Can we create Trigger in HSQL DB, with multiple WHEN clause. Something like this :-
CREATE TRIGGER perosn_trig AFTER UPDATE ON person
REFERENCING NEW AS nwrow OLD as oldrow
FOR EACH ROW
when ( nwrow.person_id>100 )
( insert into TRIGLOG values ('PERSON_more_than_100',nwrow.person_id,SYSDATE) ),
When (nwrow.person_id<=100)
( insert into TRIGLOG values ('PERSON_less_than_100',nwrow.person_id,SYSDATE) )
;
This query gives syntax errors.
What will be correct syntax ?
Currently there is no support for multiple WHEN clauses in a trigger. The WHEN clause is generally used with a simple condition to call the trigger only when necessary.
For more complex conditions use a CASE or IF condition:
CREATE TRIGGER perosn_trig AFTER UPDATE ON person
REFERENCING NEW AS nwrow OLD as oldrow
FOR EACH ROW
BEGIN ATOMIC
IF ( nwrow.person_id>100 ) THEN
insert into TRIGLOG values ('PERSON_more_than_100',nwrow.person_id,SYSDATE);
ELSE
insert into TRIGLOG values ('PERSON_less_than_100',nwrow.person_id,SYSDATE);
END IF;
END
http://hsqldb.org/doc/2.0/guide/sqlroutines-chapt.html#src_psm_conditional
Related
I want to define a table with a constraint.
the data is: "article_name,article_time,start_time,end_time"
for the moment I use this condition:
EXCLUDE USING gist (article_name WITH =,
tsrange(start_time,end_time) WITH &&)
but that means to not take any new row for which the range overlaps
with an existing range with the same article_name, whereas I want to change it to get:
don't take new rows for which article_time is inside an existing range (start_time,end_time),
for the same article_name
How can I declare that please?
Thanks a lot
Due to the fact that you can't use <# or #>, I think you need a trigger here with smth like
IF
(
SELECT count(1)
FROM table_name
WHERE article_name = NEW. article_name
AND NOT tsrange(NEW. start_time,NEW. end_time) <# tsrange(start_time, end_time)
) < 1
THEN
return NEW;
END IF;
I have a trigger AFTER INSERT ON mytable that calls a function
CREATE OR REPLACE FUNCTION myfunction() RETURNS trigger AS
$BODY$
DECLARE
index TEXT;
BEGIN
index := 'myIndex_' || NEW.id2::text;
IF to_regclass(index::cstring) IS NULL THEN
EXECUTE 'CREATE INDEX ' || index || ' ON mytable(id) WITH (FILLFACTOR=100) WHERE id2=' || NEW.id2|| ';';
RAISE NOTICE 'Created new index %',index;
END IF;
RETURN NULL;
END;
$BODY$
LANGUAGE plpgsql VOLATILE
SECURITY DEFINER
COST 100;
ALTER FUNCTION myfunction()
OWNER TO theadmin;
This works wonderfully. For each distinct id2 I create an index. Speeds up relevant queries by a lot.
As mentioned above I trigger this AFTER INSERT ON. Before doing that however I had the trigger set to BEFORE INSERT ON. And the function did some strange things. (Yes, I had changed the RETURN NULL to RETURN NEW)
insert of a new row insert into mytable VALUES(1391, 868, 0.5, 0.5);
creates the corresponding index myIndex_868
the inserted row does not appear in mytable when doing a select :(
trying to insert the same row results in ERROR: duplicate key value violates unique constraint "mytable_pkey" because of course DETAIL: Key (id, id2)=(1391, 868) already exists.
inserting other rows for the same id2 works as expected :)
DELETE FROM mytable WHERE id = 1391 and id2 = 868 does nothing
DROP INDEX myIndex_868; drops the index. And suddenly the initial row that never appeared in the table is suddenly there!
Why does BEFORE INSERT ON behave so differently? Is this a bug in postgres 9.4 or did I overlook something?
Just for completeness' sake:
CREATE TRIGGER mytrigger
AFTER INSERT ON mytable
FOR EACH ROW EXECUTE PROCEDURE myfunction();
vs.
CREATE TRIGGER mytrigger
BEFORE INSERT ON mytable
FOR EACH ROW EXECUTE PROCEDURE myfunction();
I'd argue that this is a bug in PostgreSQL. I could reproduce it with 9.6.
It is clear that the row is not contained in the index as it is created in the BEFORE trigger, but the fact that the index is not updated when the row is inserted is a bug in my opinion.
I have written to pgsql-hackers to ask for an opinion.
But apart from that, I don't see the point of the whole exercise.
Better than creating a gazillion indexes would be to create a single one:
CREATE INDEX ON mytable(id2, id);
I am working on my first DB trigger and having an issue. The trigger involves a case statement and I am getting the error #1054 - Unknown column 'ORDERTYPECODE' in 'field list'.
The ORDERTYPECODE is a column on the table from which the trigger is called. Do I need to define which table the column belongs too?
Here is my code:
CREATE TRIGGER `StartNewIncOrderProcessing` AFTER INSERT ON `T_ORDERS`
FOR EACH ROW CASE WHEN ORDERTYPECODE = 'INC' THEN
INSERT INTO T_INC_DATA (ORDERID) VALUES ((SELECT MAX(ORDERID) FROM T_ORDERS));
END CASE;
Figured it out.
CREATE TRIGGER `StartNewIncOrderProcessing` AFTER INSERT ON `T_ORDERS`
FOR EACH ROW BEGIN
IF NEW.ORDERTYPECODE = 'INC' THEN
INSERT INTO T_INC_DATA (ORDERID)
VALUES ((SELECT MAX(ORDERID) FROM T_ORDERS ));
END IF;
END
I have a URLs table. They contain
(id int primary key,
url character varying unique,
content character varying,
last analyzed date).
I want to create trigger or something(rule may be), so each time i make insert from my java program, it updates some single row if row with such URL exists. Else it should perform an Insert.
Please, can you provide a complete code in Postgresql. Thanks.
This has been asked many times. A possible solution can be found here:
https://stackoverflow.com/a/6527838/552671
This solution requires both an UPDATE and INSERT.
UPDATE table SET field='C', field2='Z' WHERE id=3;
INSERT INTO table (id, field, field2)
SELECT 3, 'C', 'Z'
WHERE NOT EXISTS (SELECT 1 FROM table WHERE id=3);
With Postgres 9.1 it is possible to do it with one query:
https://stackoverflow.com/a/1109198/2873507
If INSERTS are rare, I would avoid doing a NOT EXISTS (...) since it emits a SELECT on all updates. Instead, take a look at wildpeaks answer: https://dba.stackexchange.com/questions/5815/how-can-i-insert-if-key-not-exist-with-postgresql
CREATE OR REPLACE FUNCTION upsert_tableName(arg1 type, arg2 type) RETURNS VOID AS $$
DECLARE
BEGIN
UPDATE tableName SET col1 = value WHERE colX = arg1 and colY = arg2;
IF NOT FOUND THEN
INSERT INTO tableName values (value, arg1, arg2);
END IF;
END;
$$ LANGUAGE 'plpgsql';
This way Postgres will initially try to do a UPDATE. If no rows was affected, it will fall back to emitting an INSERT.
I found this post more relevant in this scenario:
WITH upsert AS (
UPDATE spider_count SET tally=tally+1
WHERE date='today' AND spider='Googlebot'
RETURNING *
)
INSERT INTO spider_count (spider, tally)
SELECT 'Googlebot', 1
WHERE NOT EXISTS (SELECT * FROM upsert)
Firstly It tries insert. If there is a conflict on url column then it updates content and last_analyzed fields. If updates are rare this might be better option.
INSERT INTO URLs (url, content, last_analyzed)
VALUES
(
%(url)s,
%(content)s,
NOW()
)
ON CONFLICT (url)
DO
UPDATE
SET content=%(content)s, last_analyzed = NOW();
create table urls (
url_id serial primary key,
url text unique,
content text,
last_analyzed timestamptz);
insert into urls(url) values('hello'),
('How'),('are'),
('you'),('doing');
By creating procedure, you also also do upsert.
CREATE OR REPLACE PROCEDURE upsert_url(_url text) LANGUAGE plpgsql
as $$
BEGIN
INSERT INTO URLs (url) values (_url)
ON CONFLICT (url)
DO UPDATE SET last_analyzed = NOW();
END
$$;
Test it through call the procedure.
call upsert_url('I am is ok');
call upsert_url('hello');
I have two tables. Lets say tblA and tblB.
I need to insert a row in tblA and use the returned id as a value to be inserted as one of the columns in tblB.
I tried finding out this in documentation but could not get it. Well, is it possible to write a statement (intended to be used in prepared) like
INSERT INTO tblB VALUES
(DEFAULT, (INSERT INTO tblA (DEFAULT, 'x') RETURNING id), 'y')
like we do for SELECT?
Or should I do this by creating a Stored Procedure?. I'm not sure if I can create a prepared statement out of a Stored Procedure.
Please advise.
Regards,
Mayank
You'll need to wait for PostgreSQL 9.1 for this:
with
ids as (
insert ...
returning id
)
insert ...
from ids;
In the meanwhile, you need to use plpgsql, a temporary table, or some extra logic in your app...
This is possible with 9.0 and the new DO for anonymous blocks:
do $$
declare
new_id integer;
begin
insert into foo1 (id) values (default) returning id into new_id;
insert into foo2 (id) values (new_id);
end$$;
This can be executed as a single statement. I haven't tried creating a PreparedStatement out of that though.
Edit
Another approach would be to simply do it in two steps, first run the insert into tableA using the returning clause, get the generated value through JDBC, then fire the second insert, something like this:
PreparedStatement stmt_1 = con.prepareStatement("INSERT INTO tblA VALUES (DEFAULT, ?) returning id");
stmt_1.setString(1, "x");
stmt_1.execute(); // important! Do not use executeUpdate()!
ResultSet rs = stmt_1.getResult();
long newId = -1;
if (rs.next()) {
newId = rs.getLong(1);
}
PreparedStatement stmt_2 = con.prepareStatement("INSERT INTO tblB VALUES (default,?,?)");
stmt_2.setLong(1, newId);
stmt_2.setString(2, "y");
stmt_2.executeUpdate();
You can do this in two inserts, using currval() to retrieve the foreign key (provided that key is serial):
create temporary table tb1a (id serial primary key, t text);
create temporary table tb1b (id serial primary key,
tb1a_id int references tb1a(id),
t text);
begin;
insert into tb1a values (DEFAULT, 'x');
insert into tb1b values (DEFAULT, currval('tb1a_id_seq'), 'y');
commit;
The result:
select * from tb1a;
id | t
----+---
3 | x
(1 row)
select * from tb1b;
id | tb1a_id | t
----+---------+---
2 | 3 | y
(1 row)
Using currval in this way is safe whether in or outside of a transaction. From the Postgresql 8.4 documentation:
currval
Return the value most recently
obtained by nextval for this sequence
in the current session. (An error is
reported if nextval has never been
called for this sequence in this
session.) Because this is returning a
session-local value, it gives a
predictable answer whether or not
other sessions have executed nextval
since the current session did.
You may want to use AFTER INSERT trigger for that. Something along the lines of:
create function dostuff() returns trigger as $$
begin
insert into table_b(field_1, field_2) values ('foo', NEW.id);
return new; --values returned by after triggers are ignored, anyway
end;
$$ language 'plpgsql';
create trigger trdostuff after insert on table_name for each row execute procedure dostuff();
after insert is needed because you need to have the id to reference it. Hope this helps.
Edit
A trigger will be called in the same "block" as the command that triggered it, even if not using transactions - in other words, it becomes somewhat part of that command.. Therefore, there is no risk of something changing the referenced id between inserts.