From 8aaa04b32d790da595684de58ae4fc2db96becff Mon Sep 17 00:00:00 2001
From: Andres Freund <andres@anarazel.de>
Date: Thu, 30 Mar 2023 19:22:40 -0700
Subject: Track shared buffer hits in pg_stat_io

Among other things, this should make it easier to calculate a useful cache hit
ratio by excluding buffer reads via buffer access strategies. As buffer access
strategies reuse buffers (and thus evict the prior buffer contents), it is
normal to see reads on repeated scans of the same data.

Author: Melanie Plageman <melanieplageman@gmail.com>
Reviewed-by: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/CAAKRu_beMa9Hzih40%3DXPYqhDVz6tsgUGTrhZXRo%3Dunp%2Bszb%3DUA%40mail.gmail.com
---
 doc/src/sgml/monitoring.sgml | 11 +++++++++++
 1 file changed, 11 insertions(+)

(limited to 'doc/src')

diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index c809ff1ba4a..d5a45f996d0 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -3855,6 +3855,17 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
       </entry>
      </row>
 
+     <row>
+      <entry role="catalog_table_entry">
+       <para role="column_definition">
+        <structfield>hits</structfield> <type>bigint</type>
+       </para>
+       <para>
+        The number of times a desired block was found in a shared buffer.
+       </para>
+      </entry>
+     </row>
+
      <row>
       <entry role="catalog_table_entry">
        <para role="column_definition">
-- 
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