deactivating/activating constraint

Dear All,
is it possible to temporary deactivate a constraint in PostgreSQL?
There is a constraint that does not allow me to write some data (see
e-mail below). But after all datasets are written the constraint is
valid. So I was wondering wether it is possible to deactivate a
constraint write all records in all tables then activate constraint
again. Somebody told me that it is possible in Oracle.
Thanks a lot in advance
Oleg

> Dear All
> I am PostgreSQL beginner. I am trying to write some values from
> external source table “Table1” (using PostGIS plugin) to 2 destination
> PostgreSQL tables “Table2” and “Table3” that describes relations of data:
>
> Table1:
> | A | B |
> ---------
> | 1 | 1 |
> | 2 | 3 |
> | 3 | 1 |
>
> Table2
> | C |
> -----
> | 1 |
> | 2 |
>
> Table3
> | D | E |
> ---------
> | 1 | 1 | case 1
> | 2 | 3 | case 2
>
> Table3 has constraint:
> FOREIGN KEY E REFERENCES Table2 (C) ON UPDATE NO ACTION ON DELETE
> RESTRICT;
>
> I use updateable view “View1” (due to PostGIS interface) with columns
> “C” and “E” and rule:
> AS ON INSERT TO View1 DO INSTEAD (INSERT INTO Table2 VALUES (NEW.C);
> INSERT INTO Table3 VALUES (NEW.D, NEW.E));
>
> I faced following problem: As it is shown in Table3 while trying to
> write data in case 1 everything works fine, but case 2 is not possible
> due to constraint in Table3. However my aim is to write a column A to
> column C, column A to column D and column B to column E not removing
> constraint for table3. May be there is a way to adjust constraint? Or
> may be to adjust rule somehow to make it to write all data from column
> A to column C first and after that fill in Table3?
> Thanks a lot in advance
> Oleg