NOTE: plsh is a PostgreSQL language that executes shell commands.
I'm trying to call a plsh function from within a plpgsql function.
First there's the bigger plpgsql function:
CREATE OR REPLACE FUNCTION my_schema.big_function(my_arg character varying)
RETURNS text AS
$BODY$
BEGIN
DROP TABLE IF EXISTS backend.table_B;
CREATE TABLE backend.table_B AS
--Create a table with a SELECT with some joins,
--right now the resulting table is empty
RAISE NOTICE 'table_B created';
PERFORM my_schema.insert_from_shell(my_arg);
RETURN 'Function Ended';
END;
$BODY$
LANGUAGE plpgsql VOLATILE
COST 100;
Then there's the plsh function:
CREATE OR REPLACE FUNCTION my_schema.insert_from_shell(my_arg character varying)
RETURNS text AS
$BODY$
#!/bin/sh
PGPASSWORD=mypassword psql -d mydatabase -h myhost -p myport -U myuser -c "INSERT INTO myschema.table_A(mycolumn) VALUES('$1')"
$BODY$
LANGUAGE plsh VOLATILE
COST 100;
When I try to execute the following:
SELECT my_schema.big_function('test');
it never ends. On the other hand, if I comment the PERFORM line from the first function, and call both functions separately, they each end in less than a second:
SELECT my_schema.big_function('test');
SELECT my_schema.insert_from_shell('test');
There might be a problem with executing plsh functions from within plpgsql functions, but I'm not sure.
I could work around it calling both functions separately using a script outside the database, but I'd rather solve it from within the database, and call a single function.
Any pointer or help will be greatly appreciated.
Assuming that a trigger in the transaction of big_function puts a conflicting lock on table_a, as suggested in the comment, you could consider the following solution:
Make the trigger a CONSTRAINT TRIGGER (it has to be an AFTER trigger then) and declare it as DEFERRABLE INITIALLY DEFERRED. Then it will not run right when the triggering statement does, but will be deferred to the COMMIT at the end of the transaction.
By that time, insert_from_shell has finished and committed, so there will be no deadlock.
Related
Every time I dump my structure.sql on a rails app, I get PROCEDURE over FUNCTION. FUNCTION is our default and I have to commit the file in parts which is annoying and sometimes I miss lines which is even worse, as it is a rather big structure.sql file.
git diff example:
-CREATE TRIGGER cache_comments_count AFTER INSERT OR DELETE OR UPDATE ON public.comments FOR EACH ROW EXECUTE PROCEDURE public.update_comments_counter();
+CREATE TRIGGER cache_comments_count AFTER INSERT OR DELETE OR UPDATE ON public.comments FOR EACH ROW EXECUTE FUNCTION public.update_comments_counter();
I'm sure there is a postgresql setting for this somewhere, but I can't find it.
Whether you use Function or Procedure you get exactly the same. The documentation shows
CREATE [ CONSTRAINT ] TRIGGER name...
EXECUTE { FUNCTION | PROCEDURE } function_name ( arguments )
This means you can use either term FUNCTION or PROCEDURE but either way function_name is always called. See demo. For demo I have separate triggers for insert and update. Insert using execute procedure and update using execute function. This cannot be changed in Postgres it would have to be Rails setting. NOTE: Prior to v11 Postgres only allowed execute procedure even though you had to create a trigger function that was called.
The function pg_get_triggerdef() changed between Postgres 11 and 12 when Postgres introduced real procedures. Since Postgres 12 it always returns a syntax that uses EXECUTE FUNCTION as in reality it is a function that is called when the trigger fires, not a procedure.
So this code:
create table t1 (id int);
create function trg_func()
returns trigger
as
$$
begin
return new;
end;
$$
language plpgsql;
create trigger test_trigger
before insert or update
on t1
for each row
execute procedure trg_func();
select pg_get_triggerdef(oid)
from pg_trigger
where tgname = 'test_trigger';
returns the following in Postgres 11 and earlier:
CREATE TRIGGER test_trigger BEFORE INSERT OR UPDATE ON public.t1 FOR EACH ROW EXECUTE PROCEDURE trg_func()
and the following in Postgres 12 and later:
CREATE TRIGGER test_trigger BEFORE INSERT OR UPDATE ON public.t1 FOR EACH ROW EXECUTE FUNCTION trg_func()
I guess Rails uses pg_get_triggerdef() to obtain the trigger source. So there is nothing you can do. If you want a consistent result, you should use the same Postgres version everywhere.
The column action_statement in the view information_schema.triggers also reflects the change in naming.
Postgres 11 example
Postgres 12 example
I'm new to Postgres, but with experience from Oracle. Trying to create a stored procedure which is going to:
Insert a row
Handle exceptions and in case of an exception insert a row into a log table by calling dedicated procedure
Emit an audit log record into a log table in case the whole procedure ran successfully
By pseudo code:
CREATE OR REPLACE PROCEDURE test.p_insert(IN p_test_param character varying)
LANGUAGE 'plpgsql'
SECURITY DEFINER
AS $BODY$
DECLARE
-- some declarations
BEGIN
BEGIN
INSERT INTO test.a(a) VALUES (p_test_param);
EXCEPTION
WHEN OTHERS THEN
-- GET STACKED DIAGNOSTICS
CALL test.p_insert_log(...); -- Inserts a row into a log table, another COMMIT may be required?
RAISE;
END;
COMMIT; -- CAN'T DO
BEGIN
IF (SELECT test.f_debug()) THEN
CALL test.p_insert_log(...); -- Audit the execution
END IF;
END;
COMMIT; -- CAN'T DO EITHER
END;
$$BODY$$;
However when I try to test the procedure out from an anonymous block in PgAdmin such as:
BEGIN;
DO
LANGUAGE plpgsql
$$
BEGIN
CALL test.p_insert(
p_test_param => 'test'
);
END;
$$
I'm getting an error ERROR: invalid transaction termination. How can I get rid of it? My objective is to let the procedure carry out the transaction control, I don't want the caller to COMMIT or ROLLBACK anything. If I remove both COMMIT commands from the code of the procedure, it executes well, however the invoker must explicitly COMMIT or REVOKE the transaction afterwards, which is not desired. In Oracle the pseudo code with COMMIT statements would work, in Postgres it doesn't seem to work as I would like to. Could you please help me out? Thanks
Your code will work as intended. Perhaps you made some mistake in calling the code:
you cannot call the procedure from a function
you cannot call the procedure in an explicitly started transaction:
BEGIN;
CALL p_insert('something); -- will fail
COMMIT;
I'm trying to create a PostgreSQL event trigger, that fires whenever a user creates anything (table, view, function, sequence...) and sets the owner of this newly created thing to a certain role.
So far I have the even trigger itself, that fires on any CREATE command:
CREATE EVENT TRIGGER setOwnerToMyRole ON ddl_command_end
WHEN tg_tag LIKE 'CREATE%'
EXECUTE PROCEDURE setOwnerToMyRole();
But I am having problems with the function itself:
CREATE FUNCTION setOwnerToMyRole() RETURNS event_trigger LANGUAGE plpgsql
AS $$ BEGIN
ALTER <type> <name> OWNER TO myRole
END; $$;
How do I get the type (as in table, view, etc.) and how do i get the name of the newly created thing?
edit:
Looking at this question and this question and of course CREATE EVENT TRIGGER and Trigger Procedures, this is currently not really possible :(
This works pretty well for me, although it's a little broader net than needed. It is based on code at https://blog.hagander.net/setting-owner-at-create-table-237/
CREATE OR REPLACE FUNCTION trg_create_set_owner()
RETURNS event_trigger
LANGUAGE plpgsql
AS $$
DECLARE
obj record;
BEGIN
-- postgresql 9.5 or later:
-- FOR obj in SELECT table_name FROM pg_event_trigger_ddl_commands() WHERE command_tag='CREATE TABLE'
FOR obj IN SELECT tablename FROM pg_tables WHERE tableowner = current_user LOOP
EXECUTE format('ALTER TABLE %s OWNER TO my_group', obj.tablename);
END LOOP;
END;
$$;
CREATE EVENT TRIGGER trg_create_set_owner
ON ddl_command_end
WHEN tag IN ('CREATE TABLE', 'CREATE TABLE AS')
EXECUTE PROCEDURE trg_create_set_owner();
Guess, I should answer this question properly and not just in an edit:
What I want is currently not possible. Perhaps a future update to Postgres will add more functionality to eventtriggers.
Sources:
http://www.postgresql.org/docs/current/static/sql-createeventtrigger.html
http://www.postgresql.org/docs/current/static/plpgsql-trigger.html
How to get the name of the altered table in a Postgres event trigger?
How to get SQL text from Postgres event trigger
I have two similar schemas in a single database with the same function names.
Each schema is owned by a role that matches the schema name.
I have issues about function name resolution with nested functions.
I was expecting that the outer function would call inner functions within the same schema, but it does not!
The name is resolved dynamically based on the search_path at run time which make some sens, but not as I would.
Here is a test case. Let say for example that the schemas and roles are named test and prod as follow.
Test schema:
CREATE ROLE test NOLOGIN;
CREATE SCHEMA test AUTHORIZATION test;
CREATE OR REPLACE FUNCTION test.inner_func() RETURNS TEXT
AS $BODY$
BEGIN
RETURN 'test function';
END
$BODY$ LANGUAGE 'plpgsql';
ALTER FUNCTION test.inner_func() OWNER TO test;
CREATE OR REPLACE FUNCTION test.outer_func() RETURNS SETOF TEXT
AS $BODY$
BEGIN
RETURN QUERY SELECT inner_func();
END
$BODY$ LANGUAGE 'plpgsql';
ALTER FUNCTION test.outer_func() OWNER TO test;
Prod schema:
CREATE ROLE prod NOLOGIN;
CREATE SCHEMA prod AUTHORIZATION prod;
CREATE OR REPLACE FUNCTION prod.inner_func() RETURNS TEXT
AS $BODY$
BEGIN
RETURN 'prod function';
END
$BODY$ LANGUAGE 'plpgsql';
ALTER FUNCTION prod.inner_func() OWNER TO prod;
CREATE OR REPLACE FUNCTION prod.outer_func() RETURNS SETOF TEXT
AS $BODY$
BEGIN
RETURN QUERY SELECT inner_func();
END
$BODY$ LANGUAGE 'plpgsql';
ALTER FUNCTION prod.outer_func() OWNER TO prod;
Test cases:
SET search_path=test,public;
SELECT outer_func();
> test function
SELECT prod.outer_func();
> test function <<<---- was expecting prod function
SET search_path=prod,public;
SELECT prod.outer_func();
> prod function
The test shows that function names are resolved dynamically based on the search_path at run time. Is there a way to bind inner function within the scope of a schema?
I can get such a behavior by using SECURITY DEFINER functions with dynamic SQL and CURRENT_USER, but I am looking for something more straightforward.
The clean solution is to either schema-qualify the function:
CREATE OR REPLACE FUNCTION test.outer_func()
RETURNS SETOF text AS
$func$
BEGIN
RETURN QUERY SELECT test.inner_func();
END
$func$ LANGUAGE plpgsql; -- no quotes!
Or you explicitly set the search_path per function. You can set configuration parameters this way:
CREATE OR REPLACE FUNCTION test.outer_func()
RETURNS SETOF text AS
$func$
BEGIN
RETURN QUERY SELECT inner_func();
END
$func$ LANGUAGE plpgsql SET search_path = test, pg_temp;
Customize the search_path to your needs, possibly add public to the list. I put pg_temp at the end, so objects in the temporary schema cannot hide persisted objects. (But that's not applicable for functions.) Similar to what's explained in the manual for SECURITY DEFINER functions.
I would not advise to rely on the user setting the proper search_path. That would only make sense for "public" functions, it wouldn't be consistent with your design. Why create separate functions and then still have to rely on user settings after all? You could have a single function in the public schema to begin with, but I would not got that route in any case. Very confusing and error prone.
Also, PL/pgSQL executes statements like prepared statements internally. every time you change the search_path, all "prepared" statements from plpgsql functions have to be de-allocated, which is not helping to optimize performance.
Actually, your test case in the question only works if you set the search_path first:
SET search_path=test,public;
Else you get an error when trying to create
CREATE OR REPLACE FUNCTION test.outer_func() RETURNS SETOF TEXT
AS $BODY$
BEGIN
RETURN QUERY SELECT inner_func();
...
ERROR: function inner_func() does not exist
Syntax checks are run against the current search_path at creation time - unless you provide the search_path as suggested. That was fixed 2010 after I reported a bug.
Details for search_path:
How does the search_path influence identifier resolution and the "current schema"
How can I fake inet_client_addr() for unit tests in PostgreSQL?
And don't quote the language name. It's an identifier.
In Postgresql, I have an UPDATE rule on a table which only needs to call a dctUpdate function without doing a whole SQL statement, since the SQL statement is actually done in the function. The only way I know of calling the function is through SELECT dctUpdate(windowId):
create or replace function infoUpdate(windowId in numeric) returns void as $$
begin
if windowId is null then
update info_timestamp set timestamp = now();
else
update info_timestamp set timestamp = now() where window_id = windowId;
end if;
end;
$$ LANGUAGE plpgsql;
create or replace rule info_update_rule as on update to some_table do also select infoUpdate(NEW.window_id);
However, on the command line, when that rule gets triggered because I updated a row in some_table, I get useless output from the SELECT clause that calls the function :
db=# update some_table set name = 'foobar' where window_id = 1;
infoupdate
-----------
(1 row)
UPDATE 1
Is there a way to have info_update_rule call the infoUpdate function without it displaying dummy output?
I've found no options to implement this using rules, but there is an alternative way of implementing this usign triggers.
So, you define trigger function as following:
CREATE OR REPLACE FUNCTION ur_wrapper_trg()
RETURNS trigger AS
$BODY$
begin
perform infoUpdate(NEW.window_id);
RETURN NEW;
end;
$BODY$
LANGUAGE plpgsql VOLATILE
COST 100;
ALTER FUNCTION ur_wrapper_trg() OWNER TO postgres;
Note PERFORM syntax is used. This syntax is identical to SELECT syntax except it supresses all output.
Than you define a trigger
CREATE TRIGGER some_table_utrg
BEFORE UPDATE
ON some_table
FOR EACH ROW
EXECUTE PROCEDURE ur_wrapper_trg();
In the end, you remve your rule.
Haven't tested with null, but with actual windos_ids works as expected, without any unwanted output.
Consult with Triggers and Rules vs triggers for detailed description.
The closes solution to which I came is to call \t \a before select function() and right after it. The only remaining thing is a new line for each call.