plpgsql return column name and column stats as a table - plpgsql

Question

I am trying to use pgplpsql in a postgres database to:
- loop through all columns in a schema, and for every column that is double precision I want to return a table containing fields 'table name, column name, min value, max value, mean value, median value.
-So far I have managed to return the min, max, mean of these fields - but not in a table despite defining the table in the 'returns statement'.
Question:
How do I return a table properly
How do I include the column name and table name for the columns within this table? I have tried many things with a full range of error messages.
Becky
DROP FUNCTION household.numeric_stats(schemanm text);
CREATE OR REPLACE FUNCTION household.numeric_stats(schemanm text)
returns table(min double precision, max double precision, avg double precision)as $$
DECLARE
cname text;
tname text;
BEGIN
for cname,tname in SELECT column_name::text col,table_name::text tble FROM information_schema.columns
where table_schema = schemanm and data_type in ('double precision')
and table_name::text not in ('ap_household','derived_forest_income', 'derived_product_income','derivedproduct_income','view_income_overview_by_household')
LOOP
RAISE NOTICE 'cname is: % from %', cname, tname;
return query
execute format('select min(%I), max(%I), avg(%I) from %I.%I where %I != ''NaN''', cname, cname, cname, schemanm, tname, cname);
END;
$$
LANGUAGE plpgsql;

Answer 1

Would work like this:
CREATE OR REPLACE FUNCTION household.numeric_stats(schemanm text)
RETURNS TABLE(tname text, cname text
, min float8, max float8
, avg float8, median float8) AS
$func$
BEGIN
FOR tname, cname IN
SELECT table_name::text, column_name::text
FROM information_schema.columns
WHERE table_schema = schemanm
AND data_type = 'double precision'
AND table_name <> ALL ('{ap_household,derived_forest_income, derived_product_income,derivedproduct_income,view_income_overview_by_household}'::varchar[])
LOOP
-- RAISE NOTICE 'tname: %, cname: %', tname, cname;
RETURN QUERY EXECUTE format(
$f$SELECT $1, $2, min(%1$I), max(%1$I), avg(%1$I), median(%1$I)
FROM %2$I.%3$I
WHERE %1$I <> 'NaN'$f$, cname, schemanm, tname)
USING tname, cname;
END LOOP;
END
$func$ LANGUAGE plpgsql;
Call:
SELECT * FROM household.numeric_stats('myschema');
You need to create the median aggregate functions before you can use it. Instructions in the Postgres Wiki:
https://wiki.postgresql.org/wiki/Aggregate_Median