Revise handling of index-type-specific indexscan cost estimation, per

pghackers discussion of 5-Jan-2000.  The amopselect and amopnpages
estimators are gone, and in their place is a per-AM amcostestimate
procedure (linked to from pg_am, not pg_amop).

2 files changed, 9 insertions, 26 deletions

diff --git a/doc/src/sgml/catalogs.sgml b/doc/src/sgml/catalogs.sgml
index cc28888efeb..d0edf22daa8 100644
--- a/doc/src/sgml/catalogs.sgml
+++ b/doc/src/sgml/catalogs.sgml
@@ -1,6 +1,6 @@
 .\" This is -*-nroff-*-
 .\" XXX standard disclaimer belongs here....
-.\" $Header: /cvsroot/pgsql/doc/src/sgml/catalogs.sgml,v 2.2 2000/01/11 01:40:04 tgl Exp $
+.\" $Header: /cvsroot/pgsql/doc/src/sgml/catalogs.sgml,v 2.3 2000/01/22 23:50:08 tgl Exp $
 .TH "SYSTEM CATALOGS" INTRO 03/13/94 PostgreSQL PostgreSQL
 .SH "Section 7 - System Catalogs"
 .de LS
@@ -138,6 +138,8 @@ pg_am
     regproc     ambuild	/* "build new index" function */
     regproc     amcreate 	/* - deprecated */
     regproc     amdestroy	/* - deprecated */
+    regproc     amcostestimate	/* estimate cost of an indexscan */
+	
 .fi
 .nf M
 pg_amop
@@ -148,10 +150,6 @@ pg_amop
     oid         amopopr	/* the operator */
     int2        amopstrategy	/* traversal/search strategy number
 				   to which this operator applies */
-    regproc     amopselect	/* function to calculate the operator
-				   selectivity */
-    regproc     amopnpages	/* function to calculate the number of
-				   pages that will be examined */
 .fi
 .nf M
 pg_amproc
diff --git a/doc/src/sgml/xindex.sgml b/doc/src/sgml/xindex.sgml
index 771c30e4858..e4d36e1cc5b 100644
--- a/doc/src/sgml/xindex.sgml
+++ b/doc/src/sgml/xindex.sgml
@@ -1,5 +1,5 @@
 <!--
-$Header: /cvsroot/pgsql/doc/src/sgml/xindex.sgml,v 1.5 1999/07/22 15:11:05 thomas Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/xindex.sgml,v 1.6 2000/01/22 23:50:08 tgl Exp $
 Postgres documentation
 -->
 
@@ -403,20 +403,9 @@ CREATE OPERATOR = (
        <entry>the <filename>oid</filename>s of the  operators  for the opclass
 	(which we'll get in just a minute)</entry>
       </row>
-      <row>
-       <entry>amopselect, amopnpages</entry>
-       <entry>cost functions</entry>
-      </row>
      </tbody>
     </tgroup>
    </table>
-
-   The cost functions are used by the query optimizer to decide whether or
-   not to use a given index in a scan.  Fortunately, these already exist.
-   The two functions we'll use are <filename>btreesel</filename>, which
-   estimates the selectivity of the <acronym>B-tree</acronym>, and
-   <filename>btreenpage</filename>, which estimates the number of pages a
-   search will touch in the tree.
   </para>
 
   <para>
@@ -460,10 +449,8 @@ CREATE OPERATOR = (
    equal, in <filename>pg_amop</filename>.  We add the instances we need:
 
    <programlisting>
-    INSERT INTO pg_amop (amopid, amopclaid, amopopr, amopstrategy,
-                amopselect, amopnpages) 
-        SELECT am.oid, opcl.oid, c.opoid, 1,
-                'btreesel'::regproc, 'btreenpage'::regproc
+    INSERT INTO pg_amop (amopid, amopclaid, amopopr, amopstrategy)
+        SELECT am.oid, opcl.oid, c.opoid, 1
         FROM pg_am am, pg_opclass opcl, complex_abs_ops_tmp c
         WHERE amname = 'btree' AND
             opcname = 'complex_abs_ops' AND
@@ -519,13 +506,11 @@ CREATE OPERATOR = (
 
   <para>
    Now we need to add a hashing strategy to allow the type to be indexed.
-   We do this by using another type in pg_am but we reuse the sames ops.
+   We do this by using another type in pg_am but we reuse the same ops.
 
    <programlisting>
-    INSERT INTO pg_amop (amopid, amopclaid, amopopr, amopstrategy,
-                amopselect, amopnpages)
-        SELECT am.oid, opcl.oid, c.opoid, 1,
-                'hashsel'::regproc, 'hashnpage'::regproc
+    INSERT INTO pg_amop (amopid, amopclaid, amopopr, amopstrategy)
+        SELECT am.oid, opcl.oid, c.opoid, 1
         FROM pg_am am, pg_opclass opcl, complex_abs_ops_tmp c
         WHERE amname = 'hash' AND
             opcname = 'complex_abs_ops' AND