如何在 Postgres 中使用 upsert

Question

I want to convert this code in Postgres to something shorter that will do the same. I read about upsert but I couldn't understand a good way to implement that on my code. What I wrote works fine, but I want to find a more elegant way to write it. Hope someone here can help me: This is the query:

CREATE OR REPLACE FUNCTION insert_table(
    in_guid    character varying,
    in_x_value character varying,
    in_y_value character varying
)
RETURNS TABLE(response boolean) LANGUAGE 'plpgsql'

DECLARE _id integer;

BEGIN
    -- guid exists and it's been 10 minutes from created_date:
    IF ((SELECT COUNT (*) FROM public.tbl_client_location WHERE guid = in_guid AND created_date < NOW() - INTERVAL '10 MINUTE') > 0) THEN
        RETURN QUERY (SELECT FALSE);
    
    -- guid exists but 10 minutes hasen't passed yet:
    ELSEIF ((SELECT COUNT (*) FROM public.tbl_client_location WHERE guid = in_guid) > 0) THEN
    
        UPDATE
            public.tbl_client_location
        SET
            x_value = in_x_value,
            y_value = in_y_value,
            updated_date = now()
        WHERE
            guid = in_guid;

        RETURN QUERY (SELECT TRUE);
    
    -- guid not exist:
    ELSE
       
        INSERT INTO public.tbl_client_location
            ( guid   , x_value   , y_value    )
        VALUES
            ( in_guid, in_x_value, in_y_value )
        RETURNING id INTO _id;  

        RETURN QUERY (SELECT TRUE);

    END IF;
END

Answer 1

This can indeed be a lot simpler :

CREATE OR REPLACE FUNCTION insert_table(in_guid text
                                      , in_x_value text
                                      , in_y_value text
                                      , OUT response bool)  -- ④
  -- RETURNS record  -- optional noise  -- ④
  LANGUAGE plpgsql AS  -- ①
$func$  -- ②
-- DECLARE
   -- _id integer;  -- what for?
BEGIN
   INSERT INTO tbl AS t
          (   guid,    x_value,    y_value)
   VALUES (in_guid, in_x_value, in_y_value)
   ON CONFLICT (guid) DO UPDATE  -- guid exists
   SET    (         x_value,          y_value, updated_date)
        = (EXCLUDED.x_value, EXCLUDED.y_value, now())  -- ⑤
   WHERE  t.created_date >= now() - interval '10 minutes'  -- ③ have not passed yet
   -- RETURNING id INTO _id  -- what for?
   ;
   response := FOUND;  -- ⑥
END
$func$;

Assuming guid is defined UNIQUE or PRIMARY KEY , and created_date is defined NOT NULL DEFAULT now() .

① Language name is an identifier - better without quotes.

② Quotes around function body were missing (invalid command). See:

• What are '$$' used for in PL/pgSQL

③ UPDATE only if 10 min have not passed yet. Keep in mind that timestamps are those from the beginning of the respective transactions. So keep transactions short and simple. See:

• Difference between now() and current_timestamp

④ A function with OUT parameter(s) and no RETURNS clause returns a single row ( record ) automatically. Your original was declared as set-returning function (0-n returned rows), which didn't make sense. See:

• Return multiple fields as a record in PostgreSQL with PL/pgSQL

⑤ It's generally better to use the special EXCLUDED row than to spell out values again. See:

• How could this UPSERT query be made shorter?

⑤ Also using short syntax for updating multiple columns. See:

• Update multiple columns that start with a specific string

⑥ To see whether a row was written use the special variable FOUND . Subtle difference: different from your original, you get true or false after the fact , saying that a row has actually been written (or not). In your original, the INSERT or UPDATE might still be skipped (without raising an exception) by a trigger or rule, and the function result would be misleading in this case. See:

• IS NOT NULL test for a record does not return TRUE when variable is set

Further reading:

• Postgres ON CONFLICT ON CONSTRAINT triggering errors in the error log
• How to use RETURNING with ON CONFLICT in PostgreSQL?

---

You might just run the single SQL statement instead, providing your values once :

INSERT INTO tbl AS t(guid, x_value,y_value)
VALUES ($in_guid, $in_x_value, $in_y_value)  -- your values here, once
ON CONFLICT (guid) DO UPDATE
SET    (x_value,y_value, updated_date)
     = (EXCLUDED.x_value, EXCLUDED.y_value, now())
WHERE  t.created_date >= now() - interval '10 minutes';

Answer 2

I finally solved it. I made another function that'll be called and checked if it's already exists and the time and then I can do upsert without any problems. That's what I did at the end:

CREATE OR REPLACE FUNCTION fnc_check_table(
    in_guid character varying)
    RETURNS TABLE(response boolean) 
    LANGUAGE 'plpgsql'

    COST 100
    VOLATILE 
    ROWS 1000
AS $BODY$
BEGIN
IF EXISTS (SELECT FROM tbl WHERE guid = in_guid AND created_date < NOW() - INTERVAL '10 MINUTE' ) THEN
RETURN QUERY (SELECT FALSE);
ELSEIF EXISTS (SELECT FROM tbl WHERE guid = in_guid AND created_date > NOW() - INTERVAL '10 MINUTE') THEN
RETURN QUERY (SELECT TRUE);
ELSE
RETURN QUERY (SELECT TRUE);
END IF;

END
$BODY$;



CREATE OR REPLACE FUNCTION fnc_insert_table(
    in_guid character varying,
    in_x_value character varying,
    in_y_value character varying)
    RETURNS TABLE(response boolean) 
    LANGUAGE 'plpgsql'

    COST 100
    VOLATILE 
    ROWS 1000
AS $BODY$
BEGIN
IF (fnc_check_table(in_guid)) THEN
    INSERT INTO tbl (guid, x_value, y_value)
    VALUES (in_guid,in_x_value,in_y_value)
    ON CONFLICT (guid)
    DO UPDATE SET x_value=in_x_value, y_value=in_y_value, updated_date=now();
    RETURN QUERY (SELECT TRUE);
ELSE
    RETURN QUERY (SELECT FALSE);
END IF;
END
$BODY$;