Subject: Re: What's the best practice to compare the transaction with the
 checkpoint?
To: Jialun Zhang <reatank@gmail.com>, Laurenz Albe <laurenz.albe@cybertec.at>
Cc: pgsql-novice@lists.postgresql.org
References: 
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 <0bf46f63bd9f7e57a83710644a0ed4cf5f6c52f0.camel@cybertec.at>
 <CAMFL+JjnQE8NWP1vMxfzJXFyjCP-9yvA6ku6FkJAjTpRkOoyTg@mail.gmail.com>
From: Gerald Cheves <gcheves@verizon.net>
Message-ID: <0e86755d-57aa-9c31-31d2-f90b61456c96@verizon.net>
Date: Mon, 6 Jul 2020 10:58:40 -0400
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On 7/6/2020 10:09 AM, Jialun Zhang wrote:
> Thanks! But what I actually mean is how to do this in the backend 
> source code. I think I could find a way to do this SELECT in backend.

What would be the advantage in that method?

>
> Thank you,
> Jialun Zhang
>
> Laurenz Albe <laurenz.albe@cybertec.at 
> <mailto:laurenz.albe@cybertec.at>> 于2020年7月6日周一 上午4:09写道：
>
>     On Sat, 2020-07-04 at 12:19 -0400, Jialun Zhang wrote:
>     > I am trying to add code to determine whether the transaction is
>     checkpointed or not.
>     > So I think I need to compare the transaction ID with the
>     checkpoint's and determine
>     > whether it is older or not. Could anyone tell me what's the best
>     practice of doing
>     > this in Postgres? Is it done somewhere in the existing code?
>
>     You could use
>
>        SELECT next_xid FROM pg_control_checkpoint();
>
>     to get information about the last checkpoint.
>
>     I refrain from asking what the point of the exercise is...
>
>     Yours,
>     Laurenz Albe
>     -- 
>     Cybertec | https://www.cybertec-postgresql.com
>

-- 
siamo arrivati sani e salvi


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    <div class="moz-cite-prefix">On 7/6/2020 10:09 AM, Jialun Zhang
      wrote:<br>
    </div>
    <blockquote type="cite"
cite="mid:CAMFL+JjnQE8NWP1vMxfzJXFyjCP-9yvA6ku6FkJAjTpRkOoyTg@mail.gmail.com">
      <meta http-equiv="content-type" content="text/html; charset=UTF-8">
      <div dir="ltr">Thanks! But what I actually mean is how to do this
        in the backend source code. I think I could find a way to do
        this SELECT in backend.</div>
    </blockquote>
    <p>What would be the advantage in that method?<br>
    </p>
    <blockquote type="cite"
cite="mid:CAMFL+JjnQE8NWP1vMxfzJXFyjCP-9yvA6ku6FkJAjTpRkOoyTg@mail.gmail.com">
      <div dir="ltr">
        <div><br>
        </div>
        <div>Thank you,</div>
        <div>Jialun Zhang</div>
      </div>
      <br>
      <div class="gmail_quote">
        <div dir="ltr" class="gmail_attr">Laurenz Albe &lt;<a
            href="mailto:laurenz.albe@cybertec.at"
            moz-do-not-send="true">laurenz.albe@cybertec.at</a>&gt;
          于2020年7月6日周一 上午4:09写道：<br>
        </div>
        <blockquote class="gmail_quote" style="margin:0px 0px 0px
          0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">On
          Sat, 2020-07-04 at 12:19 -0400, Jialun Zhang wrote:<br>
          &gt; I am trying to add code to determine whether the
          transaction is checkpointed or not.<br>
          &gt; So I think I need to compare the transaction ID with the
          checkpoint's and determine<br>
          &gt; whether it is older or not. Could anyone tell me what's
          the best practice of doing<br>
          &gt; this in Postgres? Is it done somewhere in the existing
          code?<br>
          <br>
          You could use<br>
          <br>
             SELECT next_xid FROM pg_control_checkpoint();<br>
          <br>
          to get information about the last checkpoint.<br>
          <br>
          I refrain from asking what the point of the exercise is...<br>
          <br>
          Yours,<br>
          Laurenz Albe<br>
          -- <br>
          Cybertec | <a href="https://www.cybertec-postgresql.com"
            rel="noreferrer" target="_blank" moz-do-not-send="true">https://www.cybertec-postgresql.com</a><br>
          <br>
        </blockquote>
      </div>
    </blockquote>
    <p><br>
    </p>
    <pre class="moz-signature" cols="72">-- 
siamo arrivati sani e salvi
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