I want a plpgsql function that returns the content of any table, given the name. The function below, although not working because of many reasons will gove you the general idea. Safety and coding practice aside, what's the easiest way to accomplish this?
In the end I want to get these results trough a Java CallableStatement.
CREATE OR REPLACE FUNCTION get_table(tablename VARCHAR)
RETURNS SETOF RECORD AS $PROC$
BEGIN
RETURN QUERY SELECT * FROM tablename;
END;
$PROC$ LANGUAGE 'plpgsql';
You can get your function working like this:
CREATE OR REPLACE FUNCTION get_table(tablename VARCHAR)
RETURNS SETOF RECORD AS $PROC$
BEGIN
RETURN QUERY EXECUTE 'SELECT * FROM ' || quote_ident(tablename);
END;
$PROC$ LANGUAGE 'plpgsql';
In order to call it, you must specify names and data types for all returned columns. If you want to list table "t" which has two columns, you could use your function like this:
SELECT * FROM get_table('t') x(id int, val text);
Which of course, is longer and a lot more trouble than either:
SELECT * FROM t;
or the equivalent:
TABLE t;
I really can't imagine a use-case where such a function makes anything better.
Related
As I am newbie to plpgSQL,
I stuck while migrating a Oracle query into PostgreSQL.
Oracle query:
create or replace FUNCTION employee_all_case(
p_ugr_id IN integer,
p_case_type_id IN integer
)
RETURN number_tab_t PIPELINED
-- LANGUAGE 'plpgsql'
-- COST 100
-- VOLATILE
-- AS $$
-- DECLARE
is
l_user_id NUMBER;
l_account_id NUMBER;
BEGIN
l_user_id := p_ugr_id;
l_account_id := p_case_type_id;
FOR cases IN
(SELECT ccase.case_id, ccase.employee_id
FROM ct_case ccase
INNER JOIN ct_case_type ctype
ON (ccase.case_type_id=ctype.case_type_id)
WHERE ccase.employee_id = l_user_id)
LOOP
IF cases.employee_id IS NOT NULL THEN
PIPE ROW (cases.case_id);
END IF;
END LOOP;
RETURN;
END;
--$$
When I execute this function then I get the following result
select * from table(select employee_all_case(14533,1190) from dual)
My question here is: I really do not understand the pipelined function and how can I obtain the same result in PostgreSQL as Oracle query ?
Please help.
Thank you guys, your solution was very helpful.
I found the desire result:
-- select * from employee_all_case(14533,1190);
-- drop function employee_all_case
create or replace FUNCTION employee_all_case(p_ugr_id IN integer ,p_case_type_id IN integer)
returns table (case_id double precision)
-- PIPELINED
LANGUAGE 'plpgsql'
COST 100
VOLATILE
AS $$
DECLARE
-- is
l_user_id integer;
l_account_id integer;
BEGIN
l_user_id := cp_lookup$get_user_id_from_ugr_id(p_ugr_id);
l_account_id := cp_lookup$acctid_from_ugr(p_ugr_id);
RETURN QUERY SELECT ccase.case_id
FROM ct_case ccase
INNER JOIN ct_case_type ctype ON ccase.case_type_id = ctype.case_type_id
WHERE ccase.employee_id = p_ugr_id
and ccase.employee_id IS NOT NULL;
--return NEXT;
END;
$$
You would rewrite that to a set returning function:
Change the return type to
RETURNS SETOF integer
and do away with the PIPELINED.
Change the PIPE ROW statement to
RETURN NEXT cases.case_id;
Of course, you will have to do the obvious syntactic changes, like using integer instead of NUMBER and putting the IN before the parameter name.
But actually, it is quite unnecessary to write a function for that. Doing it in a single SELECT statement would be both simpler and faster.
Pipelined functions are best translated to a simple SQL function returning a table.
Something like this:
create or replace function employee_all_case(p_ugr_id integer, p_case_type_IN integer)
returns table (case_id integer)
as
$$
SELECT ccase.case_id
FROM ct_case ccase
INNER JOIN ct_case_type ctype ON ccase.case_type_id = ctype.case_type_id
WHERE ccase.employee_id = p_ugr_id
and cases.employee_id IS NOT NULL;
$$
language sql;
Note that your sample code did not use the second parameter p_case_type_id.
Usage is also more straightforward:
select *
from employee_all_case(14533,1190);
Before diving into the solution, I will provide some information which will help you to understand better.
So basically PIPELINED came into picture for improving memory allocation at run time.
As you all know collections will occupy space when ever they got created. So the more you use, the more memory will get allocated.
Pipelining negates the need to build huge collections by piping rows out of the function.
saving memory and allowing subsequent processing to start before all the rows are generated.
Pipelined table functions include the PIPELINED clause and use the PIPE ROW call to push rows out of the function as soon as they are created, rather than building up a table collection.
By using Pipelined how memory usage will be optimized?
Well, it's very simple. instead of storing data into an array, just process the data by using pipe row(desired type). This actually returns the row and process the next row.
coming to solution in plpgsql
simple but not preferred while storing large data.
Remove PIPELINED from return declaration and return an array of desired type. something like RETURNS typrec2[].
Where ever you are using pipe row(), add that entry to array and finally return that array.
create a temp table like
CREATE TEMPORARY TABLE temp_table (required fields) ON COMMIT DROP;
and insert data into it. Replace pipe row with insert statement and finally return statement like
return query select * from temp_table
**The best link for understanding PIPELINED in oracle [https://oracle-base.com/articles/misc/pipelined-table-functions]
pretty ordinary for postgres reference [http://manojadinesh.blogspot.com/2011/11/pipelined-in-oracle-as-well-in.html]
Hope this helps some one conceptually.
I'm trying to store a simple SELECT query with the new CREATE PROCEDURE method in PostgreSQL 11. My idea is to store the queries in the DB, because I can have a much simple code in my API server and maybe I don't need to develop a query builder if I can use if/else in an sql function with enforced type safety. I have this minimal example:
First I tried this plpgsql function:
CREATE OR REPLACE PROCEDURE test_proc() AS $$
BEGIN
SELECT * FROM my_db
LIMIT 1;
END;
$$ LANGUAGE plpgsql;
CALL test_proc();
However throws this error:
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 test_proc() line 3 at SQL statement SQL state: 42601
If I trying to use RETURN QUERY:
CREATE OR REPLACE PROCEDURE test_proc() AS $$
BEGIN
RETURN QUERY;
SELECT * FROM my_db
LIMIT 1;
END;
$$ LANGUAGE plpgsql;
I'm getting this error:
ERROR: cannot use RETURN QUERY in a non-SETOF function
LINE 17: RETURN QUERY; ^
SQL state: 42804
Character: 310
I'm also getting error when I try to use RETURNS void AS $$ or RETURNS table(...) AS $$. Seems like RETURNS not supported in CREATE PROCEDURE? So, is it possible to return a table with the new stored procedure method? Or if it's not, maybe JSON?
Procedures in PostgreSQL (Oracle, DB2) are not same like procedures in MS-SQL. It has different target, and you cannot use it. Usually, the best what you can do, forgot all what you know from MSSQL. The procedural part is really different.
Only functions can returns some data - so you need to use functions. Functions can returns scalar value, composite value or array value, or table. You want function that returns table.
CREATE OR REPLACE FUNCTION fx()
RETURNS SETOF mytab AS $$
BEGIN
RETURN QUERY SELECT * FROM mytab;
END
$$ LANGUAGE plpgsql;
SELECT * FROM fx();
For record:
You can use SQL function, that can have better (or worse) performance (depends on context). These functions are sometimes named as parametrized views.
CREATE OR REPLACE FUNCTION fx()
RETURNS SETOF mytab AS $$
SELECT * FROM mytab;
$$ LANGUAGE sql;
Attention: this technique is antipattern!!! Don't do it. It is really not good idea. The functions should not to wrap queries. If you want to hide some complexity of queries, then use a views. Don't use a functions. Functions are effective barier for query optimizer, and when you use this antipattern, then optimizer cannot to well optimize any non trivial queries that use in this form evaluated subqueries.
Use it - if you want very very slow applications - or if your data model or queries are primitive. In other cases, don't do it.
Don't afraid of SQL - it is great language designed for manual usage. It is good to place all data access to one module (model), to don't access database everywhere in your code, but it is bad too hide SQL in your code.
First of all Procedure was introduced in PostgreSQL 11, If you are using below 11th version, you cannot use Procedures. Instead to Procedure you can use functions.
Syntax to create function
CREATE or replace function function_name(_parameter varchar)
returns table(col1 varchar, col2 varchar, col3 varchar)
language 'plpgsql'
as $BODY$
BEGIN
return query select a.col1, a.col2, b.col3 from table a
join table2 as b on a.col1 = b.col1;
END;
$BODY$;
you can call a function same a like table
select * From function_name('sample data');
syntax to create Procedure.
CREATE OR REPLACE PROCEDURE procedure_name(_parameter varcar,INOUT result refcursor)
LANGUAGE 'plpgsql'
AS $BODY$
BEGIN
open result for SELECT , * from sampletable where a = _parameter;
END;
$BODY$;
you can execute a Procedure using call keyword, within a transaction
BEGIN;
CALL public.procedure_name( 'sample data', 'test');
fetch all in "test";
COMMIT;
The postgreSql 11. we have to create a stored procedure
there is the solution :
Create procedure to execute query in PostgreSQL
I have a sql UPDATE statement in a plpgsql function. I now want to call the pg_notify function for each updated row and am uncertain if my solution is the best possibility.
I am not aware of any position in the UPDATE statement itself where I could apply the function. I don't think it is possible in the SET part and if I would apply the function in the WHERE part, it would be applied to each row as it is checked and not only the updated rows, correct?
I therefore thought I could use the RETURNING part for my purposes and designed the function like this:
CREATE OR REPLACE FUNCTION function_name() RETURNS VOID AS $BODY$
BEGIN
UPDATE table1
SET a = TRUE
FROM table2
WHERE table1.b = table2.c
AND <more conditions>
RETURNING pg_notify('notification_name', table1.pk);
END;
$BODY$ LANGUAGE 'plpgsql' VOLATILE;
Unfortunately this gave me an error saying that I am not using or storing the return value of the query anywhere. I therefore tried putting PERFORM in front of the query but this seemed to be syntactically incorrect.
After trying different combinations with PERFORM my ultimate solution is this:
CREATE OR REPLACE FUNCTION function_name() RETURNS VOID AS $BODY$
DECLARE
dev_null INTEGER;
BEGIN
WITH updated AS (
UPDATE table1
SET a = TRUE
FROM table2
WHERE table1.b = table2.c
AND <more conditions>
RETURNING pg_notify('notification_name', table1.pk)
)
SELECT 1 INTO dev_null;
END;
$BODY$ LANGUAGE 'plpgsql' VOLATILE;
This works as it is supposed to, but I feel like there should be a better solution which does not temporarily store a useless result and does not use a useless variable.
Thank you for your help.
** EDIT 1 **
As can be seen in #pnorton 's answer, a trigger would do the trick in most cases. For me, however, it is not applicable as the receiver of the notifications also sometimes updates the table and I do not want to generate notifications in such a case
"I have a sql UPDATE statement in a plpgsql function. I now want to
call the pg_notify function for each updated row "
Ok I might be tempted to use a trigger Eg
CREATE TABLE foobar (id serial primary key, name varchar);
CREATE OR REPLACE FUNCTION notify_trigger() RETURNS trigger AS $$
DECLARE
BEGIN
PERFORM pg_notify('watch_tb_update', TG_TABLE_NAME || ',id,' || NEW.id );
RETURN new;
END;
$$ LANGUAGE plpgsql;
CREATE TRIGGER foobar_trigger AFTER INSERT ON foobar
FOR EACH ROW EXECUTE PROCEDURE notify_trigger();
LISTEN watch_tb_update;
INSERT into foobar(id, name) values(1,'test_name');
I've tested this and it works fine
I am trying to implement a function that returns a table with the same structure as an input table in the parameter, using PL/pgSQL (PostgreSQL 9.3). Basically, I want to update a table, and return a copy of the updated table with plpgsql. I searched around SO and found several related questions (e.g. Return dynamic table with unknown columns from PL/pgSQL function and Table name as a PostgreSQL function parameter), which lead to the following minimal test example:
CREATE OR REPLACE FUNCTION change_val(_lookup_tbl regclass)
RETURNS _lookup_tbl%rowtype AS --problem line
$func$
BEGIN
RETURN QUERY EXECUTE format('UPDATE %s SET val = 2 RETURNING * ; ', _lookup_tbl);
END
$func$ LANGUAGE plpgsql;
But I can't get past giving the correct return type for TABLE or SETOF RECORD in the problem line. According to this answer:
SQL demands to know the return type at call time
But I think the return type (which I intend to borrow from the input table type) is known. Can some one help explain if it is possible to fix the signature of the above PL/pgSQL function?
Note, I need to parametrize the input table and return the update of that table. Alternatives are welcome.
What you have so far looks good. The missing ingredient: polymorphic types.
CREATE OR REPLACE FUNCTION change_val(_tbl_type anyelement)
RETURNS SETOF anyelement -- problem solved
LANGUAGE plpgsql AS
$func$
BEGIN
RETURN QUERY EXECUTE format(
'UPDATE %s SET val = 2 RETURNING *;'
, pg_typeof(_tbl_type))
);
END
$func$;
Call (important):
SELECT * FROM change_val(NULL::some_tbl);
db<>fiddle here
Old sqlfiddle
See (last paragraph):
Refactor a PL/pgSQL function to return the output of various SELECT queries
I need to show the Tree_Nodes table data
CREATE OR REPLACE FUNCTION sample()
RETURNS TABLE() AS
$BODY$
BEGIN
select * from "Tree_Nodes";
END;
$BODY$
LANGUAGE plpgsql VOLATILE
COST 100
ROWS 1000;
ALTER FUNCTION sample()
OWNER TO postgres;
It fails with:
ERROR: query has no destination for result data
Avoid the error and i will get the table column format in all data
To return the result of a SELECT, a pure SQL function is much more suitable:
CREATE OR REPLACE FUNCTION sample()
RETURNS TABLE ( .... ) AS
$BODY$
select * from "Tree_Nodes";
$BODY$
LANGUAGE sql;
Or if you really need PL/pgSQL, you need to use return query (which is clearly documented in the manual)
CREATE OR REPLACE FUNCTION sample()
RETURNS TABLE (....)
AS
$BODY$
BEGIN
return query select * from "Tree_Nodes";
END;
$BODY$
LANGUAGE plpgsql;
But you cannot just specify returns table() you have to also define the structure of the result:
CREATE OR REPLACE FUNCTION sample()
RETURNS TABLE(id integer, some_column text, other_column decimal(10,2), ...)
AS
The exact error you quote is caused by using SELECT without an INTO clause in PL/PgSQL. You must either use SELECT INTO somevariable, use RETURN QUERY, if you want to discard the data, use the PERFORM statement instead of SELECT, as covered by the PL/PgSQL manual.
Once you fix that by using RETURN QUERY SELECT .... you'll find that the function still doesn't work, because RETURNS TABLE() doesn't make sense. You're returning an empty result set. It'll fail, complaining that the statement is returning a result set that doesn't match the function.
It makes no sense to do this anyway, since you can just write it as a trivial SQL function like:
CREATE OR REPLACE FUNCTION sample()
RETURNS SETOF "Tree_Nodes"
AS $$
SELECT * FROM "Tree_Nodes";
$$ LANGUAGE sql;
This function appears to serve no purpose. What are you trying to achieve with it?
(By the way, you should generally avoid SELECT * in production code. List the columns. That way, if you add a column later, things that use the table won't suddenly stop working.)