l"
ACCESSKEY="N"
>Next</A
></TD
></TR
></TABLE
><HR
ALIGN="LEFT"
WIDTH="100%"></DIV
><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="INDEX-UNIQUE-CHECKS"
>54.5. Index Uniqueness Checks</A
></H1
><P
>   <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> enforces SQL uniqueness constraints
   using <I
CLASS="FIRSTTERM"
>unique indexes</I
>, which are indexes that disallow
   multiple entries with identical keys.  An access method that supports this
   feature sets <TT
CLASS="STRUCTNAME"
>pg_am</TT
>.<TT
CLASS="STR