Melakukan pembaruan besar menggunakan banyak tabel di PostgreSQL

Kueri ini harus menghasilkan hasil yang sama, tetapi menghindari CASE

-- EXPLAIN ANALYZE
UPDATE table_a a
SET rebuilding_costs = drie.rebuilding_costs
FROM (
        SELECT COALESCE(b.address, c.address, d.address) AS address
        , COALESCE(b.rebuilding_costs, c.rebuilding_costs,  d.rebuilding_costs)
            AS rebuilding_costs
        FROM table_b b
        FULL OUTER JOIN table_c c ON c.address = b.address
                AND  c.rebuilding_costs BETWEEN 200001 AND 400000
        FULL OUTER JOIN table_D d ON d.address = b.address
                AND  d.rebuilding_costs BETWEEN 400001 AND 600000
        WHERE b.rebuilding_costs BETWEEN 100001 AND 200000
        ) drie
WHERE a.address = drie.address
AND a.rebuilding_costs <> drie.rebuilding_costs -- Avoid useless updates
        ;

PEMBARUAN:Pendekatan serupa, berdasarkan rangkaian CTE yang dirantai:

-- --------------------------------
EXPLAIN ANALYZE
WITH cte_b AS (
        SELECT b.address,  b.rebuilding_costs
        FROM table_b b
        WHERE b.rebuilding_costs BETWEEN 100001 AND 200000
        )
,       cte_c AS (
        SELECT c.address , c.rebuilding_costs
        FROM table_c c
        WHERE  c.rebuilding_costs BETWEEN 200001 AND 400000
        AND NOT EXISTS (SELECT * FROM cte_b WHERE cte_b.address = c.address)
        )
,       cte_d AS (
        SELECT d.address , d.rebuilding_costs
        FROM table_d d
        WHERE  d.rebuilding_costs BETWEEN 400001 AND 600000
        AND NOT EXISTS (SELECT * FROM cte_b WHERE cte_b.address = d.address)
        AND NOT EXISTS (SELECT * FROM cte_c WHERE cte_c.address = d.address)
        )
,       cte_bcd AS (
        SELECT           cte_b.address,  cte_b.rebuilding_costs FROM cte_b
        UNION ALL SELECT cte_c.address,  cte_c.rebuilding_costs FROM cte_c
        UNION ALL SELECT cte_d.address,  cte_d.rebuilding_costs FROM cte_d
        )
UPDATE table_a a
SET rebuilding_costs = cte_bcd.rebuilding_costs
FROM cte_bcd
WHERE a.address = cte_bcd.address
-- avoid useless updates this way:
AND a.rebuilding_costs <> cte_bcd.rebuilding_costs
-- ,or this way:
-- AND cte_bcd.rebuilding_costs IS DISTINCT FROM a.rebuilding_costs
   ;

UPDATE2:CTE bisa lambat, karena bertindak sebagai penghalang pengoptimalan. Cara cepat &kotor adalah dengan menulis ulang tem sebagai TAMPILAN (sementara), dan merujuk ke ini sebagai gantinya. Ini memungkinkan pengoptimal untuk mengacak berbagai bagian kueri ke dalam dan keluar dari subkueri, dan bahkan menggabungkan dan menggunakan kembali ini.

CREATE TEMP VIEW cte_b AS (
        SELECT b.address,  b.rebuilding_costs
        FROM table_b b
        WHERE b.rebuilding_costs BETWEEN 100001 AND 200000
        );
CREATE TEMP VIEW        cte_c AS (
        SELECT c.address , c.rebuilding_costs
        FROM table_c c
        WHERE  c.rebuilding_costs BETWEEN 200001 AND 400000
        AND NOT EXISTS (SELECT * FROM cte_b WHERE cte_b.address = c.address)
        );
CREATE TEMP VIEW        cte_d AS (
        SELECT d.address , d.rebuilding_costs
        FROM table_d d
        WHERE  d.rebuilding_costs BETWEEN 400001 AND 600000
        AND NOT EXISTS (SELECT * FROM cte_b WHERE cte_b.address = d.address)
        AND NOT EXISTS (SELECT * FROM cte_c WHERE cte_c.address = d.address)
        );
CREATE TEMP VIEW        cte_bcd AS (
        SELECT           cte_b.address,  cte_b.rebuilding_costs FROM cte_b
        UNION ALL SELECT cte_c.address,  cte_c.rebuilding_costs FROM cte_c
        UNION ALL SELECT cte_d.address,  cte_d.rebuilding_costs FROM cte_d
        );
EXPLAIN -- ANALYZE
UPDATE table_a a
SET rebuilding_costs = cte_bcd.rebuilding_costs
FROM cte_bcd
WHERE a.address = cte_bcd.address
AND a.rebuilding_costs <> cte_bcd.rebuilding_costs -- avoid useless updates
-- AND a.address < 100000
        ;