I am trying to call a function returning all columns of an existing table + some unrelated additional ones and retrieve the returned data using the following syntax:
select *
from test_func(...)
as (a_table my_table_name, rows_count numeric);
The function has the following format:
CREATE OR REPLACE FUNCTION public.test_func(...)
RETURNS SETOF record
LANGUAGE plpgsql
AS $function$
DECLARE
_sql VARCHAR;
begin
_sql := 'SELECT mtn.*, count(*) over() as rows_count
from public.my_table_name mtn
... inner joins and other stuff';
return query
execute _sql using ..._sql params...;
END;
$function$
;
However, it doesn't work. The error I receive:
ERROR: structure of query does not match function result type
Detail: Returned type numeric does not match expected type "my_table_name" in column 1.
If the query in your function should return a my_table_name (a “whole-row reference), you should write it like
SELECT mtn, count(*) OVER () ...
Related
Postgresql 12. Want a function to return query by calling another function but don't know how to call.
create or replace function getFromA()
returns table(_id bigint, _name varchar) as $$
begin
RETURN QUERY SELECT id, name from groups;
end; $$ language plpgsql;
create or replace function getFromB()
returns table(_id bigint, _name varchar) as $$
begin
return query select getFromA();
end; $$ language plpgsql;
select getFromB();
gets error:
SQL Error [42804]: ERROR: structure of query does not match function result type
Detail: Returned type record does not match expected type bigint in column 1.
Where: PL/pgSQL function getfromb() line 3 at RETURN QUERY
How to fix this?
The problem is in getFromB():
return query select getFromA();
Unlike some other databases, Postgres allows set-returning functions directly in the select clause. This works, but can be tricky: this returns a set, hence not the expected structure.
You would need to select ... from getFromA() instead: this way it returns the proper data structure.
create or replace function getFromB()
returns table(_id bigint, _name varchar) as $$
begin
return query select * from getFromA();
end; $$ language plpgsql;
Demo on DB Fiddle
I have a plpgsql function which act as a wrapper around several other functions, all of which are set returning functions of different data types. Through this function, I am trying to get a generic set returning function which can return set of any data type. The data type of record is decided based on the input table name and column name.
Here is the code snippet:
create function cs_get(tablename text, colname text) returns setof record as $$
declare
type_name text;
ctype text;
loadfunc text;
result record;
begin
select data_type into type_name from information_schema.columns where table_name = tablename and column_name = colname;
if type_name is null then
raise exception 'Table % doesnot exist or does not have attribute % ',tablename, colname;
end if;
ctype := cs_get_ctype(type_name);
loadfunc := 'select * from cs_get_'||ctype||'('''||tablename||''','''||colname||''')';
for result in execute loadfunc loop
return next result;
end loop;
return;
end; $$ language plpgsql;
Suppose the column is of type integer (corresponding c type is int64), loadfunc would be
select * from cs_get_int64(tablename, colname)
cs_get_int64 is a set-returning function defined in a C library which returns values of type int64.
However, this gives an error saying
ERROR: a column definition list is required for functions returning "record" at character 15
The easiest way to achieve this is to return a setof text for every data type. But that of course is not a clean way to do this. I have tried replacing loadFunc with
select cs_get_int64::integer from cs_get_int64(tablename, colname)
which is required to use records. But, this did not help.
My question now is:
Is it possible to create such a generic set returning function? If yes, how?
The answer is yes. But it's not trivial.
As long as you return anonymous records (returns setof record) a column definition list is required for the returned record to work with it in SQL. Pretty much what the error message says.
There is a (limited) way around this with polymorphic types:
CREATE OR REPLACE FUNCTION cs_get(_tbl_type anyelement, _colname text)
RETURNS SETOF anyelement AS
...
Detailed explanation int this related answer (climax in the last chapter!):
Refactor a PL/pgSQL function to return the output of various SELECT queries
I am trying to create a function that returns a SELECTed resultset.
When I call my postgres function like this select * from tst_dates_func() I get an error as shown below:
ERROR: query has no destination for result data
HINT: If you want to discard the results of a SELECT, use PERFORM instead.
CONTEXT: PL/pgSQL function "tst_dates_func" line 3 at SQL statement
********** Error **********
ERROR: query has no destination for result data
SQL state: 42601
Hint: If you want to discard the results of a SELECT, use PERFORM instead.
Context: PL/pgSQL function "tst_dates_func" line 3 at SQL statement
Here is the function I created:
CREATE OR REPLACE FUNCTION tst_dates_func()
RETURNS TABLE( date_value date, date_id int, date_desc varchar) as
$BODY$
BEGIN
select a.date_value, a.date_id, a.date_desc from dates_tbl a;
END;
$BODY$
LANGUAGE plpgsql;
I am not sure why I am getting the above error. I would like to run select * from tst_dates_func();
and get data back. Or further join the result set if needed. What is the problem here?
Do it as plain SQL
CREATE OR REPLACE FUNCTION tst_dates_func()
RETURNS TABLE( date_value date, date_id int, date_desc varchar) as
$BODY$
select a.date_value, a.date_id, a.date_desc from dates_tbl a;
$BODY$
LANGUAGE sql;
If you really need plpgsql use return query
CREATE OR REPLACE FUNCTION tst_dates_func()
RETURNS TABLE( date_value date, date_id int, date_desc varchar) as
$BODY$
BEGIN
perform SELECT dblink_connect('remote_db');
return query
select a.date_value, a.date_id, a.date_desc from dates_tbl a;
END;
$BODY$
LANGUAGE plpgsql;
In PLPGSQL - use RETURN QUERY
CREATE OR REPLACE FUNCTION tst_dates_func()
RETURNS TABLE( date_value date, date_id int, date_desc varchar) as
$BODY$
BEGIN
RETURN QUERY (select a.date_value, a.date_id, a.date_desc from dates_tbl a);
END;
$BODY$
LANGUAGE plpgsql;
I couldn't do it as plain SQL as I needed to enter some data into a database for further processing and wanted to create a variable. Or at least I did not figure out the correct syntax for that. And the accepted answer had code I did not need, such as connecting to the database, as I ran this from inside pgAdmin with a connection setup already. I also had to drop the function when I made edits to it.
I was using this for inserting a geometry for intersection. A different use case and example could help someone else. This also shows how to then view this data and use it just like a table.
-- Get a geojson shape inside of postgres for further use
DROP FUNCTION fun();
CREATE OR REPLACE FUNCTION fun()
RETURNS TABLE (geometry geometry) AS
$BODY$
DECLARE geojson TEXT;
BEGIN
geojson := '{
"type":"Polygon",
"coordinates":[[[-90.9516399548092,39.8942337977775],[-90.9513913202472,39.8936939306154],[-90.9522805177147,39.8937108246505],[-90.9549542293894,39.8937616571416],[-90.954948768846,39.8945506794343],[-90.9531755591848,39.894492766522],[-90.9531770788457,39.8942868819087],[-90.9516399548092,39.8942337977775]]],
"crs":{"type":"name","properties":{"name":"EPSG:4326"}},
}';
return query (SELECT ST_GeomFromGeoJSON(geojson) AS geometry);
END;
$BODY$
LANGUAGE plpgsql;
-- View test insert
SELECT * FROM fun()
I am using PostgreSQL 8.4 and I want to create a function that returns a query with many rows.
The following function does not work:
create function get_names(varchar) returns setof record AS $$
declare
tname alias for $1;
res setof record;
begin
select * into res from mytable where name = tname;
return res;
end;
$$ LANGUAGE plpgsql;
The type record only allows single row.
How to return an entire query? I want to use functions as query templates.
CREATE OR REPLACE FUNCTION get_names(_tname varchar)
RETURNS TABLE (col_a integer, col_b text) AS
$func$
BEGIN
RETURN QUERY
SELECT t.col_a, t.col_b -- must match RETURNS TABLE
FROM mytable t
WHERE t.name = _tname;
END
$func$ LANGUAGE plpgsql;
Call like this:
SELECT * FROM get_names('name')
Major points:
Use RETURNS TABLE, so you don't have to provide a list of column names with every call.
Use RETURN QUERY, much simpler.
Table-qualify column names to avoid naming conflicts with identically named OUT parameters (including columns declared with RETURNS TABLE).
Use a named variable instead of ALIAS. Simpler, doing the same, and it's the preferred way.
A simple function like this could also be written in LANGUAGE sql:
CREATE OR REPLACE FUNCTION get_names(_tname varchar)
RETURNS TABLE (col_a integer, col_b text) AS
$func$
SELECT t.col_a, t.col_b --, more columns - must match RETURNS above
FROM mytable t
WHERE t.name = $1;
$func$ LANGUAGE sql;
I am able to do the following in SQL where an "array" of user_ids are passed into the where clause of a SQL query.
select * from users where id in (select user_id from profiles);
I would like to do the same thing but pass the "array" into a PostgreSQL (PL/pgSQL) function as shown below. How do I declare the function and work with the "array" within the function?
select * from users_function(select user_id from profiles);
CREATE OR REPLACE FUNCTION users_function(....)
RETURNS void AS
$BODY$
....
Declare an array datatype [] in the function then use the aggregate function array_agg to transform the select statement into an array.
CREATE OR REPLACE FUNCTION users_function(myints integer[])
$$
BEGIN
-- you need to find the bounds with array_lower and array_upper
FOR i in array_lower(myints, 1) .. array_upper(myints, 1) LOOP
Raise Notice '%', myints[i]::integer;
END LOOP;
END;
$$
select * from users_function(array_agg((select user_id from profiles)));
I could not get the nate c's array_agg approach as I described above. This is an option:
select * from test_array('{1,2}');
CREATE OR REPLACE FUNCTION test_array(user_ids integer[])
RETURNS void AS
$$
declare
begin
FOR i in array_lower(user_ids, 1) .. array_upper(user_ids, 1) LOOP
RAISE NOTICE '%', user_ids[i]::integer;
END LOOP;
end
$$
LANGUAGE plpgsql;