I'm trying to create a postgres function that sends a notification to my C code where the payload string is the current value of a row in a table.
The C side is no problem. I have something like this:
// postgres setup ...
PGnotify *notify = PQnotifies(conn)
printf("Notification: '%s'\n", notify->extra);
I want this to print something like: Notification: MyTable{"ID":123,"Value":9,"Status":false}.
On the Postgres side of things, I can get a particular row as JSON with
select row_to_json(row)
from (
SELECT * FROM "MyTable" WHERE "MyTable"."ID"=123
) row;
But I can't figure out how to do this within a function and save the json result of that select to a local variable. I would expect the following to work ...
do language plpgsql $$
begin
myjson := (select row_to_json(row) from (SELECT * FROM "MyTable" WHERE "MyTable"."ID"=123) row);
-- myrow := ... somehow convert myjson to text ...
-- pg_notify('mychannel', mytable || myrow);
end;
$$;
... but I get the error "myjson is not a known variable". My postgres fu is weak so I'm sure this a simple syntax error but I can't figure it out. I tried 'select into' but couldn't make it work either.
Also, you can see from the commented lines that my intention is to somehow convert that json to text but I'm not sure how to accomplish that.
Any help is appreciated, thanks!
Apparently I needed to declare the variable in it's own block. I guess it handles the text conversion on its own. Also, I had to add perform to the notify command to get it to not complain about an unused result. This is what I ended up with:
do language plpgsql $$
declare
mytable := "MyTable"
myjson text;
begin
myjson := (select row_to_json(row) from (SELECT * FROM "MyTable" WHERE "MyTable"."ID"=123) row);
perform pg_notify('mychannel', mytable||myjson);
end;
$$;
In order to use the variable mytable in the query, I ended up looking at the postgres documentation on Executing Dynamic Commands and finding out I needed to do it this way:
do language plpgsql $$
declare
mytable := "MyTable"
myjson text;
begin
EXECUTE
format('(select row_to_json(row) from (SELECT * FROM %I WHERE %I."ID"=101) row);', mytable, mytable)
INTO myjson;
perform pg_notify('mychannel', mytable||myjson);
end;
$$;
Related
I am trying to fetch data from remote db by using dblink through function but getting an error "query has no destination for result data". I am using plpgsql language to do the same.
Function:
CREATE OR REPLACE FUNCTION fun()
RETURNS text AS
$$
begin
select dblink_connect(
'port=5432 dbname=test user=postgres password=****');
WITH a AS (
SELECT *
FROM dblink(
'SELECT slno,fname,mname,lname
FROM remote_tbl'
) AS t (slno int, fname text, mname text, lname text)
)
, b AS (
INSERT INTO temptab1
SELECT slno, name
FROM a
)
, c AS (
INSERT INTO temptab2
SELECT slno, name
FROM a
)
INSERT INTO temptab3
SELECT slno, name
FROM a;
select dblink_disconnect();
end;
$$
LANGUAGE plpgsql;
Calling Function:
select fun();
Error: query has no destination for result data
The stored procedure won't just return the result of the last SELECT. You need to actually return the value:
CREATE OR REPLACE FUNCTION fun() RETURNS text AS $$
BEGIN
--- ....
RETURN(SELECT dblink_disconnect());
END
$$ LANGUAGE plpgsql;
You're getting the error because Postgres expects the function to return something of type text, but your function doesn't return anything.
Use a plain SQL function instead of PL/PgSQL, or use SELECT INTO and ordinary RETURN.
Reason for the error you're getting is because there is no return in between your BEGIN and END for example:
BEGIN
update mytable set lastcodeused = to_char(cast(lastcodeused as INTEGER)+1, 'FM999999999999999999') where
classid = classIdVar and appid= appIdInt
RETURNING concat(pageUniqueCode,lastcodeused) as pageUniqueCode
into taskcode;
return taskcode;
END;
If you have this error using a pgplsql procedure or function, and you are sure that the return is defined correctly, there exists a different non-intuitive cause. I needed some time to realize this so I think it is worth sharing. I had a function like this:
CREATE OR REPLACE FUNCTION "db".fn_x(
id integer)
RETURNS TABLE(b_val varchar(100), c_val varchar(100))
LANGUAGE 'plpgsql'
AS $BODY$
DECLARE
var_b_val varchar(100);
var_c_val varchar(100);
BEGIN
select var_b, var_c
-- Missing INTO clause was the cause of the error.
var_b_val, var_c_val
from "db".table_y where y_id = id;
return query(select var_b_val, var_c_val);
END;
$BODY$;
Just adding that missing INTO clause made the function work correctly.
In conclusion, this error can also trigger on silent syntax errors.
I'm trying to create a function on PostgreSQL, and I have some problem to use a local variable. Here's my code :
DECLARE query RECORD;
DECLARE schema_name TEXT;
BEGIN
FOR query IN SELECT * FROM context WHERE created_at + make_interval(days => duration) <= CURRENT_TIMESTAMP LOOP
SELECT lower(quote_ident(query.title)) INTO schema_name;
DROP SCHEMA schema_name CASCADE;
DELETE FROM context WHERE id = query.id;
END LOOP;
RETURN 1;
END;
$$ LANGUAGE plpgsql;
The select and delete queries work fine, and I've made a test returning the value of schema_name variable, and it's OK.
My problem is with this line :
DROP SCHEMA schema_name CASCADE;
I get an error as "the schema 'schema_name' doesn't exist".
I'd really appreciate any ideas for how to use this variable to do the drop query.
You need dynamic SQL for this:
DECLARE
query RECORD;
BEGIN
FOR query IN SELECT id, lower(title) as title
FROM context
WHERE created_at + make_interval(days => duration) <= CURRENT_TIMESTAMP
LOOP
execute format('DROP SCHEMA %I CASCADE', query.title);
DELETE FROM context WHERE id = query.id;
END LOOP;
RETURN 1;
END;
$$ LANGUAGE plpgsql;
I also removed the unnecessary SELECT statement to make the title lower case, this is better done in the query directly.
Also: variable assignment is faster with := then with select, so:
schema_name := lower(quote_ident(query.title));
would be better if the variable was needed.
I have an insert trigger function in which NEW.schema_name references a schema. I want to dynamically copy the tables found inside that schema ('foobaz','barbaz') as 'foo' and 'bar'. I then can perform queries without dynamic sql.
How can I create a function or simply copy/paste the same block of code to achive that.
EDIT :
I cannot get that dynamic query to work.
The part inside the WITH statement is working.
Not the bottom 'execute' part. I do not know if it is a syntax problem, or bad cast or whatever constraint there is in pgsql that makes it not working.
WITH info_schema_subset_table as (SELECT table_schema, table_name,
array_to_string((regexp_split_to_array(table_name,'_'))[4:array_length(regexp_split_to_array(table_name,'_'),1)-1] as new_table
FROM information_schema.tables
where table_schema = "schema_searched"
ORDER BY new_table ASC)
EXECUTE 'CREATE TABLE $2 as (SELECT * FROM $1)'
USING info_schema_subset_table.table_schema || '.' ||info_schema_subset_table.table_name,info_schema_subset_table.new_table;
EDIT 2
... Broken code removed...
In the code below, in which I'm unsure if the syntax is right, I get the following from the trigger
Provider errors:
PostGIS error while adding features: ERREUR: l'opérateur n'existe pas : record ~~ unknown
LINE 1: SELECT old_table LIKE '%ens%'
^
HINT: Aucun opérateur ne correspond au nom donné et aux types d'arguments.
Vous devez ajouter des conversions explicites de type.
QUERY: SELECT old_table LIKE '%ens%'
CONTEXT: fonction PL/pgsql validation_sio.afi_validation_sio(), ligne 18 à CASE
EDIT 3 :
CREATE OR REPLACE FUNCTION foo.foo()
RETURNS TRIGGER AS
$BODY$
DECLARE
old_table record;
new_table record;
dynamic_query text;
BEGIN
IF TG_OP = 'INSERT'
THEN
FOR old_table IN SELECT table_schema|| '.' ||table_name
FROM information_schema.tables
where table_schema = NEW.nom_schema
LOOP
CASE
WHEN
old_table LIKE '%ens%' THEN
new_table := concat('SIT_',array_to_string((regexp_split_to_array(info_schema.old_table,'_'))[4:array_length(regexp_split_to_array(info_schema.old_table,'_'),1)-1],'_'));
ELSE
new_table := concat('SID_',array_to_string((regexp_split_to_array(info_schema.old_table,'_'))[4:array_length(regexp_split_to_array(info_schema.old_table,'_'),1)-1],'_'));
END CASE;
dynamic_query := format('SELECT * FROM' || old_table ||);
EXECUTE dynamic_query
INTO new_table;
END LOOP;
RETURN NEW;
END IF;
END;
$BODY$
LANGUAGE plpgsql VOLATILE;
CREATE TRIGGER foo
AFTER INSERT ON validation.validationfoo
FOR EACH ROW EXECUTE PROCEDURE foo.foo();
I've reformatted your trigger function a bit and changed a few things, see if this works.
CREATE OR REPLACE FUNCTION foo.foo()
RETURNS TRIGGER AS
$BODY$
DECLARE
old_table record;
new_table record;
dynamic_query text;
BEGIN
IF TG_OP = 'INSERT' THEN
FOR old_table IN
SELECT table_schema || '.' || table_name AS old_table_name
FROM information_schema.tables
WHERE table_schema = NEW.nom_schema
LOOP
new_table := concat(CASE WHEN old_table.old_table_name LIKE '%ens%' THEN 'SIT_' ELSE 'SID_' END,array_to_string((regexp_split_to_array(info_schema.old_table,'_'))[4:array_length(regexp_split_to_array(info_schema.old_table,'_'),1)-1],'_'));
dynamic_query := 'CREATE TABLE ' || new_table || ' AS SELECT * FROM ' || old_table.old_table_name;
EXECUTE dynamic_query;
END LOOP;
RETURN NEW;
END IF;
END;
$BODY$
LANGUAGE plpgsql VOLATILE;
So the main things:
old_table is a record, so your comparison of it to a string with LIKE was failing. You need to use the field name. So I gave your field a name, and used that field name in the LIKE comparison.
Changed the new_table assignment to put the CASE statement only on the one item that changes, to make the difference more obvious and the code more concise. Mind you, I don't know if the rest of that line is actually valid, I just left it as is.
Changed the creation dynamic_query. As I said in the comment, the format function was being used incorrectly, so I just went with standard string concatenation instead.
Changed dynamic_query's SQL to what I think you actually want it to do. You want it to copy the content of the table to a new table, right? So that will do it.
You cannot have EXECUTE inside an SQL statement, it is a PL/pgSQL statement.
Loop through the tables and issue one EXECUTE for each.
Mind that you cannot have a schema or table name as a parameter with USING, because these names need to be known at parse time.
Use the format function to construct your dynamic statement so you can avoid SQL injection by users who maliciously create tables with weird names.
I am trying to fetch data from remote db by using dblink through function but getting an error "query has no destination for result data". I am using plpgsql language to do the same.
Function:
CREATE OR REPLACE FUNCTION fun()
RETURNS text AS
$$
begin
select dblink_connect(
'port=5432 dbname=test user=postgres password=****');
WITH a AS (
SELECT *
FROM dblink(
'SELECT slno,fname,mname,lname
FROM remote_tbl'
) AS t (slno int, fname text, mname text, lname text)
)
, b AS (
INSERT INTO temptab1
SELECT slno, name
FROM a
)
, c AS (
INSERT INTO temptab2
SELECT slno, name
FROM a
)
INSERT INTO temptab3
SELECT slno, name
FROM a;
select dblink_disconnect();
end;
$$
LANGUAGE plpgsql;
Calling Function:
select fun();
Error: query has no destination for result data
The stored procedure won't just return the result of the last SELECT. You need to actually return the value:
CREATE OR REPLACE FUNCTION fun() RETURNS text AS $$
BEGIN
--- ....
RETURN(SELECT dblink_disconnect());
END
$$ LANGUAGE plpgsql;
You're getting the error because Postgres expects the function to return something of type text, but your function doesn't return anything.
Use a plain SQL function instead of PL/PgSQL, or use SELECT INTO and ordinary RETURN.
Reason for the error you're getting is because there is no return in between your BEGIN and END for example:
BEGIN
update mytable set lastcodeused = to_char(cast(lastcodeused as INTEGER)+1, 'FM999999999999999999') where
classid = classIdVar and appid= appIdInt
RETURNING concat(pageUniqueCode,lastcodeused) as pageUniqueCode
into taskcode;
return taskcode;
END;
If you have this error using a pgplsql procedure or function, and you are sure that the return is defined correctly, there exists a different non-intuitive cause. I needed some time to realize this so I think it is worth sharing. I had a function like this:
CREATE OR REPLACE FUNCTION "db".fn_x(
id integer)
RETURNS TABLE(b_val varchar(100), c_val varchar(100))
LANGUAGE 'plpgsql'
AS $BODY$
DECLARE
var_b_val varchar(100);
var_c_val varchar(100);
BEGIN
select var_b, var_c
-- Missing INTO clause was the cause of the error.
var_b_val, var_c_val
from "db".table_y where y_id = id;
return query(select var_b_val, var_c_val);
END;
$BODY$;
Just adding that missing INTO clause made the function work correctly.
In conclusion, this error can also trigger on silent syntax errors.
I have plpgsql function:
CREATE OR REPLACE FUNCTION test() RETURNS VOID AS
$$
DECLARE
my_row my_table%ROWTYPE;
BEGIN
SELECT * INTO my_row FROM my_table WHERE id='1';
my_row.date := now();
END;
$$ LANGUAGE plpgsql;
I would like to know if it's possible to directly UPDATE my_row record.
The only way I've found to do it now is:
UPDATE my_table SET date=now() WHERE id='1';
Note this is only an example function, the real one is far more complex than this.
I'm using PostgreSQL 9.2.
UPDATE:
Sorry for the confusion, what I wanted to say is:
SELECT * INTO my_row FROM my_table INTO my_row WHERE id='1';
make_lots_of_complicated_modifications_to(my_row, other_complex_parameters);
UPDATE my_row;
I.e. Use my_row to persist information in the underlying table. I have lots of parameters to update.
I would like to know if it's possible to directly update "my_row"
record.
It is.
You can update columns of a row or record type in plpgsql - just like you have it. It should be working, obviously?
This would update the underlying table, of course, not the variable!
UPDATE my_table SET date=now() WHERE id='1';
You are confusing two things here ...
Answer to clarification in comment
I don't think there is syntax in PostgreSQL that can UPDATE a whole row. You can UPDATE a column list, though. Consider this demo:
Note how I use thedate instead of date as column name, date is a reserved word in every SQL standard and a type name in PostgreSQL.
CREATE TEMP TABLE my_table (id serial, thedate date);
INSERT INTO my_table(thedate) VALUES (now());
CREATE OR REPLACE FUNCTION test_up()
RETURNS void LANGUAGE plpgsql AS
$func$
DECLARE
_r my_table;
BEGIN
SELECT * INTO _r FROM my_table WHERE id = 1;
_r.thedate := now()::date + 5 ;
UPDATE my_table t
-- explicit list of columns to be to updated
SET (id, thedate) = (_r.id, _r.thedate)
WHERE t.id = 1;
END
$func$;
SELECT test_up();
SELECT * FROM my_table;
However, you can INSERT a whole row easily. Just don't supply a column list for the table (which you normally should, but in this case it is perfectly ok, not to).
As an UPDATE is internally a DELETE followed by an INSERT anyway, and a function automatically encapsulates everything in a transaction, I don't see, why you couldn't use this instead:
CREATE OR REPLACE FUNCTION x.test_ delins()
RETURNS void LANGUAGE plpgsql AS
$func$
DECLARE
_r my_table;
BEGIN
SELECT * INTO _r
FROM my_table WHERE id = 1;
_r.thedate := now()::date + 10;
DELETE FROM my_table t WHERE t.id = 1;
INSERT INTO my_table SELECT _r.*;
END
$func$;
I managed to get this working in PLPGSQL in a couple of lines of code.
Given a table called table in a schema called example, and a record of the same type declared as _record, you can update all the columns in the table to match the record using the following hack:
declare _record example.table;
...
-- get the columns in the correct order, as a string
select string_agg(format('%I', column_name), ',' order by ordinal_position)
into _columns
from information_schema.columns
where table_schema='example' and table_name='table';
execute 'update example.table set (' || _columns || ') = row($1.*) where pkey=$2'
using _record, _record.pkey;
In the above example, of course, _record.pkey is the table's primary key.
Postgresql has not set row in update.
If you wont update full row you should assign value for each column separately
yes, its possible to update / append the row-type variable,
CREATE OR REPLACE FUNCTION test() RETURNS VOID AS $$
DECLARE
my_row my_table%ROWTYPE;
BEGIN
SELECT * INTO my_row FROM my_table WHERE id='1';
my_row.date := now();
raise notice 'date : %; ',my_row.date;
END;
$$ LANGUAGE plpgsql;
here the raise notice will display the today's date only.
but this will not update the column date in my_table.