Add an EXPLAIN (BUFFERS) option to show buffer-usage statistics.

This patch also removes buffer-usage statistics from the track_counts
output, since this (or the global server statistics) is deemed to be a better
interface to this information.

Itagaki Takahiro, reviewed by Euler Taveira de Oliveira.

1 files changed, 20 insertions, 2 deletions

diff --git a/doc/src/sgml/ref/explain.sgml b/doc/src/sgml/ref/explain.sgml
index 4de5a4aba63..2f6aaf427a8 100644
--- a/doc/src/sgml/ref/explain.sgml
+++ b/doc/src/sgml/ref/explain.sgml
@@ -1,5 +1,5 @@
 <!--
-$PostgreSQL: pgsql/doc/src/sgml/ref/explain.sgml,v 1.47 2009/12/11 01:33:35 adunstan Exp $
+$PostgreSQL: pgsql/doc/src/sgml/ref/explain.sgml,v 1.48 2009/12/15 04:57:47 rhaas Exp $
 PostgreSQL documentation
 -->
 
@@ -31,7 +31,7 @@ PostgreSQL documentation
 
  <refsynopsisdiv>
 <synopsis>
-EXPLAIN [ ( { ANALYZE <replaceable class="parameter">boolean</replaceable> | VERBOSE <replaceable class="parameter">boolean</replaceable> | COSTS <replaceable class="parameter">boolean</replaceable> | FORMAT { TEXT | XML | JSON | YAML } } [, ...] ) ] <replaceable class="parameter">statement</replaceable>
+EXPLAIN [ ( { ANALYZE <replaceable class="parameter">boolean</replaceable> | VERBOSE <replaceable class="parameter">boolean</replaceable> | COSTS <replaceable class="parameter">boolean</replaceable> | BUFFERS <replaceable class="parameter">boolean</replaceable> | FORMAT { TEXT | XML | JSON | YAML } } [, ...] ) ] <replaceable class="parameter">statement</replaceable>
 EXPLAIN [ ANALYZE ] [ VERBOSE ] <replaceable class="parameter">statement</replaceable>
 </synopsis>
  </refsynopsisdiv>
@@ -140,6 +140,24 @@ ROLLBACK;
    </varlistentry>
 
    <varlistentry>
+    <term><literal>BUFFERS</literal></term>
+    <listitem>
+     <para>
+      Include information on buffer usage. Specifically, include the number of
+      shared blocks hits, reads, and writes, the number of local blocks hits,
+      reads, and writes, and the number of temp blocks reads and writes.
+      Shared blocks, local blocks, and temp blocks contain tables and indexes,
+      temporary tables and temporary indexes, and disk blocks used in sort and
+      materialized plans, respectively. The number of blocks shown for an
+      upper-level node includes those used by all its child nodes.  In text
+      format, only non-zero values are printed.  This parameter may only be
+      used with <literal>ANALYZE</literal> parameter.  It defaults to
+      <literal>FALSE</literal>.
+     </para>
+    </listitem>
+   </varlistentry>
+
+   <varlistentry>
     <term><literal>FORMAT</literal></term>
     <listitem>
      <para>