y indicates that the
       corresponding index attribute is an expression over the table columns,
       rather than a simple column reference.
      </TD
></TR
><TR
><TD
><TT
CLASS="STRUCTFIELD"
>indcollation</TT
></TD
><TD
><TT
CLASS="TYPE"
>oidvector</TT
></TD
><TD
><TT
CLASS="LITERAL"
><A
HREF="catalog-pg-collation.html"
><TT
CLASS="STRUCTNAME"
>pg_collation</TT
></A
>.oid</TT
></TD
><TD
>       For each column in the index key, this contains the OID of the
       collation to use for the index.
      