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PostgreSQL

Home >PostgreSQL > Posgresql how disable and renable foreign constraints

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I had to recover old table data, to do it quickly that I want to delete first the data contained and load from a backup. Cannot just delete the data because the table was linked with several foreign keys. In this case, the backup data are consistent with all the foreign keys, I just needed to disable the foreign keys temporarily to delete the rows. In PostgreSQL, the command: ALTER TABLE t DISABLE TRIGGER ALL; does not just disable all the triggeres table but also the foreign key constraints
-- Parent referenced table 
pgdb=# create table r (c char primary key );

-- Children referencing table 
pgdb=# create table t (c char primary key );
pgdb=# alter table  t add  FOREIGN KEY (c) REFERENCES r;

-- Due the foreign constraint can  insert on children table(t) only if the value is in the referenced table (r)
pgdb=# insert into r values ('a');
pgdb=# insert into t values ('a');

-- Obviously, cannot insert or delete data not in the parent table
pgdb=#  insert into t values ('b');
ERROR:  insert or update on table "t" violates foreign key constraint "t_c_fkey"
DETAIL:  Key (c)=(b) is not present in table "r".

-- In fact, nor deleting
pgdb=# delete from r;
ERROR:  update or delete on table "r" violates foreign key constraint "t_c_fkey" on table "t"
DETAIL:  Key (c)=(a) is still referenced from table "t".

-- 
pgdb=# ALTER TABLE  r  DISABLE TRIGGER ALL;
ALTER TABLE
pgdb=# delete from r;
DELETE 1

-- don't forget to renable it ...
pgdb=# ALTER TABLE  r  ENABLE TRIGGER ALL ; 




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A good scientist is a person with original ideas.
A good engineer is a person who makes a design that works with as few original ideas as possible. There are no prima donnas in engineering.
Freeman Dyson


A good scientist is a person with original ideas.
A good engineer is a person who makes a design that works with as few original ideas as possible. There are no prima donnas in engineering.
Freeman Dyson




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