"malformed array literal" error in PL/pgSQL - sql

Question

I got an error in PL/pgSQL:
"ERROR: malformed array literal: "2019-11-22 09:18:07.248537" DETAIL:
Array value must start with "{" or dimension information. CONTEXT:
PL/pgSQL function chargelengtth() line 11 at FOR over SELECT rows"
CREATE OR REPLACE FUNCTION chargelengtth() RETURNS text AS
$$
DECLARE chargetime integer;
DECLARE othertime integer;
DECLARE total integer;
DECLARE charge_length text[];
DECLARE chargestatus text;
DECLARE otherstatus text;
BEGIN
total := 0;
chargetime := 0;
FOR charge_length IN
SELECT * FROM table_name
LOOP
RAISE NOTICE 'Stuff: %', charge_length;
IF(charge_length[diagnostic] = 'Charging' AND chargetime = 0) THEN
chargetime := extract(epoch from charge_length[time]);
END IF;
IF(charge_length[diagnostic] != 'Charging') THEN
othertime := extract(epoch from charge_length[time]);
total := total + (othertime - chargetime);
chargetime := 0;
END IF;
END LOOP;
RETURN to_char(total * interval '1 sec','HH24h MIm');
END$$ LANGUAGE plpgsql;
SELECT * FROM chargelengtth()`
can you please share your knowledge to resolve this issue.

Answer 1

As documented in the manual you need to use a record variable when you want to loop over a SELECT statement:
CREATE OR REPLACE FUNCTION chargelengtth()
RETURNS text AS
$$
DECLARE
chargetime integer;
othertime integer;
total integer;
chargestatus text;
otherstatus text;
l_row record; --<< here
BEGIN
total := 0;
chargetime := 0;
FOR l_row IN SELECT * FROM table_name
LOOP
RAISE NOTICE 'Stuff: %', l_row;
IF (l_row.diagnostic = 'Charging' AND chargetime = 0) THEN
chargetime := extract(epoch from l_row.time);
END IF;
IF (l_row.diagnostic != 'Charging') THEN
othertime := extract(epoch from l_row.time);
total := total + (othertime - chargetime);
chargetime := 0;
END IF;
END LOOP;
RETURN to_char(total * interval '1 sec','HH24h MIm');
END$$ LANGUAGE plpgsql;
SELECT chargelengtth()
As far as I can tell, you can replace this with a single SELECT statement. Assuming the time column is a timestamp, I think the following is equivalent to what you are doing (except for the formatting of the interval at the end):
with ct (chargetime) as (
select time
from table_name
where diagnostic = 'Charging'
limit 1
)
select sum(t.time - ct.chargetime)
from the_table t
cross join ct
where t.diagnostic <> 'Charging'
The retrieval of the chargetime is a bit confusing as you seem to rely on some order of the rows, yet your query has no order by. The limit 1 without an order by does essentially the same, but if you want reproducible results you should really specify an order by (also for your FOR loop statement)