问题
I'm having an inordinate amount of trouble using CTEs as arguments to a PostgreSQL function call, and no amount of refactoring into subqueries seems to help; I get either subquery in FROM cannot refer to other relations of same query level
or function expression in FROM cannot refer to other relations of same query level
. The simplified SQL:
create type similarity as (
distance float,
explanation text
);
create or replace function similarity(my_user_id int)
returns table(user_id int, distance float, explanation hstore) as $$
with factors as (
select users.id as user_id, demographics.gender
from users
join demographics on users.id = demographics.user_id),
my_factors as (
select user_id, gender
from factors
where user_id = $1),
similarities as (
select factors.user_id, sim.distance, sim.explanation
from factors, my_factors, similarity_gender(my_factors.gender, factors.gender) as sim)
select user_id, distance, explanation from similarities;
$$ language sql stable strict;
create or replace function similarity_gender(my_gender text, other_gender text) returns similarity as $$
declare
distance float;
sim similarity;
begin
if my_gender is null or other_gender is null then
distance = 0.9;
elsif (my_gender = other_gender) then
distance = 0.0;
else
distance = 1.0;
end if;
sim.distance = distance;
sim.explanation = hstore('gender', cast(sim.distance as text));
return sim;
end;
$$ language plpgsql immutable;
回答1:
For debugging, I created the test scenario:
You should have included that in your setup in the question.
-- drop schema x CASCADE;
create schema x
create table x.users(id int);
create table x.demographics (user_id int, gender text);
INSERT INTO x.users VALUES (1),(2),(3),(4),(5);
INSERT INTO x.demographics VALUES (1, 'm'),(2, 'f'),(3, 'm'),(4, 'f'),(5, 'm');
This works now, after some fixes:
create type x.similarity as (
distance float,
explanation text
);
create or replace function x.similarity_gender(my_gender text, other_gender text)
returns x.similarity as $$
declare
distance float;
sim x.similarity;
begin
if my_gender is null or other_gender is null then
distance = 0.9;
elsif (my_gender = other_gender) then
distance = 0.0;
else
distance = 1.0;
end if;
sim.distance = distance;
sim.explanation = hstore('gender', cast(sim.distance as text));
return sim;
end;
$$ language plpgsql immutable;
create or replace function x.similarity(my_user_id int)
returns table(user_id int, distance float, explanation text) as $$
with factors as (
select u.id as user_id, d.gender
from x.users u
join x.demographics d on u.id = d.user_id),
my_factors as (
select f.user_id, f.gender
from factors f
where f.user_id = $1),
similarities as (
select f.user_id, x.similarity_gender(m.gender, f.gender) AS sim
from factors f, my_factors m)
select s.user_id, (s.sim).distance, (s.sim).explanation
from similarities s;
$$ language sql stable strict;
Call:
test=# SELECT * FROM x.similarity(2);
user_id | distance | explanation
---------+----------+---------------
1 | 1 | "gender"=>"1"
2 | 0 | "gender"=>"0"
3 | 1 | "gender"=>"1"
4 | 0 | "gender"=>"0"
5 | 1 | "gender"=>"1"
Major points
- Create the function first, you have execution sequence reversed in your setup
- In function similarity you must qualify columns names to avoid name conflicts with OUT parameters of the same name (
user_id
,distance
,explanation
). - Your CTE similarities was mangled. I pulled the function call similarity_gender(..) up into the SELECT list. In order not to call twice, I split it up in the next step.
- Use parenthesis to access the fields of composite types. Consult the fine manual here.
- Return type of function similarity() had a bug:
explanation hstore
. Must beexplanation text
.
来源:https://stackoverflow.com/questions/7759498/postgresql-error-subquery-in-from-cannot-refer-to-other-relations-of-same-query