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From: Drouvot, Bertrand <[email protected]>
To: Michael Paquier <[email protected]>
To: Kyotaro Horiguchi <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Subject: Re: Reconcile stats in find_tabstat_entry() and get rid of PgStat_BackendFunctionEntry
Date: Wed, 29 Mar 2023 07:44:20 +0200
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <ZCJ53/[email protected]>
	<[email protected]>
	<ZCKGROQ/[email protected]>
	<[email protected]>
	<[email protected]>

Hi,

On 3/29/23 2:09 AM, Michael Paquier wrote:
> On Tue, Mar 28, 2023 at 05:43:26PM +0900, Kyotaro Horiguchi wrote:
>> No. Fine by me, except that "block read requests" seems to suggest
>> kernel read() calls, maybe because it's not clear whether "block"
>> refers to our buffer blocks or file blocks to me.. If it is generally
>> clear, I'm fine with the proposal.
> 
> Okay.  Would somebody like to draft a patch?

Please find a draft attached.

Regards,

-- 
Bertrand Drouvot
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index c809ff1ba4..ae5d9a0226 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5724,8 +5724,10 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
         <returnvalue>bigint</returnvalue>
        </para>
        <para>
-        Returns the number of buffers fetched for table or index, in the current
-        transaction.
+        Returns the number of block read requests for table or index, in the
+        current transaction. This number minus <function>
+        pg_stat_get_xact_blocks_hit</function> gives the number of kernel
+        <function>read()</function> calls.
        </para></entry>
       </row>
 
@@ -5738,8 +5740,9 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
         <returnvalue>bigint</returnvalue>
        </para>
        <para>
-        Returns the number of buffer hits for table or index, in the current
-        transaction.
+        Returns the number of block read requests for table or index, in the
+        current transaction, found in cache (not triggering kernel
+        <function>read()</function> calls).
        </para></entry>
       </row>
 


Attachments:

  [text/plain] v3-0001-pg_stat_get_xact_blocks_fetched-and_hit-doc.patch (1.2K, ../[email protected]/2-v3-0001-pg_stat_get_xact_blocks_fetched-and_hit-doc.patch)
  download | inline diff:
diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index c809ff1ba4..ae5d9a0226 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -5724,8 +5724,10 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
         <returnvalue>bigint</returnvalue>
        </para>
        <para>
-        Returns the number of buffers fetched for table or index, in the current
-        transaction.
+        Returns the number of block read requests for table or index, in the
+        current transaction. This number minus <function>
+        pg_stat_get_xact_blocks_hit</function> gives the number of kernel
+        <function>read()</function> calls.
        </para></entry>
       </row>
 
@@ -5738,8 +5740,9 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
         <returnvalue>bigint</returnvalue>
        </para>
        <para>
-        Returns the number of buffer hits for table or index, in the current
-        transaction.
+        Returns the number of block read requests for table or index, in the
+        current transaction, found in cache (not triggering kernel
+        <function>read()</function> calls).
        </para></entry>
       </row>
 

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