 00:00:00+01 | 39.99 |
| 1 | 2020-06-01 00:00:00+01 | 39.99 |
| 1 | 2020-07-01 00:00:00+01 | 39.99 |
| 1 | 2020-08-01 00:00:00+01 | 39.99 |
| 2 | 2019-12-01 00:00:00+00 | 29.99 |
| 2 | 2020-01-01 00:00:00+00 | 29.99 |
| 2 | 2020-02-01 00:00:00+00 | 29.99 |
| 2 | 2020-03-01 00:00:00+00 | 29.99 |
| 2 | 2020-04-01 00:00:00+01 | 29.99 |
| 2 | 2020-05-01 00:00:00+01 | 29.99 |
| 2 | 2020-06-01 00:00:00+01 | 29.99 |
| 2 | 2020-07-01 00:00:00+01 | 29.99 |
| 2 | 2020-08-01 00:00:00+01 | 29.99 |
| 2 | 2020-09-01 00:00:00+01 | 29.99 |
| 2 | 2020-10-01 00:00:00+01 | 29.99 |
| 2 | 2020-11-01 00:00:00+00 | 29.99 |