PostgreSQL SQL - Multiple SRF parameters from query

Author

Multiple SRF parameters from query

Federico Pedemonte

2005-05-31, 11:23 am

Hi All,

i'm having troubles trying to write a sql query using a Set Returning
Function.

I have a function foo (ID varchar) that returns a variable number of
records.
I have also a table (called Anagrafica) that contains a list of IDs to
be passed to the function foo.

As an example, just say that Anagrafica is like this:

Anagrafica

ID | n
----+---
aaa | 1
bbb | 5
ccc | 9
ddd | 10
eee | 11

and foo returns this values

select * from foo ('aaa')

a | b | c
--+---+---
1 | 2 | 3
5 | 9 | 1

select * from foo ('bbb')

a | b | c
--+---+---
4 | 0 | 0
2 | 0 | 0
0 | 0 | 0

what i would like to do is write an SQL query that looks something like
this (written in simplyfied-pseudo-sql)

SELECT FROM anagrafica
WHERE n < 5
SELECT * FROM Foo (anagrafica.ID)

and that gives as result a table that is the union of foo ('aaa') and
foo ('bbb')

a | b | c
--+---+---
1 | 2 | 3
5 | 9 | 1
4 | 0 | 0
2 | 0 | 0
0 | 0 | 0

I'm having success if foo returns only a row, but the problem is that
foo returns more than one.
I think i sould use a join but i couldn't find the right syntax for it.

I don't want to create a spefic PL/pgSQL function becase i need to have
freedom in selecting IDs from Anagrafica (the one i provided is just an
example, the real table is much more complex).

I would really appreciate any suggestion.

Best regards,
Federico.

---------------------------(end of broadcast)---------------------------
TIP 1: subscribe and unsubscribe commands go to majordomo@postgresql
.org

Federico Pedemonte

2005-06-04, 11:23 am

On Wed, 2005-06-01 at 10:29 +0530, Ramakrishnan Muralidharan wrote:
> Hi,
>
> I am not able to understand "Returning only one row", since 'aaa' having 2 rows and 'bbb' having 3 rows and what criteria single row should be returned. Please let me know the expected result and I will try to find out a solution for it.

Sorry, it was not clear from my message.

I meant that I had success creating a table as a result of multiple
invocation of foo (parameter) using the result of an "outer" query as
list of parameter to foo, only if foo () is a "normal" function,
returning a simple value.

It was a misleading sentence anyway, since what i'm asking help for is
the case where foo () is a SRF and returns more than 1 row.

What i'm trying to do is a query where i get a result of this kind

a | b | c
--+---+---
1 | 2 | 3
5 | 9 | 1
4 | 0 | 0
2 | 0 | 0
0 | 0 | 0

given that i select from the table Anagrafica the fields 'aaa' and
'bbb', where the first 2 rows obtained as the result of foo ('aaa') and
the latter 3 as the result of foo ('bbb').

Thanks a lot for help !

PS: Sorry for late answering, i had problems with mail.

Regards,
Federico.

---------------------------(end of broadcast)---------------------------
TIP 4: Don't 'kill -9' the postmaster

Michael Fuhr

2005-06-04, 8:23 pm

On Sat, Jun 04, 2005 at 06:19:35PM +0200, Federico Pedemonte wrote:
>
> What i'm trying to do is a query where i get a result of this kind
>
> a | b | c
> --+---+---
> 1 | 2 | 3
> 5 | 9 | 1
> 4 | 0 | 0
> 2 | 0 | 0
> 0 | 0 | 0
>
> given that i select from the table Anagrafica the fields 'aaa' and
> 'bbb', where the first 2 rows obtained as the result of foo ('aaa') and
> the latter 3 as the result of foo ('bbb').

If you don't mind using a deprecated feature that might be removed
from future versions of PostgreSQL, then see "SQL Functions Returning
Sets" in the documentation:

http://www.postgresql.org/docs/8.0/...l.html#AEN29555

To use the deprecated feature, you could wrap a complex PL/pgSQL
SRF inside a simple SQL SRF. The following example works for me
in 8.0.3:

CREATE TABLE anagrafica (
id text PRIMARY KEY,
n integer NOT NULL
);

INSERT INTO anagrafica (id, n) VALUES ('aaa', 1);
INSERT INTO anagrafica (id, n) VALUES ('bbb', 5);
INSERT INTO anagrafica (id, n) VALUES ('ccc', 9);
INSERT INTO anagrafica (id, n) VALUES ('ddd', 10);
INSERT INTO anagrafica (id, n) VALUES ('eee', 11);

CREATE TYPE footype AS (
a integer,
b integer,
c integer
);

CREATE FUNCTION foo(id text) RETURNS SETOF footype AS $$
DECLARE
rec footype;
BEGIN
IF id = 'aaa' THEN
rec.a := 1; rec.b := 2; rec.c := 3; RETURN NEXT rec;
rec.a := 5; rec.b := 9; rec.c := 1; RETURN NEXT rec;
RETURN;
ELSIF id = 'bbb' THEN
rec.a := 4; rec.b := 0; rec.c := 0; RETURN NEXT rec;
rec.a := 2; rec.b := 0; rec.c := 0; RETURN NEXT rec;
rec.a := 0; rec.b := 0; rec.c := 0; RETURN NEXT rec;
RETURN;
ELSE
rec.a := -1; rec.b := -2; rec.c := -3; RETURN NEXT rec;
RETURN;
END IF;
END;
$$ LANGUAGE plpgsql STABLE STRICT;

CREATE FUNCTION bar(text) RETURNS SETOF footype AS $$
SELECT * FROM foo($1);
$$ LANGUAGE sql STABLE STRICT;

SELECT (bar(id)).* FROM anagrafica WHERE n <= 5;
a | b | c
---+---+---
1 | 2 | 3
5 | 9 | 1
4 | 0 | 0
2 | 0 | 0
0 | 0 | 0
(5 rows)

I don't know if there's a way to do this in a simple query without
relying on the deprecated behavior. For forward compatibility, you
might be better off writing a SRF that makes a query and loops
through the results, like this:

CREATE FUNCTION baz(query text) RETURNS SETOF footype AS $$
DECLARE
rec record;
retval footype;
BEGIN
FOR rec IN EXECUTE query LOOP
IF rec.id = 'aaa' THEN
retval.a := 1; retval.b := 2; retval.c := 3; RETURN NEXT retval;
retval.a := 5; retval.b := 9; retval.c := 1; RETURN NEXT retval;
ELSIF rec.id = 'bbb' THEN
retval.a := 4; retval.b := 0; retval.c := 0; RETURN NEXT retval;
retval.a := 2; retval.b := 0; retval.c := 0; RETURN NEXT retval;
retval.a := 0; retval.b := 0; retval.c := 0; RETURN NEXT retval;
ELSE
retval.a := -1; retval.b := -2; retval.c := -3; RETURN NEXT retval;
END IF;
END LOOP;

RETURN;
END;
$$ LANGUAGE plpgsql STABLE STRICT;

SELECT * FROM baz('SELECT * FROM anagrafica WHERE n <= 5');
a | b | c
---+---+---
1 | 2 | 3
5 | 9 | 1
4 | 0 | 0
2 | 0 | 0
0 | 0 | 0
(5 rows)

Maybe somebody else can suggest improvements or alternatives.

--
Michael Fuhr
http://www.fuhr.org/~mfuhr/

---------------------------(end of broadcast)---------------------------
TIP 7: don't forget to increase your free space map settings

Ramakrishnan Muralidharan

2005-06-05, 8:24 pm

Hi,

I am not able to understand "Returning only one row", since 'aaa' having 2 rows and 'bbb' having 3 rows and what criteria single row should be returned. Please let me know the expected result and I will try to find out a solution for it.

for set returning function the following link maybe helpful
http://techdocs.postgresql.org/guid...unction
s

Regards,
R.Muralidharan

-----Original Message-----
From: pgsql-sql-owner@postgresql.org
[mailto:pgsql-sql-owner@postgresql.org]On Behalf Of Federico Pedemonte
Sent: Tuesday, May 31, 2005 8:23 PM
To: pgsql-sql@postgresql.org
Subject: [SQL] Multiple SRF parameters from query

Hi All,

i'm having troubles trying to write a sql query using a Set Returning
Function.

I have a function foo (ID varchar) that returns a variable number of
records.
I have also a table (called Anagrafica) that contains a list of IDs to
be passed to the function foo.

As an example, just say that Anagrafica is like this:

Anagrafica

ID | n
----+---
aaa | 1
bbb | 5
ccc | 9
ddd | 10
eee | 11

and foo returns this values

select * from foo ('aaa')

a | b | c
--+---+---
1 | 2 | 3
5 | 9 | 1

select * from foo ('bbb')

a | b | c
--+---+---
4 | 0 | 0
2 | 0 | 0
0 | 0 | 0

what i would like to do is write an SQL query that looks something like
this (written in simplyfied-pseudo-sql)

SELECT FROM anagrafica
WHERE n < 5
SELECT * FROM Foo (anagrafica.ID)

and that gives as result a table that is the union of foo ('aaa') and
foo ('bbb')

a | b | c
--+---+---
1 | 2 | 3
5 | 9 | 1
4 | 0 | 0
2 | 0 | 0
0 | 0 | 0

I'm having success if foo returns only a row, but the problem is that
foo returns more than one.
I think i sould use a join but i couldn't find the right syntax for it.

I don't want to create a spefic PL/pgSQL function becase i need to have
freedom in selecting IDs from Anagrafica (the one i provided is just an
example, the real table is much more complex).

I would really appreciate any suggestion.

Best regards,
Federico.

---------------------------(end of broadcast)---------------------------
TIP 1: subscribe and unsubscribe commands go to majordomo@postgresql
.org

---------------------------(end of broadcast)---------------------------
TIP 9: the planner will ignore your desire to choose an index scan if your
joining column's datatypes do not match

Sponsored Links