Subject: Re: [Proposal] Global temporary tables
To: Pavel Stehule <pavel.stehule@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>,
 Tomas Vondra <tomas.vondra@2ndquadrant.com>,
 =?UTF-8?B?5pu+5paH5peMKOS5ieS7jik=?= <wenjing.zwj@alibaba-inc.com>,
 PostgreSQL Hackers <pgsql-hackers@postgresql.org>, =?UTF-8?B?6JSh5p2+6Zyy?=
 =?UTF-8?B?KOWtkOWYiSk=?= <zijia@taobao.com>, "Cai, Le"
 <le.cai@alibaba-inc.com>, =?UTF-8?B?6JCn5bCR6IGqKOmTgeW6tSk=?=
 <shaocong.xsc@alibaba-inc.com>
References: <24099f4e-742c-e92b-729c-77bac1ca80d4@postgrespro.ru>
 <3fef844f-0e73-8fcb-e4b6-595d6317b191@postgrespro.ru>
 <20200112015109.caab6qdr2ob6d5jv@development>
 <CA+TgmobRhPA1gVbMsj9YLA-sv0Ub8NpMrkWCKwRiD=bnjVND3Q@mail.gmail.com>
 <d2cb4c73-307a-869b-00ae-c1c391cad2b5@postgrespro.ru>
 <CAFj8pRAB4Ni+CL6n9QZ24wdp6n_2TLb2hYm60hs_KVXnDzN8tw@mail.gmail.com>
 <7dd64333-3b6f-5aae-20ac-5fde142902e1@postgrespro.ru>
 <CAFj8pRARb4BiT9Nb-YFg2h+EdbVQt8FY=L0utGM_FL6T-gjc-w@mail.gmail.com>
 <2fd087e8-b03a-5996-e077-df010104177c@postgrespro.ru>
 <CAFj8pRAvegZoQCLw3vjHZ=6_Kr7-1UAA5QgGYOshhXU6j_RuCg@mail.gmail.com>
 <0bddbc6d-fed1-d56b-d39f-67352461b2d1@postgrespro.ru>
 <CAFj8pRDVaNQhg1juJKuj3A2fN-TW5LsMVCqyOkEhKKjbjHEk5w@mail.gmail.com>
 <407d6499-950d-e3d9-acbc-a2e86d8b82a3@postgrespro.ru>
 <CA+TgmobN=o7d4zTJywJzsvkCeL4-_3ttWK_dhzpt-P3yCJ=77w@mail.gmail.com>
 <6cbc12a0-bf0e-0205-959e-d871eb7e7c3e@postgrespro.ru>
 <CAFj8pRB50gSeoNqnkqYkHMN3V74RQFRMPwCkkO9bseFgVLn32Q@mail.gmail.com>
From: Konstantin Knizhnik <k.knizhnik@postgrespro.ru>
Message-ID: <2e7fc7af-34f7-f707-5100-2c3d24128aee@postgrespro.ru>
Date: Wed, 29 Jan 2020 20:21:20 +0300
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101
 Thunderbird/60.2.1
MIME-Version: 1.0
In-Reply-To: 
 <CAFj8pRB50gSeoNqnkqYkHMN3V74RQFRMPwCkkO9bseFgVLn32Q@mail.gmail.com>
Content-Type: multipart/alternative;
 boundary="------------79C2F1A4CD83B54BE160190E"
Content-Language: en-US
Precedence: bulk

This is a multi-part message in MIME format.
--------------79C2F1A4CD83B54BE160190E
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit


On 29.01.2020 20:08, Pavel Stehule wrote:
>
>
>
>     2. Actually I do not propose some completely new approach. I try to
>     provide behavior with is compatible with regular tables.
>     If you create index for regular table, then it can be used in all
>     sessions, right?
>
>
> I don't understand to this point. Regular tables shares data, shares 
> files. You cannot to separate it. More - you have to uses relatively 
> aggressive locks to be this operation safe.
>
> Nothing from these points are valid for GTT.

GTT shares metadata.
As far as them are not sharing data, then GTT are safer than regular 
table, aren't them?
"Safer" means that we need less "aggressive" locks for them: we need to 
protect only metadata, not data itself.

My point is that if we allow other sessions to access created indexes 
for regular tables, then it will be not more complex to support it for GTT.
Actually "not more complex" in this case means "no extra efforts are 
needed".

-- 
Konstantin Knizhnik
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company


--------------79C2F1A4CD83B54BE160190E
Content-Type: text/html; charset=utf-8
Content-Transfer-Encoding: 7bit

<html>
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
  </head>
  <body text="#000000" bgcolor="#FFFFFF">
    <br>
    <br>
    <div class="moz-cite-prefix">On 29.01.2020 20:08, Pavel Stehule
      wrote:<br>
    </div>
    <blockquote type="cite"
cite="mid:CAFj8pRB50gSeoNqnkqYkHMN3V74RQFRMPwCkkO9bseFgVLn32Q@mail.gmail.com">
      <meta http-equiv="content-type" content="text/html; charset=UTF-8">
      <div dir="ltr">
        <div dir="ltr"><br>
        </div>
        <br>
        <div class="gmail_quote"><br>
          <blockquote class="gmail_quote" style="margin:0px 0px 0px
            0.8ex;border-left:1px solid
            rgb(204,204,204);padding-left:1ex">
            2. Actually I do not propose some completely new approach. I
            try to <br>
            provide behavior with is compatible with regular tables.<br>
            If you create index for regular table, then it can be used
            in all <br>
            sessions, right?<br>
          </blockquote>
          <div><br>
          </div>
          <div>I don't understand to this point. Regular tables shares
            data, shares files. You cannot to separate it. More - you
            have to uses relatively aggressive locks to be this
            operation safe. <br>
          </div>
          <div><br>
          </div>
          <div>Nothing from these points are valid for GTT.</div>
        </div>
      </div>
    </blockquote>
    <br>
    GTT shares metadata.<br>
    As far as them are not sharing data, then GTT are safer than regular
    table, aren't them?<br>
    "Safer" means that we need less "aggressive" locks for them: we need
    to protect only metadata, not data itself.<br>
    <br>
    My point is that if we allow other sessions to access created
    indexes for regular tables, then it will be not more complex to
    support it for GTT.<br>
    Actually "not more complex" in this case means "no extra efforts are
    needed".<br>
    <br>
    <pre class="moz-signature" cols="72">-- 
Konstantin Knizhnik
Postgres Professional: <a class="moz-txt-link-freetext" href="http://www.postgrespro.com">http://www.postgrespro.com</a>
The Russian Postgres Company </pre>
  </body>
</html>

--------------79C2F1A4CD83B54BE160190E--