将查询结果保存到列数未知的临时 table

Question

我正在尝试在 plpgsql 中创建以下函数：

CREATE OR REPLACE FUNCTION pg_temp.select_all(query text)
RETURNS VOID AS $$
DECLARE
    schemasT RECORD;
BEGIN
    FOR schemasT IN (
        SELECT schema_name
        FROM information_schema.schemata
        WHERE schema_name IN (
            SELECT login 
            FROM cdu.nc_tenant
        )
    ) LOOP
        SET SEARCH PATH TO schemasT;
    
        EXECUTE query INTO something;
    END LOOP;
END; $$
LANGUAGE plpgsql;

因此，传递给该函数的任何查询都会运行到所有可用的模式中，并 return 查询的结果。使用该函数将是这样的：

pg_temp.select_all('SELECT count(1) FROM sku')

会 return:

Schema	count
Schema1	58
Schema2	42

另一个例子是：

pg_temp.select_all('SELECT * FROM cdu.nc_tenant_variables where variable = ''theme''')

会 return:

Schema	variable	value
Schema1	theme	dark
Schema2	theme	light

为什么？

有时我需要跨模式查询内容，我正在寻找更好的方法来执行此操作而不是执行以下操作：

SELECT 'schema1' AS schema, count(1) FROM schema1.sku
UNION ALL
SELECT 'schema2' AS schema, count(1) FROM schema2.sku
UNION ALL
SELECT 'schema3' AS schema, count(1) FROM schema3.sku;

Answer 1

我以某种方式让它工作，但它 returns 一个 JSON 对象而不是一个普通的 table:

DROP FUNCTION pg_temp.select_all;
CREATE OR REPLACE FUNCTION pg_temp.select_all(query TEXT, whole int DEFAULT 0)
RETURNS table (j json) AS $$
DECLARE
    schemasT RECORD;
    counter int := 1;
    test RECORD;
BEGIN
    DROP TABLE IF EXISTS resultquery;

    FOR schemasT IN (
        SELECT schema_name
        FROM information_schema.schemata
        WHERE schema_name IN (
            SELECT login 
            FROM cdu.nc_tenant
        )
    ) LOOP
        EXECUTE format('SET SEARCH_PATH TO %I', schemasT.schema_name);
        
        IF counter = 1 THEN
            EXECUTE 'CREATE TEMP TABLE resultquery AS '|| query;
            ALTER TABLE pg_temp.resultquery ADD COLUMN tenant varchar;
            TRUNCATE TABLE resultquery;
        END IF;
    
        DROP TABLE IF EXISTS temptemp;
        EXECUTE 'CREATE TEMP TABLE temptemp AS '|| query;
        ALTER TABLE pg_temp.temptemp ADD COLUMN tenant varchar;
        
        UPDATE pg_temp.temptemp SET tenant = schemasT.schema_name;
        EXECUTE 'INSERT INTO pg_temp.resultquery SELECT * FROM pg_temp.temptemp';
    
        counter := counter + 1;
    END LOOP;
    
    IF whole = 0 THEN
        RETURN QUERY  SELECT to_json(a) FROM (SELECT * FROM pg_temp.resultquery) a;
    ELSE 
        RETURN QUERY  SELECT json_agg(a) FROM (SELECT * FROM pg_temp.resultquery) a;
    END IF;
END; $$
LANGUAGE plpgsql;

使用函数：

SELECT pg_temp.select_all('select count(1) from sku', 1);

Returns一行JSON对象

将查询结果保存到列数未知的临时 table

Saving a query result into a temp table with unknown number of columns

postgresql

plpgsql