LI
><P
>        Provide more reliable operation during concurrent
        <ACRONYM
CLASS="ACRONYM"
>DDL</ACRONYM
> (Robert Haas, Noah Misch)
       </P
><P
>        This change adds locking that should eliminate <SPAN
CLASS="QUOTE"
>"cache lookup
        failed"</SPAN
> errors in many scenarios.  Also, it is no longer possible
        to add relations to a schema that is being concurrently dropped, a
        scenario that formerly led to inconsistent system catalog contents.
       </P
></LI
><LI
><P
>     