diff --git a/doc/src/sgml/ddl.sgml b/doc/src/sgml/ddl.sgml
index 9709dd6..09d7a24 100644
*** a/doc/src/sgml/ddl.sgml
--- b/doc/src/sgml/ddl.sgml
*************** ANALYZE measurement;
*** 3021,3030 ****
      <firstterm>foreign data wrapper</firstterm>. A foreign data wrapper is a
      library that can communicate with an external data source, hiding the
      details of connecting to the data source and fetching data from it. There
!     are several foreign data wrappers available, which can for example read
!     plain data files residing on the server, or connect to another PostgreSQL
!     instance. If none of the existing foreign data wrappers suit your needs,
!     you can write your own; see <xref linkend="fdwhandler">.
     </para>
  
     <para>
--- 3021,3031 ----
      <firstterm>foreign data wrapper</firstterm>. A foreign data wrapper is a
      library that can communicate with an external data source, hiding the
      details of connecting to the data source and fetching data from it. There
!     is a foreign data wrapper available as a <file>contrib</file> module,
!     which can read plain data files residing on the server.  Other kind of
!     foreign data wrappers might be found as third party products.  If none of
!     the existing foreign data wrappers suit your needs, you can write your
!     own; see <xref linkend="fdwhandler">.
     </para>
  
     <para>
diff --git a/doc/src/sgml/fdwhandler.sgml b/doc/src/sgml/fdwhandler.sgml
index fc07f12..f1318d7 100644
*** a/doc/src/sgml/fdwhandler.sgml
--- b/doc/src/sgml/fdwhandler.sgml
*************** IterateForeignScan (ForeignScanState *no
*** 180,185 ****
--- 180,193 ----
      </para>
  
      <para>
+      Note that <productname>PostgreSQL</productname>'s executor doesn't care
+      whether the rows returned violate the NOT NULL constraints which were
+      defined on the foreign table columns.  If you want to make the FDW that
+      enforce NOT NULL constraints, you need to raise an error when a result
+      data fetched from the foreign source violates the constraint.
+     </para>
+ 
+     <para>
  <programlisting>
  void
  ReScanForeignScan (ForeignScanState *node);