Hi I am trying to work out how to return a subset of a new row as json to a pg_notify function.
I am currently using
create or replace function public.notify_site()
returns trigger
language plpgsql
as $function$
begin
perform pg_notify('ppsite', row_to_json(NEW)::text);
RETURN new;
END;
$function$;
which works fine returning the entire row of data when the after insert trigger for the table fines, however, what I'm trying to do is return just a subset of NEW rather than the entire thing. It would be really cool if I could return the result of a select on NEW or something similar. Is this possible or does my receiving application need to sort the data out instead?
To be clear, I want to return json with say
NEW.c1, NEW.c2, NEW.c5 rather than the entire row of about 50 values.
Ta.
You can define the projection you want from the NEW record:
CREATE OR REPLACE FUNCTION public.notify_site()
RETURNS trigger
LANGUAGE plpgsql
AS $function$
declare
my_record record;
begin
select NEW.id as id, NEW.some_data as some_data INTO my_record;
perform pg_notify('pp_site', row_to_json(my_record)::text);
return NEW;
end;
$function$
;
Related
I'm trying to create a trigger with a condition. Based on the geom length I want the attribute "nom" (= name) to be written in upper case or lower case.
here's what I have:
CREATE OR REPLACE FUNCTION public.test_upper_lower()
RETURNS trigger AS
$BODY$
BEGIN
NEW.dummy:= (ST_Length(new.geom));
if (SELECT dummy FROM ligne_ligne)>100
then NEW.nom:= LOWER(nom) FROM ligne_ligne;
else NEW.nom:= UPPER(nom) FROM ligne_ligne;
end if;
RETURN NEW;
END;
$BODY$
LANGUAGE plpgsql;
DROP trigger IF EXISTS test_upper_lower on public.ligne_ligne;
CREATE trigger test_upper_lower BEFORE INSERT OR UPDATE on public.ligne_ligne
FOR EACH ROW
EXECUTE PROCEDURE public.test_upper_lower();
With this I have a "more than one row returned by a subquery" error
Based on other questions on this forum I tried it using case instead of if and using when in the trigger itself not the function but neither are working
Any ideas ?
Thanks
You don't need (or can actually) use SELECT statements to access data from the inserted row.
The part SELECT dummy FROM ligne_ligne returns all rows from that table - not just from the one relevant to the trigger.
As you just want to check the value you just calculated, simply use new.dummy at that point:
CREATE OR REPLACE FUNCTION public.test_upper_lower()
RETURNS trigger AS
$BODY$
BEGIN
NEW.dummy:= ST_Length(new.geom);
if new.dummy > 100 then --<< no SELECT necessary
NEW.nom:= LOWER(new.nom); --<< no "FROM", just access the value
else
NEW.nom:= UPPER(new.nom);
end if;
RETURN NEW;
END;
$BODY$
LANGUAGE plpgsql;
I'm learning about Postgresql - I don't have a specific application in mind, but the general idea is to update one column with json and not worry about the rest.
I have a table with a few columns (id, name, amount, json). I would like to update only the json column and have a trigger update the other columns from the json.
For example, if json was set to {"name" = "fred", "amount" = 100}, the trigger would populate the name and amount columns
so far, this works:
create table one(id serial primary key, name text, amount int, data jsonb);
CREATE OR REPLACE FUNCTION test()
RETURNS trigger AS
$$
DECLARE
json_name text = (data -> 'name') from one;
json_amount int = (data -> 'amount') from one;
BEGIN
IF json_name IS DISTINCT FROM OLD.name THEN
UPDATE one SET name = json_name;
END IF;
IF json_amount IS DISTINCT FROM OLD.amount THEN
UPDATE one SET amount = json_amount;
END IF;
RETURN NEW;
END;
$$
LANGUAGE 'plpgsql';
CREATE TRIGGER test_trigger
AFTER INSERT OR UPDATE
OF data ON one
FOR EACH ROW
EXECUTE PROCEDURE test();
I'm trying to do this without declaring any variables. for example, I've tried these:
IF one.data->'name' IS DISTINCT FROM OLD.name THEN
or
IF one.data->'name'::text IS DISTINCT FROM OLD.name THEN
or
IF ((data->'name') from one) IS DISTINCT FROM OLD.name THEN
but none work.
Making such a trigger may be a horrible idea, and that would be nice to know, but I'm mainly interested figuring out this json stuff :)
I've made an example here:
https://dbfiddle.uk/?rdbms=postgres_11&fiddle=92f2e6dd3630c76178ca4cfe4dc30b10
Make it a before trigger and instead of an UPDATE manipulate new.
CREATE OR REPLACE FUNCTION test()
RETURNS trigger
AS
$$
BEGIN
new.name := new.data->'name';
new.amount := new.data->'amount';
RETURN new;
END;
$$
LANGUAGE plpgsql;
CREATE TRIGGER test_trigger
BEFORE INSERT
OR UPDATE
OF data
ON one
FOR EACH ROW
EXECUTE PROCEDURE test();
Although the answer provided by #sticky bit goes into the right direction, it doesn't handle type conversion well.
Here's a version that is better at dealing with empty JSON strings:
CREATE OR REPLACE FUNCTION test()
RETURNS trigger AS
$$
BEGIN
NEW.name := (NEW.data->>'name');
NEW.amount := round((NEW.data->>'amount')::numeric)::int;
RETURN NEW;
END;
$$
LANGUAGE 'plpgsql';
CREATE TRIGGER test_trigger
BEFORE INSERT OR UPDATE
OF data ON one
FOR EACH ROW
EXECUTE PROCEDURE test();
https://dbfiddle.uk/?rdbms=postgres_11&fiddle=15a232d4092e23c7bc0425b849b31976
Please remember that executing multiple UPDATEs inside a trigger function after an original INSERT or UPDATE is going to kill performance.
I am using trigger in Postgres database to call function and send newly inserted row to NodeJs application
CREATE OR REPLACE FUNCTION triggerFunction() RETURNS trigger AS $$
DECLARE
BEGIN
PERFORM pg_notify('tableName', row_to_json(NEW)::text );
RETURN NEW;
END;
$$ LANGUAGE plpgsql;
This returns the whole row in json format. However I need to change one of the column name while this row is returned.
Unfortunately AS keywork doesnt work in the row to json with NEW.COLUMN_NAME AS NEW_COLUMN. How can we achieve the solution for this?
CREATE OR REPLACE FUNCTION triggerFunction() RETURNS trigger AS $$
DECLARE
ret json;
BEGIN
select row_to_json(x) into ret from
(select NEW.abc as def, NEW.jkl, NEW.col3) x;
PERFORM pg_notify('tableName', ret::text );
RETURN NEW;
END;
$$ LANGUAGE plpgsql;
I am writing a simple postgres function. The result of this function should be a row of the "events" table. I have the following:
create or replace function featured_event() returns setof events as
$$
begin
select events.* from events where featured is true;
end
$$ LANGUAGE plpgsql;
I don't want to hardcode the columns, but instead use the structure from the existing table as the return type.
This is not a duplicate of Function with SQL query has no destination for result data as I do not want to use the table result type.
Use SQL function:
create or replace function featured_event() returns setof events as
$$
select events.* from events where featured is true;
$$ LANGUAGE sql;
In plpgsql you should use return query:
create or replace function featured_event_plpgsql() returns setof events as
$$
begin
return query select events.* from events where featured is true;
end;
$$ LANGUAGE plpgsql;
I am trying to increment a serial column after an update. I have written a trigger function to help.
CREATE FUNCTION "public"."update_transaction_id" () RETURNS trigger AS
$BODY$
DECLARE
curr_id integer;
BEGIN
curr_id = nextval(pg_get_serial_sequence('current_table', 'transaction_id'));
NEW.transaction_id = curr_id;
PERFORM SETVAL((SELECT pg_get_serial_sequence('current_table', 'transaction_id')), curr_id + 1, false);
RETURN NEW;
END;
$BODY$ LANGUAGE 'plpgsql' IMMUTABLE CALLED ON NULL INPUT SECURITY INVOKER;
CREATE TRIGGER "trg_update_transaction_id" AFTER UPDATE
ON "current_table" FOR EACH ROW
EXECUTE PROCEDURE "public"."update_transaction_id"();
So the column is transaction_id in the table current_table. The query executes fine and the my update function does run through this trigger. However, the transaction_id column remains the same value. Is there something wrong with this procedure?
There are three errors in your code. First, you use the equality operator = instead of the assignment operator :=. Second, you should not SETVAL the sequence; it knows perfectly well how to maintain itself. Third, this function should be called by a BEFORE UPDATE trigger or the assignment to transaction_id will not persist.
So why not simply:
CREATE FUNCTION update_transaction_id() RETURNS trigger AS $BODY$
BEGIN
NEW.transaction_id := nextval('seq_name');
RETURN NEW;
END;
$BODY$ LANGUAGE 'plpgsql';
You can trivially retrieve the immutable name of the sequence from the table definition, so plug that in straightaway.