Postgresql – Violates foreign key constraint

postgresql

I'm trying to implement the below UML and I can't figure out where my mistake is since I have already place a value into the table.

UML class diagram

-- Schema: public

DROP SCHEMA IF EXISTS public CASCADE;

CREATE SCHEMA public
  AUTHORIZATION postgres;
GRANT ALL ON SCHEMA public TO postgres;
GRANT ALL ON SCHEMA public TO public;
COMMENT ON SCHEMA public IS 'standard public schema';

CREATE TYPE color AS ENUM ('green','black','yellow','grey','blue');
CREATE TYPE arrowtype AS ENUM ('both_arrows','begin_arrow','end_arrow'); 
CREATE TYPE treetype AS ENUM ('orange_tree','apple_tree');
CREATE TYPE linetype AS ENUM ('hairline','solid','dotted','dashed');

CREATE TYPE address AS (
street_name TEXT,
street_no TEXT
);

CREATE TYPE square AS (
row VARCHAR(10),
colmn VARCHAR(10)
);

CREATE TABLE user_table (
username VARCHAR(30) NOT NULL PRIMARY KEY,
password VARCHAR(16),
name     VARCHAR(100),
lastname VARCHAR(100),
telephone VARCHAR(20)[],
address address,
birth_year INTEGER
);

CREATE TABLE GraphPanel (
id SERIAL NOT NULL PRIMARY KEY,
title VARCHAR(255),
creation_date TIMESTAMP,
comments TEXT
);

CREATE TABLE GraphObject (
id SERIAL NOT NULL PRIMARY KEY,
color color,
title VARCHAR(255)
);

CREATE TABLE House (
roof_color color,
roof_height INTEGER,
position square
)INHERITS(GraphObject);

CREATE TABLE Arrow (
arrow_line linetype,
arrow_type arrowtype
)INHERITS(GraphObject);

CREATE TABLE Tree (
position square,
tree_type treetype
)INHERITS(GraphObject);

CREATE TABLE creator (
username VARCHAR(30),
panel INTEGER,
category VARCHAR(50),
FOREIGN KEY (username) REFERENCES user_table(username),
FOREIGN KEY (panel) REFERENCES GraphPanel(id)
);

CREATE TABLE container (
panel  INTEGER,
gobject INTEGER,
FOREIGN KEY (panel) REFERENCES GraphPanel(id),
FOREIGN KEY (gobject) REFERENCES GraphObject(id)
);

-- INSERTING VALUES 

-- Users

INSERT INTO user_table (
    username,
    password,name,
    lastname,
    telephone,
    address,
    birth_year
) VALUES (
    'giannis',
    'thepassword',
    'Giannis',
    'Christofakis',
    '{"6944789333","2831051300"}',
    ROW('Evridikis','7'),
    1985
);

INSERT INTO user_table (
    username,
    password,
    name,
    lastname,
    telephone,
    address,
    birth_year
) VALUES (
    'antonis',
    'psw',
    'Antonis',
    'Papadakis',
    '{"6974246700","2831051312"}',
    ROW('Doukos Mpofor','12'),
    1993
);

INSERT INTO user_table (
    username,
    password,
    name,
    lastname,
    telephone,
    address,
    birth_year
) VALUES (
    'mpampis',
    'thepsw',
    'Mpampis',
    'Theodorou',
    '{"6984652333","284131100"}',
    ROW('Markoy Portaliou','8'),
    1981
);

-- SELECT * FROM user_table;

-- GraphPanels

INSERT INTO GraphPanel (
    title,
    creation_date,
    comments
) VALUES (
    'Platia Sinani',
    '2004-10-19 10:23:54',
    'Diamorfosi ths platias Sinani'
);

INSERT INTO GraphPanel (
    title,
    creation_date,
    comments
) VALUES (
    'Parking TEI',
    '2008-11-04 22:20:01',
    'Apeikonisi parking tou TEI'
);

INSERT INTO GraphPanel (
    title,
    creation_date,
    comments
) VALUES (
    'Perioxh Stavormenou',
    '2011-05-17 18:23:33',
    'Dimhourgeia parkou sth perioxh tou Estavromenou'
);

INSERT INTO GraphPanel (
    title,
    creation_date,
    comments
) VALUES (
    'Odos Panagiotaki',
    '2000-09-22 11:00:33',
    'Kataskeuh gefuras'
);

-- SELECT * FROM GraphPanel;

-- creator

INSERT INTO creator (
    username,
    panel,
    category
) VALUES (
    'giannis',
     1,
    'Diamorfosh'
);

INSERT INTO creator (
    username,
    panel,
    category
) VALUES (
    'mpampis',
     2,
    'Apeikonish'
);

INSERT INTO creator (
    username,
    panel,
    category
) VALUES (
    'antonis',
     3,
    'Kataskeuh'
);

INSERT INTO creator (
    username,
    panel,
    category
) VALUES (
    'giannis',
     4,
    'Kataskeuh'
);

-- SELECT * FROM creator;

-- GraphObjects

-- House

INSERT INTO HOUSE (
    color,
    title,
    roof_color,
    roof_height,
    position
) VALUES (
    'grey',
    'Ate Bank',
    'green',
     6,
     ROW('12','A3')
);

INSERT INTO HOUSE (
    color,
    title,
    roof_color,
    roof_height,
    position
) VALUES (
    'grey',
    'residents house',
    'blue',
     4,
     ROW('23','Y3')
);

INSERT INTO HOUSE (
    color,
    title,
    roof_color,
    roof_height,
    position
) VALUES (
    'blue',
    'Super Market',
    'yellow',
     7,
     ROW('08','L2')
);

-- SELECT * FROM House;

-- Trees

INSERT INTO Tree (
    color,
    title,
    position,
    tree_type
) VALUES (
    'green',
    'valencia',
     ROW('07','L2'),
     'orange_tree'
);

INSERT INTO Tree (
    color,
    title,
    position,
    tree_type
) VALUES (
    'green',
    'mantarinia',
     ROW('18','J2'),
     'orange_tree'
);

INSERT INTO Tree (
    color,
    title,
    position,
    tree_type
) VALUES (
    'green',
    'firikia',
     ROW('03','E1'),
     'apple_tree'
);

-- SELECT * FROM Tree;

INSERT INTO Arrow (
    color,
    title,
    arrow_line,
    arrow_type
) VALUES (
    'black',
    'starting point',
     'solid',
     'begin_arrow'
);

INSERT INTO Arrow (
    color,
    title,
    arrow_line,
    arrow_type
) VALUES (
    'grey',
    'ending way',
     'dashed',
     'end_arrow'
);

INSERT INTO Arrow (
    color,
    title,
    arrow_line,
    arrow_type
) VALUES (
    'black',
    'both ways',
     'dotted',
     'both_arrows'
);

 SELECT * FROM GraphObject order by id;

-- container



INSERT INTO container (
    panel,
    gobject
) VALUES (
     1,
     6
);


SELECT * FROM container;

-- SELECT table_name FROM information_schema.tables WHERE table_schema = 'public';

The error is related to the last portion of the code.

ERROR: insert or update on table "container" violates foreign key
constraint "container_gobject_fkey" DETAIL: Key (gobject)=(6) is not
present in table "graphobject".

********** Error **********

ERROR: insert or update on table "container" violates foreign key
constraint "container_gobject_fkey" SQL state: 23503 Detail: Key
(gobject)=(6) is not present in table "graphobject".

UPDATE

OK I misunderstood inheritance. Can anyone advice me how to implement the contains relationship between GraphPanel and GraphObject,Tree,Arrow,House.

Best Answer

Basically foreign key constraints are not inherited. If you are working with table inheritance you have a few options.

Stop enforcing foreign keys
Use constraint triggers to enforce foreign keys

In most cases you are better off with a single large table and smaller join tables possibly with deferred foreign keys. Unfortunately these are not possible either to fully do the things that table inheritance can do so typically there is going to be at least some custom coding.

EDIT (2012-11-27)

You can set the sequence by a query like

SELECT setval('events_eventid_seq', (SELECT max(eventid) FROM events));

In order to let the sequence produce the next value for eventid, you must not set a value explicitly in your INSERT. If you do, it will take the manually supplied value and won't advance the sequence. This will cause the same unique violation error later.

Regarding ALTER TABLE: as you could see, there is some discrepancy between ALTER TABLE - type does not exists and CREATE TABLE. Are you sure you try this on the same database? I can't remember the older versions, but already 8.3 had the bigserial shorthand (it's not a real type). (Giving it further thought, it is quite possible you can't use it in ALTER TABLE, since it is a shorthand...) You can solve the problem by following the manual:

CREATE SEQUENCE events_eventid_seq;

ALTER TABLE events 
ALTER COLUMN eventid TYPE bigint;

ALTER SEQUENCE events_eventid_seq OWNED BY events.eventid;

SELECT setval('events_eventid_seq', (SELECT max(eventid) FROM events));

PostgreSQL – insert/update violates foreign key constraints

There are a few problems with your tables. I'll try to address the foreign keys first, since you question asked about them :)

But before that, we should realize that the two sets of tables (the first three you created and the second set, which you created after dropping the first set) are the same. Of course, the definition of Table3 in your second attempt has syntax and logical errors, but the basic idea is:

CREATE TABLE table3 (   
  "ID" bigint NOT NULL DEFAULT '0',   
  "DataID" bigint DEFAULT NULL,   
  "Address" numeric(20) DEFAULT NULL,   
  "Data" bigint DEFAULT NULL,
   PRIMARY KEY ("ID"),   
   FOREIGN KEY ("DataID") REFERENCES Table1("DataID") on delete cascade on update cascade,   
   FOREIGN KEY ("Address") REFERENCES Table2("Address") on delete cascade on update cascade
);

This definition tell PostgreSQL roughly the following: "Create a table with four columns, one will be the primary key (PK), the others can be NULL. If a new row is inserted, check DataID and Address: if they contain a non-NULL value (say 27856), then check Table1 for DataID˙and Table2 for Address. If there is no such value in those tables, then return an error." This last point which you've seen first:

ERROR: insert or update on table "Table3" violates foreign key constraint 
    "Table3_DataID_fkey" DETAIL: Key (DataID)=(27856) is not present in table "Table1".

So simple: if there is no row in Table1 where DataID = 27856, then you can't insert that row into Table3.

If you need that row, you should first insert a row into Table1 with DataID = 27856, and only then try to insert into Table3. If this seems to you not what you want, please describe in a few sentences what you want to achieve, and we can help with a good design.

And now about the other problems.

You define your PKs as

CREATE all_your_tables (
    first_column NOT NULL DEFAULT '0',   
    [...]
    PRIMARY KEY ("ID"),

A primary key means that all the items in it are different from each other, that is, the values are UNIQUE. If you give a static DEFAULT (like '0') to a UNIQUE column, you will experience bad surprises all the time. This is what you got in your third error message.

Furthermore, '0' means a text string, but not a number (bigint or numeric in your case). Use simply 0 instead (or don't use it at all, as I written above).

And a last point (I may be wrong here): in Table2, your Address field is set to numeric(20). At the same time, it is the PK of the table. The column name and the data type suggests that this address can change in the future. If this is true, than it is a very bad choice for a PK. Think about the following scenario: you have an address '1234567890454', which has a child in Table3 like

ID        DataID           Address             Data
123       3216547          1234567890454       654897564134569

Now that address happens to change to something other. How do you make your child row in Table3 follow its parent to the new address? (There are solutions for this, but can cause much confusion.) If this is your case, add an ID column to your table, which will not contain any information from the real world, it will simply serve as an identification value (that is, ID) for an address.

UPDATE

Best Answer

Related Solutions

PostgreSQL duplicate key violates unique constraint error

EDIT (2012-11-27)

PostgreSQL – insert/update violates foreign key constraints

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