i have use case where i need to increment the version for individual id by one
CREATE TABLE order (
id BIGSERIAL PRIMARY KEY,
version INT NOT NULL,
);
order with order id 1 can have multiple revision say version 1,2 and 3
and if a new order with some different order id come there revision should again start from 1 and need to be increment by 1 if there is any change .
I know it can be taken care at application/program layer. I want to know if there is any constraint or option at DB layer.
This works for me. (I changed the table name to "orders" and added field1 in order to have field to change)
CREATE TABLE orders (
id BIGSERIAL PRIMARY KEY,
version INT NOT NULL,
field1 VARCHAR
);
CREATE OR REPLACE FUNCTION update_row_version()
RETURNS TRIGGER AS $$
BEGIN
IF row(NEW.version) = row(OLD.version) THEN
NEW.version=(select COALESCE(OLD.version,0)+1 where OLD.id=NEW.id);
RETURN NEW;
ELSE
RETURN OLD;
END IF;
END;
$$ language 'plpgsql';
CREATE TRIGGER update_row_version BEFORE UPDATE ON orders FOR EACH ROW EXECUTE PROCEDURE update_row_version();
Related
Given the following (simplified) schema:
CREATE TABLE period (
id UUID NOT NULL DEFAULT uuid_generate_v4(),
name TEXT
);
CREATE TABLE course (
id UUID NOT NULL DEFAULT uuid_generate_v4(),
name TEXT
);
CREATE TABLE registration (
id UUID NOT NULL DEFAULT uuid_generate_v4(),
period_id UUID NOT NULL REFERENCES period(id),
course_id UUID NOT NULL REFERENCES course(id),
inserted_at timestamptz NOT NULL DEFAULT now()
);
I now want to add a new column client_ref, which identifies a registration unique within a period, but consists of only a 4-character string. I want to use pg_hashids - which requires a unique integer input - to base the column value on.
I was thinking of setting up a trigger on the registration table that runs on inserting a new row. I came up with the following:
CREATE OR REPLACE FUNCTION set_client_ref()
RETURNS trigger
LANGUAGE plpgsql
AS $function$
DECLARE
next_row_number integer;
BEGIN
WITH rank AS (
SELECT
period.id AS period_id,
row_number() OVER (PARTITION BY period.id ORDER BY registration.inserted_at)
FROM
registration
JOIN period ON registration.period_id = period.id ORDER BY
period.id,
row_number
)
SELECT
COALESCE(rank.row_number, 0) + 1 INTO next_row_number
FROM
period
LEFT JOIN rank ON (rank.period_id = period.id)
WHERE
period.id = NEW.period_id
ORDER BY
rank.row_number DESC
LIMIT 1;
NEW.client_ref = id_encode (next_row_number);
RETURN NEW;
END
$function$
;
The trigger is set-up like: CREATE TRIGGER set_client_ref BEFORE INSERT ON registration FOR EACH ROW EXECUTE FUNCTION set_client_ref();
This works as expected when inserting a single row to registration, but if I insert multiple within one statement, they end up having the same client_ref. I can reason about why this happens (the rows don't know about each other's existence, so they assume they're all just next in line when retrieving their row_order), but I am not sure what a way is to prevent this. I tried setting up the trigger as an AFTER trigger, but it resulted in the same (duplicated) behaviour.
What would be a better way to get the lowest possible, unique integer for the rows to be inserted (to base the hash function on) that also works when inserting multiple rows?
I'm using PostgreSQL 8.1.23 on x86_64-redhat-linux-gnu
I have to write a database for reserving seats on language courses and there's a requirement there should be a trigger, which will check whether lector, we're trying to write into new group, has any other group at the same time. I have such table:
CREATE TABLE groups (
group_id serial PRIMARY KEY,
lang varchar(3) NOT NULL,
level varchar(3),
seats int4,
lector int4,
start time,
day varchar(3),
FOREIGN KEY (language) REFERENCES languages(lang) ON UPDATE CASCADE ON DELETE CASCADE,
FOREIGN KEY (lector) REFERENCES lectors(lector_id) ON UPDATE CASCADE ON DELETE SET NULL);
and such trigger:
CREATE FUNCTION if_available () RETURNS trigger AS '
DECLARE
r groups%rowtype;
c groups%rowtype;
BEGIN
FOR r IN SELECT * FROM groups WHERE r.lector=NEW.lector ORDER BY group_id LOOP
IF (r.start = NEW.start AND r.day = NEW.day) THEN
RAISE NOTICE ''Lector already has a group at this time!'';
c = NULL;
EXIT;
ELSE
c = NEW;
END IF;
END LOOP;
RETURN c;
END;
' LANGUAGE 'plpgsql';
CREATE TRIGGER if_available_t
BEFORE INSERT OR UPDATE ON grupy
FOR EACH ROW EXECUTE PROCEDURE if_available();
After inserting the new row to a table groups, eg.:
INSERT groups (lang, level, seats, lector, start, day) values ('ger','A-2',12,2,'11:45','wed');
I get an error like this:
ERROR: null value in column "group_id" violates not-null constraint
Without this trigger everything is OK. Could anybody help me how to make it work?
Finally, I have solved it! After BEGIN there should be c = NEW;, because when table groups is empty at the beginning, FOR loop doesn't run and NULL is returned. Also I have changed the condition in FOR loop for: ...WHERE lector = NEW.lector.... And finally, I have changed the condition in IF for IF (r.group_id <> NEW.group_id AND r.start = NEW.start AND r.day = NEW.day) THEN..., because I haven't wanted to run this trigger before one particular update. Maybe this will be helpful for someone :)
I'm using a link table to represent a many-to-many relationship as follows (slightly modified for my use case from this previous answer):
CREATE TABLE owner(
owner_id uuid DEFAULT gen_random_uuid(),
PRIMARY KEY(owner_id)
);
CREATE TABLE product(
product_id uuid DEFAULT gen_random_uuid(),
owner_id uuid NOT NULL,
PRIMARY KEY(product_id)
FOREIGN KEY(owner_id) REFERENCES owner(owner_id)
);
CREATE TABLE bill(
bill_id uuid DEFAULT gen_random_uuid(),
owner_id uuid NOT NULL,
PRIMARY KEY(bill_id),
FOREIGN KEY(owner_id) REFERENCES owner(owner_id)
);
CREATE TABLE bill_product(
bill_id uuid,
product_id uuid,
PRIMARY KEY(bill_id, product_id),
FOREIGN KEY(bill_id) REFERENCES bill(bill_id),
FOREIGN KEY(product_id) REFERENCES product(bill_id)
);
This will of course allow a given bill to belong to many products and vice versa. However, I am wondering what the best way is to ensure that the bill and product belong to the same owner.
I see two options:
Trigger - Have the owner of the bill and product checked BEFORE INSERT, e.g.
CREATE OR REPLACE FUNCTION verify_bill_product_owner() RETURNS trigger AS $trg$
BEGIN
IF (SELECT owner_id FROM product WHERE product_id = NEW.product_id)
<>
(SELECT owner_id FROM bill WHERE bill_id = NEW.bill_id)
THEN
RAISE EXCEPTION 'bill and product do not belong to different owners';
END IF;
RETURN NEW;
END
$trg$ LANGUAGE plpgsql;
CREATE TRIGGER tr_bill_product_biu
BEFORE INSERT OR UPDATE on bill_product
FOR EACH ROW
EXECUTE PROCECURE verify_bill_product_owner();
Compound foreign key - Add the owner_id to the bill_product table and have something like:
-- ..
owner_id uuid,
FOREIGN KEY(owner_id, bill_id) REFERENCES bill(owner_id, bill_id),
FOREIGN KEY(owner_id, product_id) REFERENCES product(product_id, product_id),
-- ..
I think both would work I'm just wondering which is most idiomatic and which would work best in a multi-client/session environment.
I'm using Postgres 9.4.2 :-)
The compound foreign key is cleaner, but requires more space and may have performance implications when the table gets large. The trigger results in the same effect, but I would rewrite the function as follows:
CREATE OR REPLACE FUNCTION verify_bill_product_owner() RETURNS trigger AS $trg$
BEGIN
PERFORM *
FROM product
JOIN bill USING (owner_id)
WHERE product_id = NEW.product_id AND bill_id = NEW.bill_id;
IF NOT FOUND THEN
RETURN NULL;
ELSE
RETURN NEW;
END IF;
END; $trg$ LANGUAGE plpgsql;
CREATE TABLE test ( id int PRIMARY KEY , name );
CREATE TABLE test1 ( id integer[] REFERENCES test , rollid int );
ERROR: foreign key constraint "test3_id_fkey" cannot be implemented
DETAIL: Key columns "id" and "id" are of incompatible types: integer[] and integer.
after that I try to another way also
CREATE TABLE test1 ( id integer[] , rollid int);
ALTER TABLE test1 ADD CONSTRAINT foreignkeyarray FOREIGN KEY (id) REFERENCES test;
ERROR: foreign key constraint "fkarray" cannot be implemented
DETAIL: Key columns "id" and "id" are of incompatible types: integer[] and integer.
so I try create a foreign key array means it say error. please tell me anyone?
postgresql version is 9.1.
What you're trying to do simply can't be done. At all. No ifs, no buts.
Create a new table, test1_test, containing two fields, test1_id, test_id. Put the foreign keys as needed on that one, and make test1's id an integer.
Using arrays with foreign element keys is usually a sign of incorrect design. You need to do separate table with one to many relationship.
But technically it is possible. Example of checking array values without triggers. One reusable function with paramethers and dynamic sql. Tested on PostgreSQL 10.5
create schema if not exists test;
CREATE OR REPLACE FUNCTION test.check_foreign_key_array(data anyarray, ref_schema text, ref_table text, ref_column text)
RETURNS BOOL
RETURNS NULL ON NULL INPUT
LANGUAGE plpgsql
AS
$body$
DECLARE
fake_id text;
sql text default format($$
select id::text
from unnest($1) as x(id)
where id is not null
and id not in (select %3$I
from %1$I.%2$I
where %3$I = any($1))
limit 1;
$$, ref_schema, ref_table, ref_column);
BEGIN
EXECUTE sql USING data INTO fake_id;
IF (fake_id IS NOT NULL) THEN
RAISE NOTICE 'Array element value % does not exist in column %.%.%', fake_id, ref_schema, ref_table, ref_column;
RETURN false;
END IF;
RETURN true;
END
$body$;
drop table if exists test.t1, test.t2;
create table test.t1 (
id integer generated by default as identity primary key
);
create table test.t2 (
id integer generated by default as identity primary key,
t1_ids integer[] not null check (test.check_foreign_key_array(t1_ids, 'test', 't1', 'id'))
);
insert into test.t1 (id) values (default), (default), (default); --ok
insert into test.t2 (id, t1_ids) values (default, array[1,2,3]); --ok
insert into test.t2 (id, t1_ids) values (default, array[1,2,3,555]); --error
If you are able to put there just values from test.id, then you can try this:
CREATE OR REPLACE FUNCTION test_trigger() RETURNS trigger
LANGUAGE plpgsql AS $BODY$
DECLARE
val integer;
BEGIN
SELECT id INTO val
FROM (
SELECT UNNEST(id) AS id
FROM test1
) AS q
WHERE id = OLD.id;
IF val IS NULL THEN RETURN OLD;
ELSE
RAISE 'Integrity Constraint Violation: ID "%" in Test1', val USING ERRCODE = '23000';
RETURN NULL;
END IF;
END; $BODY$;
-- DROP TRIGGER test_delete_trigger ON test;
CREATE TRIGGER test_delete_trigger BEFORE DELETE OR UPDATE OF id ON test
FOR EACH ROW EXECUTE PROCEDURE test_trigger();
I currently have a parent table:
CREATE TABLE members (
member_id SERIAL NOT NULL, UNIQUE, PRIMARY KEY
first_name varchar(20)
last_name varchar(20)
address address (composite type)
contact_numbers varchar(11)[3]
date_joined date
type varchar(5)
);
and two related tables:
CREATE TABLE basic_member (
activities varchar[3])
INHERITS (members)
);
CREATE TABLE full_member (
activities varchar[])
INHERITS (members)
);
If the type is full the details are entered to the full_member table or if type is basic into the basic_member table. What I want is that if I run an update and change the type to basic or full the tuple goes into the corresponding table.
I was wondering if I could do this with a rule like:
CREATE RULE tuple_swap_full
AS ON UPDATE TO full_member
WHERE new.type = 'basic'
INSERT INTO basic_member VALUES (old.member_id, old.first_name, old.last_name,
old.address, old.contact_numbers, old.date_joined, new.type, old.activities);
... then delete the record from the full_member
Just wondering if my rule is anywhere near or if there is a better way.
You don't need
member_id SERIAL NOT NULL, UNIQUE, PRIMARY KEY
A PRIMARY KEY implies UNIQUE NOT NULL automatically:
member_id SERIAL PRIMARY KEY
I wouldn't use hard coded max length of varchar(20). Just use text and add a check constraint if you really must enforce a maximum length. Easier to change around.
Syntax for INHERITS is mangled. The key word goes outside the parens around columns.
CREATE TABLE full_member (
activities text[]
) INHERITS (members);
Table names are inconsistent (members <-> member). I use the singular form everywhere in my test case.
Finally, I would not use a RULE for the task. A trigger AFTER UPDATE seems preferable.
Consider the following
Test case:
Tables:
CREATE SCHEMA x; -- I put everything in a test schema named "x".
-- DROP TABLE x.members CASCADE;
CREATE TABLE x.member (
member_id SERIAL PRIMARY KEY
,first_name text
-- more columns ...
,type text);
CREATE TABLE x.basic_member (
activities text[3]
) INHERITS (x.member);
CREATE TABLE x.full_member (
activities text[]
) INHERITS (x.member);
Trigger function:
Data-modifying CTEs (WITH x AS ( DELETE ..) are the best tool for the purpose. Requires PostgreSQL 9.1 or later.
For older versions, first INSERT then DELETE.
CREATE OR REPLACE FUNCTION x.trg_move_member()
RETURNS trigger AS
$BODY$
BEGIN
CASE NEW.type
WHEN 'basic' THEN
WITH x AS (
DELETE FROM x.member
WHERE member_id = NEW.member_id
RETURNING *
)
INSERT INTO x.basic_member (member_id, first_name, type) -- more columns
SELECT member_id, first_name, type -- more columns
FROM x;
WHEN 'full' THEN
WITH x AS (
DELETE FROM x.member
WHERE member_id = NEW.member_id
RETURNING *
)
INSERT INTO x.full_member (member_id, first_name, type) -- more columns
SELECT member_id, first_name, type -- more columns
FROM x;
END CASE;
RETURN NULL;
END;
$BODY$
LANGUAGE plpgsql VOLATILE;
Trigger:
Note that it is an AFTER trigger and has a WHEN condition.
WHEN condition requires PostgreSQL 9.0 or later. For earlier versions, you can just leave it away, the CASE statement in the trigger itself takes care of it.
CREATE TRIGGER up_aft
AFTER UPDATE
ON x.member
FOR EACH ROW
WHEN (NEW.type IN ('basic ','full')) -- OLD.type cannot be IN ('basic ','full')
EXECUTE PROCEDURE x.trg_move_member();
Test:
INSERT INTO x.member (first_name, type) VALUES ('peter', NULL);
UPDATE x.member SET type = 'full' WHERE first_name = 'peter';
SELECT * FROM ONLY x.member;
SELECT * FROM x.basic_member;
SELECT * FROM x.full_member;