在存储函数 Postgresql 中选择和更新

Question

我创建了一个用于获取数据的存储函数：

CREATE OR REPLACE FUNCTION sold_quantity()  
RETURNS TABLE(  
 invoiceid BIGINT,  
 itemid BIGINT,  
 sum_sold_quantity NUMERIC)  
AS $$  
BEGIN  
 RETURN QUERY SELECT  
 invoice_id as invoiceid, item_id as itemid, sum(sold_quantity) as  
 sum_sold_quantity  
 FROM  
 invoice_item  
 WHERE  
 status='sold'  
 GROUP BY  
 invoice_id, item_id;  
END; $$  

LANGUAGE 'plpgsql';  

如何存储这些数据并使用它来更新下表？

UPDATE invoice_item 
    SET sold_quantity = sum_sold_quantity 
where invoice_id=invoiceid 
  and item_id = itemid;

我们如何将这两个查询（选择和更新）合并到一个存储函数中并执行以获取具有上述三列的所有 500k 记录并批量更新（如 10 000 条记录）

Answer 1

可以直接在UPDATE语句中使用该函数

UPDATE invoice_item ii
    SET sold_quantity = sq.sum_sold_quantity 
from sold_quantity() as sq
where ii.invoice_id = sq.invoiceid 
  and ii.item_id = sq.itemid;

---

对于仅 500.000 行，我根本不会费心进行任何批处理。只需在一条语句中更新所有行。

事实上你并不需要一个函数来开始：

UPDATE invoice_item ii
    SET sold_quantity = sq.sum_sold_quantity 
from (
  select invoice_id as invoiceid, item_id as itemid, sum(sold_quantity) as  sum_sold_quantity  
  FROM  invoice_item  
  WHERE status='sold'  
  GROUP BY  invoice_id, item_id;  
) as sq
where ii.invoice_id = sq.invoiceid 
  and ii.item_id = sq.itemid;