Subject: Re: explain analyze cost
To: pgsql-general@lists.postgresql.org
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From: Ron <ronljohnsonjr@gmail.com>
Message-ID: <01ad39ba-d283-875f-6121-76141a6a4874@gmail.com>
Date: Wed, 12 Dec 2018 16:45:43 -0600
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On 12/12/2018 04:37 PM, Ravi Krishna wrote:
> I am running explain analyze cost on a SQL which reads from two large 
> tables (122mil and 37 mil).  The query is an UPDATE SQL where we use 
> derives table in the from clause and then join it back to the table being 
> updated.
>
> The explain analyze cost itself is taking forever to run. It is running 
> for the last 1 hr. Does that actually run the SQL to find out the impact 
> of I/O (as indicated in COSTS).

Yes.

https://www.postgresql.org/docs/9.6/sql-explain.html

"The ANALYZE option causes the statement to be actually executed, not only 
planned."

> If not, what can cause it to run this slow.
>

-- 
Angular momentum makes the world go 'round.

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    On 12/12/2018 04:37 PM, Ravi Krishna wrote:<br>
    <blockquote type="cite"
cite="mid:1544654267.3583234.1607577016.1555678D@webmail.messagingengine.com">
      <meta http-equiv="content-type" content="text/html; charset=utf-8">
      <title></title>
      <style type="text/css">p.MsoNormal,p.MsoNoSpacing{margin:0}</style>
      <div style="font-family:arial, sans-serif;font-size:16px;">I am
        running explain analyze cost on a SQL which reads from two large
        tables (122mil and 37 mil).  The query is an UPDATE SQL where we
        use derives table in the from clause and then join it back to
        the table being updated.<br>
      </div>
      <div style="font-family:arial, sans-serif;font-size:16px;"><br>
      </div>
      <div style="font-family:arial, sans-serif;font-size:16px;">The
        explain analyze cost itself is taking forever to run. It is
        running for the last 1 hr. Does that actually run the SQL to
        find out the impact of I/O (as indicated in COSTS). </div>
    </blockquote>
    <br>
    Yes.<br>
    <br>
    <a class="moz-txt-link-freetext" href="https://www.postgresql.org/docs/9.6/sql-explain.html">https://www.postgresql.org/docs/9.6/sql-explain.html</a><br>
    <br>
    "The ANALYZE option causes the statement to be actually executed,
    not only planned."<br>
    <br>
    <blockquote type="cite"
cite="mid:1544654267.3583234.1607577016.1555678D@webmail.messagingengine.com">
      <div style="font-family:arial, sans-serif;font-size:16px;">If not,
        what can cause it to run this slow.<br>
      </div>
      <div style="font-family:arial, sans-serif;font-size:16px;"><br>
      </div>
    </blockquote>
    <br>
    <div class="moz-signature">-- <br>
      Angular momentum makes the world go 'round.</div>
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