合併多個結果表並對結果執行最終查詢

Question

我有一個返回表的函數，它將多個調用的輸出累加到另一個返回表的函數中。我想在返回結果之前對構建的表執行最終查詢。目前，我實現了這個爲兩個功能，一個積累和一個進行最後的查詢，這是醜陋：

CREATE OR REPLACE FUNCTION func_accu(LOCATION_ID INTEGER, SCHEMA_CUSTOMER TEXT) 
    RETURNS TABLE("networkid" integer, "count" bigint) AS $$ 
DECLARE 
GATEWAY_ID integer; 
BEGIN 
    FOR GATEWAY_ID IN 
     execute format(
      'SELECT id FROM %1$I.gateway WHERE location_id=%2$L' 
      , SCHEMA_CUSTOMER, LOCATION_ID) 
    LOOP 
     RETURN QUERY execute format(
      'SELECT * FROM get_available_networks_gw(%1$L, %2$L)' 
      , GATEWAY_ID, SCHEMA_CUSTOMER); 
    END LOOP; 
END; 
$$ LANGUAGE plpgsql; 


CREATE OR REPLACE FUNCTION func_query(LOCATION_ID INTEGER, SCHEMA_CUSTOMER TEXT) 
    RETURNS TABLE("networkid" integer, "count" bigint) AS $$ 
DECLARE 
BEGIN 
    RETURN QUERY execute format(' 
     SELECT networkid, max(count) FROM func_accu(%2$L, %1$L) GROUP BY networkid;' 
    , SCHEMA_CUSTOMER, LOCATION_ID); 
END; 
$$ LANGUAGE plpgsql; 

這怎麼能在單一功能做，優雅？

Answer 1

兩個函數簡化和合並，在USING clause也供給值參數：

CREATE OR REPLACE FUNCTION pg_temp.func_accu(_location_id integer, schema_customer text) 
    RETURNS TABLE(networkid integer, count bigint) AS 
$func$ 
BEGIN 
    RETURN QUERY EXECUTE format(' 
     SELECT f.networkid, max(f.ct) 
     FROM %I.gateway g 
      , get_available_networks_gw(g.id, $1) f(networkid, ct) 
     WHERE g.location_id = $2 
     GROUP BY 1' 
    , _schema_customer) 
    USING _schema_customer, _location_id; 
END 
$func$ LANGUAGE plpgsql; 

呼叫：

SELECT * FROM func_accu(123, 'my_schema'); 

相關：

• Dynamically access column value in record

我爲函數返回的列使用別名（f(networkid, ct)），因爲您沒有公開返回類型get_available_networks_gw()。您可以直接使用返回類型的列名稱。

FROM子句中的逗號（,）是CROSS JOIN LATERAL ...的簡短語法。需要Postgres 9.3或更高版本。

• What is the difference between LATERAL and a subquery in PostgreSQL?

或者你可以運行此查詢，而不是功能：

SELECT f.networkid, max(f.ct) 
FROM myschema.gateway g, get_available_networks_gw(g.id, 'my_schema') f(networkid, ct) 
WHERE g.location_id = $2 
GROUP BY 1;