Need information about Foreign Key created Triggers

I created a Foreign Key (REFERENCES) constraint on
a table like this (some columns ommited) :
CREATE TABLE tablename (
id_tablename INTEGER DEFAULT nextval('id_tablename_seq'),
tablename_parent INTEGER CONSTRAINT tablename_parent_fk
REFERENCES tablename (id_tablename),
CONSTRAINT tablename_pk PRIMARY KEY (id_tablename)
);

When I pg_dump, I can see three triggers :
The first calls RI_FKey_check_ins AFTER INSERT OR UPDATE,
the second one calls RI_FKey_noaction_del AFTER DELETE,
the third one calls RI_FKey_noaction_upd AFTER UPDATE.

All the triggers and procedure calls have the same parameters.

I browsed the docs, looked at :
http://techdocs.postgresql.org/techdocs/hackingreferentialintegrity.php

and asked pgsql-docs but I couldn't find what they
really do. Can someone give me information about
those Triggers created for FKey RI ?

Best Regards,

Jean-Francois Leveque

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