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Disallow referential integrity actions from being deferred; only the

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NO ACTION check is deferrable.  This seems to be a closer approximation
to what the SQL spec says than what we were doing before, and it prevents
some anomalous behaviors that are possible now that triggers can fire
during the execution of PL functions.
Stephan Szabo.
This commit is contained in:
Tom Lane
2004-10-21 21:33:59 +00:00
parent 7627b91cd5
commit 12a47c6aca
4 changed files with 63 additions and 37 deletions
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18
doc/src/sgml/ddl.sgml
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@@ -1,4 +1,4 @@
<!-- $PostgreSQL: pgsql/doc/src/sgml/ddl.sgml,v 1.30 2004/08/08 21:33:11 tgl Exp $ -->
<!-- $PostgreSQL: pgsql/doc/src/sgml/ddl.sgml,v 1.31 2004/10/21 21:33:59 tgl Exp $ -->
<chapter id="ddl">
<title>Data Definition</title>
@@ -940,11 +940,17 @@ CREATE TABLE order_items (
<para>
Restricting and cascading deletes are the two most common options.
<literal>RESTRICT</literal> can also be written as <literal>NO
ACTION</literal> and it's also the default if you do not specify
anything. There are two other options for what should happen with
the foreign key columns when a primary key is deleted:
<literal>RESTRICT</literal> prevents a statement from deleting a
referenced row. <literal>NO ACTION</literal> means that if any
referencing rows still exist when the constraint is checked, an error
is raised; this is the default if you do not specify anything.
(The essential difference between these choices is that
<literal>NO ACTION</literal> allows the check to be deferred until
later in the transaction, whereas <literal>RESTRICT</literal> does not.)
There are two other options:
<literal>SET NULL</literal> and <literal>SET DEFAULT</literal>.
These cause the referencing columns to be set to nulls or default
values, respectively, when the referenced row is deleted.
Note that these do not excuse you from observing any constraints.
For example, if an action specifies <literal>SET DEFAULT</literal>
but the default value would not satisfy the foreign key, the
@@ -964,7 +970,7 @@ CREATE TABLE order_items (
<para>
Finally, we should mention that a foreign key must reference
columns that are either a primary key or form a unique constraint.
columns that either are a primary key or form a unique constraint.
If the foreign key references a unique constraint, there are some
additional possibilities regarding how null values are matched.
These are explained in the reference documentation for