@@ -697,15 +697,6 @@ CREATE INDEX test1_lower_col1_idx ON test1 (lower(col1));
697697</programlisting>
698698 </para>
699699
700- <para>
701- Expression indexes also allow control over the scope of unique indexes.
702- For example, this unique index prevents duplicate integer values from
703- being stored in a <type>double precision</type>-typed column:
704- <programlisting>
705- CREATE UNIQUE INDEX test1_uniq_int ON tests ((floor(double_col)))
706- </programlisting>
707- </para>
708-
709700 <para>
710701 If we were to declare this index <literal>UNIQUE</literal>, it would prevent
711702 creation of rows whose <literal>col1</literal> values differ only in case,
@@ -943,18 +934,11 @@ CREATE UNIQUE INDEX tests_success_constraint ON tests (subject, target)
943934 WHERE success;
944935</programlisting>
945936 This is a particularly efficient approach when there are few
946- successful tests and many unsuccessful ones.
937+ successful tests and many unsuccessful ones. It is also possible to
938+ allow only one null in a column by creating a unique partial index
939+ with an <literal>IS NULL</literal> restriction.
947940 </para>
948941
949- <para>
950- This index allows only one null in the indexed column by using a
951- partial index clause to process only null column values, and using
952- an expression index clause to index <literal>true</literal> instead
953- of <literal>null</literal>:
954- <programlisting>
955- CREATE UNIQUE INDEX tests_target_one_null ON tests ((target IS NULL)) WHERE target IS NULL;
956- </programlisting>
957- </para>
958942 </example>
959943
960944 <para>