Expose track_iotiming data via the statistics collector.

Ants Aasma's original patch to add timing information for buffer I/O
requests exposed this data at the relation level, which was judged too
costly.  I've here exposed it at the database level instead.

2 files changed, 24 insertions, 2 deletions

diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 0a5d519214d..81392997f88 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -4295,8 +4295,11 @@ COPY postgres_log FROM '/full/path/to/logfile.csv' WITH csv;
         default, because it will repeatedly query the operating system for
         the current time, which may cause significant overhead on some
         platforms.  You can use the <xref linkend="pgtesttiming"> tool to
-        measure the overhead of timing on your system.  Only superusers can
-        change this setting.
+        measure the overhead of timing on your system.  Timing information is
+        displayed in <xref linkend="pg-stat-database-view">, in the output of
+        <xref linkend="sql-explain"> when the <literal>BUFFERS</> option is
+        used, and by <xref linkend="pgstatstatements">.  Only superusers can
+        change this setting.  
        </para>
       </listitem>
      </varlistentry>
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index 840e54aef8a..013dd335a4a 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -145,6 +145,11 @@ postgres: <replaceable>user</> <replaceable>database</> <replaceable>host</> <re
   </para>
 
   <para>
+   The parameter <xref linkend="guc-track-iotiming"> enables monitoring
+   of block read and write times.
+  </para>
+
+  <para>
    The parameter <xref linkend="guc-track-functions"> enables tracking of
    usage of user-defined functions.
   </para>
@@ -962,6 +967,20 @@ SELECT pg_stat_get_backend_pid(s.backendid) AS pid,
       the <function>pg_stat_get_db_deadlocks</function> function.</entry>
     </row>
     <row>
+     <entry>block_read_time</entry>
+     <entry><type>bigint</></entry>
+     <entry>Time spent by backends reading data file blocks, in milliseconds.
+      The same value can be returned in microseconds by directly calling
+      the <function>pg_stat_get_db_block_time_read</function> function.</entry>
+    </row>
+    <row>
+     <entry>block_write_time</entry>
+     <entry><type>bigint</></entry>
+     <entry>Time spent by backends writing data file blocks, in milliseconds.
+      The same value can be returned in microseconds by directly calling
+      the <function>pg_stat_get_db_block_time_write</function> function.</entry>
+    </row>
+    <row>
      <entry>stats_reset</entry>
      <entry><type>timestamptz</></entry>
      <entry>The last time the statistics were reset.