Обсуждение: returning composite types.
Hi guys. I'm working with functions in my database, using plpgsql, but I reached a point where I realize I'm missing a concept: how do I return composite types from a function? I'll give you an example: CREATE TYPE mytype AS( val1 INTEGER, val2 INTEGER, val3 INTEGER, val4 INTEGER ); If I want my function to return a "mytype" type, should I declare it as: CREATE FUNCTION myFunction() RETURNS mytype AS ... or maybe CREATE FUNCTION myFunction() RETURNS SETOF mytype AS ... and in any case, inside the function, how should I declare the variable holding the return value?: DECLARE result mytype; BEGIN ... RETURN result; END; or maybe DECLARE result mytype%ROWTYPE; BEGIN ... RETURN result; END; I've read the documentation and the examples in it, but I still don't understand what the right way is. If you could give an example of a function filling "mytipe" and returning it, it would really help me. Thanks in advance.
Here is how I have been doing mine:<br /><br /><blockquote><tt>CREATE FUNCTION "myFunction" () RETURNS SETOF mytype<br />AS<br /> '<br /> DECLARE<br /> r mytype%ROWTYPE;<br /> BEGIN<br /> FOR r IN [SELECT STATEMENT]<br /> LOOP<br/> RETURN NEXT r;<br /> END LOOP;<br /> RETURN;<br /> END;<br /> '<br /> LANGUAGE 'plpgsql';<br /></tt></blockquote>Hope this Helps..<br /><br /> Jordan S. Jones<br /><br /><br /> Franco Bruno Borghesi wrote:<br /><blockquotecite="mid200303282020.25997.franco@akyasociados.com.ar" type="cite"><pre wrap="">Hi guys. I'm working with functions in my database, using plpgsql, but I reached a point where I realize I'm missing a concept: how do I return composite types from a function? I'll give you an example: CREATE TYPE mytype AS( val1 INTEGER, val2 INTEGER, val3 INTEGER, val4 INTEGER ); If I want my function to return a "mytype" type, should I declare it as: CREATE FUNCTION myFunction() RETURNS mytype AS ... or maybe CREATE FUNCTION myFunction() RETURNS SETOF mytype AS ... and in any case, inside the function, how should I declare the variable holding the return value?: DECLARE result mytype; BEGIN ... RETURN result; END; or maybe DECLARE result mytype%ROWTYPE; BEGIN ... RETURN result; END; I've read the documentation and the examples in it, but I still don't understand what the right way is. If you could give an example of a function filling "mytipe" and returning it, it would really help me. Thanks in advance. </pre></blockquote>
ok, soy you're telling me that the only way to return a composite type is using a set of them, even if I know my function will allways return 1 record. And tell me: can I assign values to this record without using the "for" as you did? maybe a SELECT INTO, or something. I'll tell you what I'm trying to do, maybe that will help: I have 4 functions, that do specific tasks, and they are called in a chained mode. I want the first function in the chain to call the other functions, and return all the results in a composite type, like this: CREATE TYPE mytype AS( val1 INTEGER, val2 INTEGER, val3 INTEGER, val4 INTEGER ); CREATE FUNCTION f1() RETURNS SETOF mytype AS ' DECLARE result mytype%ROWTYPE; BEGIN result.val1=/*something*/; SELECT * INTO result FROM f2(result); RETURN NEXT result; RETURN; END; ' LANGUAGE 'plpgsql'; CREATE FUNCTION f2(mytype) RETURNS SETOF mytype AS ' DECLARE result ALIAS FOR $1; BEGIN result.val2=2; IF (result.val1>50) THEN SELECT * INTO result FROM f3(result); ELSE SELECT * INTOresult FROM f4(result); END IF; RETURN NEXT result; RETURN; END; ' LANGUAGE 'plpgsql'; CREATE FUNCTION f3(mytype) RETURNS SETOF mytype AS ' DECLARE result ALIAS FOR $1; BEGIN /*do something with result*/ RETURN NEXT result; RETURN; END; ' LANGUAGE 'plpgsql'; CREATE FUNCTION f4(mytype) RETURNS SETOF mytype AS ' DECLARE result ALIAS FOR $1; BEGIN /*do something with result*/ RETURN NEXT result; RETURN; END; ' LANGUAGE 'plpgsql'; In a programming language I would pass mytype by reference, and I was trying to something like that here in plpgsql. On Friday 28 March 2003 21:32, Jordan S. Jones wrote: > Here is how I have been doing mine: > > CREATE FUNCTION "myFunction" () RETURNS SETOF mytype > AS > ' > DECLARE > r mytype%ROWTYPE; > BEGIN > FOR r IN [SELECT STATEMENT] > LOOP > RETURN NEXT r; > END LOOP; > RETURN; > END; > ' > LANGUAGE 'plpgsql'; > > Hope this Helps.. > > Jordan S. Jones > > Franco Bruno Borghesi wrote: > >Hi guys. > > > >I'm working with functions in my database, using plpgsql, but I reached a > >point where I realize I'm missing a concept: how do I return composite > > types from a function? I'll give you an example: > > > >CREATE TYPE mytype AS( > > val1 INTEGER, > > val2 INTEGER, > > val3 INTEGER, > > val4 INTEGER > >); > > > >If I want my function to return a "mytype" type, should I declare it as: > >CREATE FUNCTION myFunction() RETURNS mytype AS ... > >or maybe > >CREATE FUNCTION myFunction() RETURNS SETOF mytype AS ... > > > >and in any case, inside the function, how should I declare the variable > >holding the return value?: > > > >DECLARE > > result mytype; > >BEGIN > >... > > RETURN result; > >END; > > > >or maybe > > > >DECLARE > > result mytype%ROWTYPE; > >BEGIN > >... > > RETURN result; > >END; > > > >I've read the documentation and the examples in it, but I still don't > >understand what the right way is. If you could give an example of a > > function filling "mytipe" and returning it, it would really help me. > > > >Thanks in advance.
Franco Bruno Borghesi wrote: > ok, soy you're telling me that the only way to return a composite type is > using a set of them, even if I know my function will allways return 1 record. Try this: create type foo as (f1 int, f2 text); create or replace function retfoo(int, text) returns foo as ' declare result foo%ROWTYPE; begin select into result $1,$2; return result; end; ' language 'plpgsql'; regression=# select * from retfoo(2,'b'); f1 | f2 ----+---- 2 | b (1 row) Joe
yes, i was trying to do something like that, but it breaks always in the same place, first I thought that it was because of the way I was assigning values to the fields of my row, but now I'm beginning to think that the reason is the way I pass the row to f2. Here is the error: franco=# SELECT f1(); WARNING: Error occurred while executing PL/pgSQL function f1 WARNING: line 5 at select into variables ERROR: Attribute "result" not found CREATE TYPE mytype AS (val1 INTEGER, val2 INTEGER, val3 INTEGER); CREATE OR REPLACE FUNCTION f1() RETURNS mytype AS ' DECLARE result mytype%ROWTYPE; BEGIN result.val1:=1; SELECT val2, val3 INTO result.val2, result.val3 FROM f2(result); RETURN result; END; ' LANGUAGE 'plpgsql'; CREATE OR REPLACE FUNCTION f2(mytype) RETURNS mytype AS ' DECLARE arg ALIAS FOR $1; result mytype%ROWTYPE; BEGIN arg.val2:=2; arg.val3:=3; SELECT arg.val1, arg.val2, arg.val3 INTO result.val1, result.val2, result.val3; RETURN result; END; ' LANGUAGE 'plpgsql'; what do you guys think? On Saturday 29 March 2003 13:49, Joe Conway wrote: > Franco Bruno Borghesi wrote: > > ok, soy you're telling me that the only way to return a composite type is > > using a set of them, even if I know my function will allways return 1 > > record. > > Try this: > > create type foo as (f1 int, f2 text); > create or replace function retfoo(int, text) returns foo as ' > declare > result foo%ROWTYPE; > begin > select into result $1, $2; > return result; > end; > ' language 'plpgsql'; > > regression=# select * from retfoo(2,'b'); > f1 | f2 > ----+---- > 2 | b > (1 row) > > Joe
Franco Bruno Borghesi wrote: > yes, i was trying to do something like that, but it breaks always in the same > place, first I thought that it was because of the way I was assigning values > to the fields of my row, but now I'm beginning to think that the reason is > the way I pass the row to f2. > > Here is the error: > franco=# SELECT f1(); > WARNING: Error occurred while executing PL/pgSQL function f1 > WARNING: line 5 at select into variables > ERROR: Attribute "result" not found > > CREATE TYPE mytype AS (val1 INTEGER, val2 INTEGER, val3 INTEGER); > > CREATE OR REPLACE FUNCTION f1() RETURNS mytype AS ' > DECLARE > result mytype%ROWTYPE; > BEGIN > result.val1:=1; > SELECT val2, val3 INTO result.val2, result.val3 FROM f2(result); It looks like plpgsql doesn't support composite type variables as arguments to functions that are called from within a function. The error is saying it cannot find an attribute named result -- that's because there is no *attribute* called result, there is a rowtype variable. I'm not sure right off what is involved in fixing this, but you can always pass the individual attributes to f2: CREATE TYPE mytype AS (val1 INTEGER, val2 INTEGER, val3 INTEGER); CREATE OR REPLACE FUNCTION f2(int,int,int) RETURNS mytype AS ' DECLARE arg1 ALIAS FOR $1; arg2 ALIAS FOR $2; arg3 ALIAS FOR $3; newval2 int; newval3 int; result mytype%ROWTYPE; BEGIN newval2 := coalesce(arg2,2) * arg1; newval3 := coalesce(arg3,3) * arg1; SELECT INTO result.val1, result.val2,result.val3 arg1, newval2, newval3; RETURN result; END; ' LANGUAGE 'plpgsql'; CREATE OR REPLACE FUNCTION f1(int) RETURNS mytype AS ' DECLARE result mytype%ROWTYPE; BEGIN result.val1:=$1; SELECT INTO result.val2, result.val3 val2, val3 FROM f2(result.val1, result.val2, result.val3); RETURN result; END; ' LANGUAGE 'plpgsql'; regression=# select * from f1(2); val1 | val2 | val3 ------+------+------ 2 | 4 | 6 (1 row) HTH, Joe
so what you're saying is that it's not a syntactical error, it's just an unsupported feature. Ok then, I will just call my functions sending the values from my composite type individually. thanks guys! On Saturday 29 March 2003 15:25, Joe Conway wrote: > Franco Bruno Borghesi wrote: > > yes, i was trying to do something like that, but it breaks always in the > > same place, first I thought that it was because of the way I was > > assigning values to the fields of my row, but now I'm beginning to think > > that the reason is the way I pass the row to f2. > > > > Here is the error: > > franco=# SELECT f1(); > > WARNING: Error occurred while executing PL/pgSQL function f1 > > WARNING: line 5 at select into variables > > ERROR: Attribute "result" not found > > > > CREATE TYPE mytype AS (val1 INTEGER, val2 INTEGER, val3 INTEGER); > > > > CREATE OR REPLACE FUNCTION f1() RETURNS mytype AS ' > > DECLARE > > result mytype%ROWTYPE; > > BEGIN > > result.val1:=1; > > SELECT val2, val3 INTO result.val2, result.val3 FROM f2(result); > > It looks like plpgsql doesn't support composite type variables as > arguments to functions that are called from within a function. The error > is saying it cannot find an attribute named result -- that's because > there is no *attribute* called result, there is a rowtype variable. > > I'm not sure right off what is involved in fixing this, but you can > always pass the individual attributes to f2: > > CREATE TYPE mytype AS (val1 INTEGER, val2 INTEGER, val3 INTEGER); > > CREATE OR REPLACE FUNCTION f2(int,int,int) RETURNS mytype AS ' > DECLARE > arg1 ALIAS FOR $1; > arg2 ALIAS FOR $2; > arg3 ALIAS FOR $3; > newval2 int; > newval3 int; > result mytype%ROWTYPE; > BEGIN > newval2 := coalesce(arg2,2) * arg1; > newval3 := coalesce(arg3,3) * arg1; > SELECT INTO result.val1, result.val2, result.val3 > arg1, newval2, newval3; > RETURN result; > END; > ' LANGUAGE 'plpgsql'; > > CREATE OR REPLACE FUNCTION f1(int) RETURNS mytype AS ' > DECLARE > result mytype%ROWTYPE; > BEGIN > result.val1:=$1; > SELECT INTO result.val2, result.val3 val2, val3 > FROM f2(result.val1, result.val2, result.val3); > RETURN result; > END; > ' LANGUAGE 'plpgsql'; > > regression=# select * from f1(2); > val1 | val2 | val3 > ------+------+------ > 2 | 4 | 6 > (1 row) > > HTH, > > Joe