Restructure pg_opclass, pg_amop, and pg_amproc per previous discussions in

pgsql-hackers.  pg_opclass now has a row for each opclass supported by each
index AM, not a row for each opclass name.  This allows pg_opclass to show
directly whether an AM supports an opclass, and furthermore makes it possible
to store additional information about an opclass that might be AM-dependent.
pg_opclass and pg_amop now store "lossy" and "haskeytype" information that we
previously expected the user to remember to provide in CREATE INDEX commands.
Lossiness is no longer an index-level property, but is associated with the
use of a particular operator in a particular index opclass.

Along the way, IndexSupportInitialize now uses the syscaches to retrieve
pg_amop and pg_amproc entries.  I find this reduces backend launch time by
about ten percent, at the cost of a couple more special cases in catcache.c's
IndexScanOK.

Initial work by Oleg Bartunov and Teodor Sigaev, further hacking by Tom Lane.

initdb forced.

doc/src/sgml/ref/create_index.sgml

@@ -1,5 +1,5 @@
 <!--
-$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_index.sgml,v 1.21 2001/08/06 18:09:45 tgl Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/ref/create_index.sgml,v 1.22 2001/08/21 16:35:59 tgl Exp $
 Postgres documentation
 -->
 
@@ -374,9 +374,8 @@ ERROR: Cannot create index: 'index_name' already exists.
 SELECT am.amname AS acc_method,
        opc.opcname AS ops_name,
        opr.oprname AS ops_comp
-    FROM pg_am am, pg_amop amop,
-         pg_opclass opc, pg_operator opr
-    WHERE amop.amopid = am.oid AND
+    FROM pg_am am, pg_opclass opc, pg_amop amop, pg_operator opr
+    WHERE opc.opcamid = am.oid AND
           amop.amopclaid = opc.oid AND
           amop.amopopr = opr.oid
     ORDER BY acc_method, ops_name, ops_comp