From: Tatsuro Yamada <tatsuro.yamada.tf@nttcom.co.jp>
Subject: Re: progress report for ANALYZE
References: <20191128133717.GA22933@alvherre.pgsql>
 <5331546a-7ec4-5539-6912-8c13829de1d8@nttcom.co.jp_1>
 <afdbba1d-50ad-bc73-8f29-76e2b6e9d0cb@nttcom.co.jp_1>
 <CA+HiwqEHBiqFyY1_GnqG_6mYTXufMxrrCZhmXUNNeTM7WYkyOQ@mail.gmail.com>
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Date: Wed, 04 Dec 2019 17:53:42 +0900
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To: Amit Langote <amitlangote09@gmail.com>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>,
 vignesh C <vignesh21@gmail.com>,
 Pg Hackers <pgsql-hackers@lists.postgresql.org>
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Hi Amit-san,

Thanks for your comments!

>> Attached patch is the revised patch. :)
>>
>> I wonder two things below. What do you think?
>>
>> 1)
>> For now, I'm not sure it should be set current_child_table_relid to zero
>> when the current phase is changed from "acquiring inherited sample rows" to
>> "computing stats". See <Test result> bellow.
> 
> In the upthread discussion [1], Robert asked to *not* do such things,
> that is, resetting some values due to phase change.  I'm not sure his
> point applies to this case too though.

Yeah, I understood.
I'll check target relid of "computing stats" to re-read a code of
analyze command later. :)

  
>> 2)
>> There are many "finalizing analyze" phases based on relids in the case
>> of partitioning tables. Would it better to fix the document? or it
>> would be better to reduce it to one?
>>
>> <Document>
>> ---------------------------------------------------------
>>        <entry><literal>finalizing analyze</literal></entry>
>>        <entry>
>>          The command is updating pg_class. When this phase is completed,
>>          <command>ANALYZE</command> will end.
>> ---------------------------------------------------------
> 
> When a partitioned table is analyzed, its partitions are analyzed too.
> So, the ANALYZE command effectively runs N + 1 times if there are N
> partitions -- first analyze partitioned table to collect "inherited"
> statistics by collecting row samples using
> acquire_inherited_sample_rows(), then each partition to collect its
> own statistics.  Note that this recursive application to ANALYZE to
> partitions (child tables) only occurs for partitioned tables, not for
> legacy inheritance.

Thanks for your explanation.
I understand Analyzing Partitioned table a little.
Below is my understanding. Is it right?

==================================================
In the case of partitioned table (N = 3)

  - Partitioned table name: p (relid is 100)
  - Partitioning table names: p1, p2, p3 (relids are 201, 202 and 203)

For now, We can get the following results by executing "analyze p;".

Num Phase                         relid current_child_table_relid
  1  acquire inherited sample rows  100   201
  2  acquire inherited sample rows  100   202
  3  acquire inherited sample rows  100   203
  4  computing stats                100   0
  5  finalizing analyze             100   0

  6  acquiring sample rows          201   0
  7  computing stats                201   0
  8  finalizing analyze             201   0

  9  acquiring sample rows          202   0
10  computing stats                202   0
11  finalizing analyze             202   0

12  acquiring sample rows          203   0
13  computing stats                203   0
14  finalizing analyze             203   0
==================================================


Thanks,
Tatsuro Yamada