*** a/doc/src/sgml/ddl.sgml
--- b/doc/src/sgml/ddl.sgml
***************
*** 550,555 **** CREATE TABLE products (
--- 550,563 ----
     </indexterm>
  
     <para>
+     Adding a unique constraint will automatically create a unique btree
+     index on the column or group of columns declared for the constraint.
+     The index name will match the name given to the constraint; if no
+     constraint name is specified, it will be the table name suffixed
+     with <literal>_<replaceable>columnname_key</replaceable></literal>.
+    </para>
+ 
+    <para>
      In general, a unique constraint is violated when there is more than
      one row in the table where the values of all of the
      columns included in the constraint are equal.
***************
*** 623,628 **** CREATE TABLE example (
--- 631,644 ----
     </para>
  
     <para>
+     Adding a primary key will automatically create a unique btree index
+     on the column or group of columns declared for the primary key.
+     The index name will match the name given to the constraint; if no
+     constraint name is specified, it will be the table name suffixed
+     with <literal>_pkey</literal>.
+    </para>
+ 
+    <para>
      A table can have at most one primary key.  (There can be any number
      of unique and not-null constraints, which are functionally the same
      thing, but only one can be identified as the primary key.)
***************
*** 832,837 **** CREATE TABLE order_items (
--- 848,863 ----
     </para>
  
     <para>
+     Since a <command>DELETE</command> of a row from a referenced table
+     or an <command>UPDATE</command> of a referenced column will require
+     a scan of the referencing table for rows matching the old value, it
+     is often a good idea to index the referencing columns.  Because it
+     is not always needed, and there are many choices available on how
+     index, declaration of a foreign key constraint does not
+     automatically create an index.
+    </para>
+ 
+    <para>
      More information about updating and deleting data is in <xref
      linkend="dml">.
     </para>
***************
*** 875,880 **** CREATE TABLE circles (
--- 901,915 ----
      See also <link linkend="SQL-CREATETABLE-EXCLUDE"><command>CREATE
      TABLE ... CONSTRAINT ... EXCLUDE</></link> for details.
     </para>
+ 
+    <para>
+     Adding an exclusion constraint will automatically create an index
+     of the type specified in the constraint declaration.  The index
+     name will match the name given to the constraint; if no constraint
+     name is specified, it will be the table name and column names used
+     in the constraint, separated by underscores, suffixed with
+     <literal>_excl</literal>.
+    </para>
    </sect2>
   </sect1>