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help / color / mirror / Atom feedFrom: Masahiro Ikeda <[email protected]>
To: Fujii Masao <[email protected]>
To: [email protected]
Subject: Re: more detailed description of tup_returned and tup_fetched
Date: Thu, 20 May 2021 17:38:44 +0900
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
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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
Attachments:
[text/x-patch] v1-0002-add-more-detailed-description-of-tup_returned-and-tup_fetched.patch (956B, 2-v1-0002-add-more-detailed-description-of-tup_returned-and-tup_fetched.patch)
download | inline diff:
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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