Subject: Re: more detailed description of tup_returned and tup_fetched
To: Fujii Masao <masao.fujii@oss.nttdata.com>, pgsql-docs@lists.postgresql.org
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From: Masahiro Ikeda <ikedamsh@oss.nttdata.com>
Message-ID: <e50ffb9e-153f-cb1a-3e59-7edee60941cc@oss.nttdata.com>
Date: Thu, 20 May 2021 17:38:44 +0900
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On 2021/05/20 17:00, Fujii Masao wrote:
> On 2021/05/20 9:46, Masahiro Ikeda wrote:
>> On 2021/05/18 20:10, Fujii Masao wrote:
>>>>> pg_stat_database.tup_fetched:
>>>>> Number of index entries returned by scans on indexes in this database
>>>> Is this the sum of pg_stat_all_indexes.idx_tup_read? This is accounted to
>>>> pg_stat_database.tup_returned.
>>>
>>> I was thinking that pg_stat_database.tup_fetched is the same as
>>> the sum of pg_stat_all_tables.idx_tup_fetch. Because they both
>>> are incremented by bitmap index scans, but pg_stat_all_indexes.idx_tup_read
>>> is not.
>>
>> Yes. So, "Number of index entries returned by scans on indexes in this
>> database" is incorrect, and "Number of live rows fetched by index scans in
>> this database" is correct?
> 
> Yes, I think so!

Thanks!
I updated the patch for summarizing this thread.

Regards,
-- 
Masahiro Ikeda
NTT DATA CORPORATION

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diff --git a/doc/src/sgml/monitoring.sgml b/doc/src/sgml/monitoring.sgml
index dcbb10fb6f..09a22a43ac 100644
--- a/doc/src/sgml/monitoring.sgml
+++ b/doc/src/sgml/monitoring.sgml
@@ -3712,7 +3712,7 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
        <structfield>tup_returned</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of rows returned by queries in this database
+       Number of live rows fetched by sequential scans and index entries returned by index scans in this database
       </para></entry>
      </row>
 
@@ -3721,7 +3721,7 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
        <structfield>tup_fetched</structfield> <type>bigint</type>
       </para>
       <para>
-       Number of rows fetched by queries in this database
+       Number of live rows fetched by index scans in this database
       </para></entry>
      </row>
 

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