#POSTGRESQL ADD FOREIGN KEY UPDATE#

Produce an error indicating that the deletion or update would create a foreign key constraint violation. The On Delete and On Update drop-down list define the type of the actions to be taken. To include field(s)/referenced field(s) to the key, just simply double-click the Fields/ Referenced Fields field or click to open the editor(s) for editing. Use the Referenced Schema and Referenced Table drop-down lists to select a foreign schema and table respectively. In a subsequent post I’ll cover a couple of additional features of those.Use the Name edit box to enter a name for the new key.

In this post I have shown the basics of foreign keys, and how they can be used on partitioned tables just like they can on regular tables. You can do that with the partitioned referencing table easily enough: CREATE INDEX ON stock (item_id)

This is because the server needs to locate those referencing rows in order to know to throw an error or such. In real usage, you would need indexes in the referencing columns in the stock table, if you ever modify the referenced tables. If these examples seem lame to experienced users, it’s because these things work exactly the same for regular (not partitioned) tables since time immemorial. (Of course, an UPDATE operation is for the former operation the same as an INSERT, and for the latter operation the same as a DELETE - meaning that both the original tuple and the modified tuple must be checked, if the UPDATE modifies the columns involved in the foreign key.) INSERT INTO warehouses VALUES (1, 'The moon') ĮRROR: update or delete on table 'warehouses' violates foreign key constraint 'stock_warehouse_id_fkey' on table 'stock'ĭETAIL: Key (warehouse_id)=(1) is still referenced from table 'stock'.ĮRROR: update or delete on table 'items_2' violates foreign key constraint 'stock_item_id_fke圓' on table 'stock'ĭETAIL: Key (item_id)=(1) is still referenced from table 'stock'. After that, a delete in either of the referenced tables will fail, as expected. Then you can insert matching rows in both referenced tables and a referencing row. Second, if you delete a row in either referenced table and there are matching rows in stock, that operation must be rejected too.īoth are easily verified: INSERT INTO stock values (1, 1, 10) ĮRROR: insert or update on table 'stock_0' violates foreign key constraint 'stock_item_id_fkey'ĭETAIL: Key (item_id)=(1) is not present in table 'items'. First, if you insert a row in stock (the referencing table) that doesn’t have a corresponding row in items or warehouses (the referenced table), an error must be raised. There are two basic operations that you want the foreign key to provide. Did you notice that each foreign key is only declared once? One points to to a regular (not partitioned) table warehouses, the other points to partitioned table items. You can see there are two foreign keys here. Warehouse_id integer not null REFERENCES warehouses,ĬREATE TABLE stock_0 PARTITION OF stock FOR VALUES WITH (modulus 5, remainder 0) ĬREATE TABLE stock_1 PARTITION OF stock FOR VALUES WITH (modulus 5, remainder 1) ĬREATE TABLE stock_2 PARTITION OF stock FOR VALUES WITH (modulus 5, remainder 2) ĬREATE TABLE stock_3 PARTITION OF stock FOR VALUES WITH (modulus 5, remainder 3) ĬREATE TABLE stock_4 PARTITION OF stock FOR VALUES WITH (modulus 5, remainder 4) Item_id integer not null REFERENCES items, CREATE TABLE items (ĬREATE TABLE items_0 PARTITION OF items FOR VALUES WITH (modulus 3, remainder 0) ĬREATE TABLE items_1 PARTITION OF items FOR VALUES WITH (modulus 3, remainder 1) ĬREATE TABLE items_2 PARTITION OF items FOR VALUES WITH (modulus 3, remainder 2) ĬREATE TABLE warehouses (warehouse_id integer primary key, location text not null) Now that this feature is complete, some new use cases are open to PostgreSQL that previously weren’t. All this means that for the first time it is possible in PostgreSQL to maintain large volumes of data while maintaining referential integrity. Second, because the (early days) table inheritance feature didn’t really support foreign keys either. Why do I point this out? Two reasons: first, when partitioned tables were first introduced in PostgreSQL 10, they didn’t support foreign keys at all you couldn’t create FKs on partitioned tables, nor create FKs that referenced a partitioned table. You can have a partitioned table on either side of a foreign key constraint, and everything will work correctly.

Now that PostgreSQL 12 is out, we consider foreign keys to be fully compatible with partitioned tables.

PostgreSQL 9 Cookbook – Chinese Edition.

PostgreSQL Server Programming Cookbook – 2nd Edition.

PostgreSQL 9 Administration Cookbook – 3rd Edition.

PostgreSQL High Availability Cookbook – 2nd Edition.

Postgresql add foreign key