Clean up code associated with updating pg_class statistics columns

(relpages/reltuples).  To do this, create formal support in heapam.c for
"overwrite" tuple updates (including xlog replay capability) and use that
instead of the ad-hoc overwrites we'd been using in VACUUM and CREATE INDEX.
Take the responsibility for updating stats during CREATE INDEX out of the
individual index AMs, and do it where it belongs, in catalog/index.c.  Aside
from being more modular, this avoids having to update the same tuple twice in
some paths through CREATE INDEX.  It's probably not measurably faster, but
for sure it's a lot cleaner than before.

1 files changed, 4 insertions, 2 deletions

diff --git a/doc/src/sgml/indexam.sgml b/doc/src/sgml/indexam.sgml
index 01381ff7058..61956cdfcf5 100644
--- a/doc/src/sgml/indexam.sgml
+++ b/doc/src/sgml/indexam.sgml
@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/indexam.sgml,v 2.10 2006/05/02 22:25:09 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/indexam.sgml,v 2.11 2006/05/10 23:18:38 tgl Exp $ -->
 
 <chapter id="indexam">
  <title>Index Access Method Interface Definition</title>
@@ -144,7 +144,7 @@
 
   <para>
 <programlisting>
-void
+IndexBuildResult *
 ambuild (Relation heapRelation,
          Relation indexRelation,
          IndexInfo *indexInfo);
@@ -155,6 +155,8 @@ ambuild (Relation heapRelation,
    in the table.  Ordinarily the <function>ambuild</> function will call
    <function>IndexBuildHeapScan()</> to scan the table for existing tuples
    and compute the keys that need to be inserted into the index.
+   The function must return a palloc'd struct containing statistics about
+   the new index.
   </para>
 
   <para>