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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?.
WITH yourTable AS (
SELECT 1 AS PRODUCT, 'A' AS PRODUCT_TYPE, 20 AS PRICE UNION ALL
SELECT 2, 'A', 20 UNION ALL
SELECT 3, 'A', 30 UNION ALL
SELECT 4, 'B', 30 UNION ALL
SELECT 5, 'C', 30 UNION ALL
SELECT 6, 'C', 40
)
SELECT
PRODUCT,
PRODUCT_TYPE,
PRICE,
1.0 * PRICE / SUM(PRICE) OVER (PARTITION BY PRODUCT_TYPE) AS WEIGHT
FROM yourTable;
| product | product_type | price | weight |
|---|---|---|---|
| 1 | A | 20 | 0.28571428571428571429 |
| 2 | A | 20 | 0.28571428571428571429 |
| 3 | A | 30 | 0.42857142857142857143 |
| 4 | B | 30 | 1.00000000000000000000 |
| 5 | C | 30 | 0.42857142857142857143 |
| 6 | C | 40 | 0.57142857142857142857 |