Content-Type: multipart/alternative;
 boundary="------------qXiBUNN3eSAeS2dDZcafQVSJ"
Message-ID: <7f4f2ef7-460a-4395-bd58-eca4fca7c4c9@gmail.com>
Date: Mon, 29 Apr 2024 21:47:41 +0300
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: Extension Enhancement: Buffer Invalidation in pg_buffercache
From: Maksim Milyutin <milyutinma@gmail.com>
To: Thomas Munro <thomas.munro@gmail.com>, Maxim Orlov <orlovmg@gmail.com>
Cc: vignesh C <vignesh21@gmail.com>,
 Palak Chaturvedi <chaturvedipalak1911@gmail.com>,
 Jim Nasby <jim.nasby@gmail.com>, pgsql-hackers@postgresql.org,
 Nitin Jadhav <nitinjadhavpostgres@gmail.com>
References: <CALfch19pW48ZwWzUoRSpsaV9hqt0UPyaBPC4bOZ4W+c7FF566A@mail.gmail.com>
 <CAMm1aWbk-0C460G9ooy2yNSy1riecqvw4F7jPnqvToFZ_s4oGw@mail.gmail.com>
 <CALfch1890bL5SddyOpZDC8d-jZFOUGCGbOr+_11jLTwwJ_WEOA@mail.gmail.com>
 <CALfch1_s-X3wxeQbYxhXVuWZKBeY5YvU1D+nJxe21ri5iv0qrw@mail.gmail.com>
 <8b8c709a-c7cc-4965-8296-64f549c27501@abcsql.com>
 <3510716d-d3f3-40c8-9f7f-d644171acfb6@gmail.com>
 <a2c3312f-0866-443f-a799-dd76ebf9c7f5@abcsql.com>
 <CALDaNm20+pri5yvEF-4HZqCwRjHB+qjWHLcfanyEjnwgF96z6Q@mail.gmail.com>
 <CA+hUKGL9Y3RgK=SjzSwvUnS4-5RcFEXJ3fwqbLCa9bo8g4uOOg@mail.gmail.com>
 <CACG=ezbBCXaP_KH3N15_tHSwAcCmHQjTyOVsd2o5qG6B_dPzPg@mail.gmail.com>
 <CA+hUKGKGyVjqoaSC7AZrgYKHAk9Nid9G4Ao3ZtL_OtLZDb+_cA@mail.gmail.com>
 <CA+hUKG+CjngU9+7mfPsV6tA8Rze9keoV887mHxUL_9qiFUrjJA@mail.gmail.com>
 <c4e75c92-b63f-4b45-bbcf-dddd601a9451@gmail.com>
Content-Language: en-US
In-Reply-To: <c4e75c92-b63f-4b45-bbcf-dddd601a9451@gmail.com>
Archived-At: <https://www.postgresql.org/message-id/7f4f2ef7-460a-4395-bd58-eca4fca7c4c9%40gmail.com>
Precedence: bulk

This is a multi-part message in MIME format.
--------------qXiBUNN3eSAeS2dDZcafQVSJ
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit

On 14.04.2024 21:16, Maksim Milyutin wrote:

> On 07.04.2024 02:07, Thomas Munro wrote:
>
>> So this is the version I plan to commit.
>>
>> +bool
>> +EvictUnpinnedBuffer(Buffer buf)
>> +{
>> ...
>> +    /* This will return false if it becomes dirty or someone else pins it. */
>> +    result = InvalidateVictimBuffer(desc);
>> +
>> +    UnpinBuffer(desc);
>> +
>> +    return result;
>> +}
>
>
> Hi, Thomas!
>
> Should not we call at the end the StrategyFreeBuffer() function to add 
> target buffer to freelist and not miss it after invalidation?
>

Hello everyone!

Please take a look at this issue, current implementation of 
EvictUnpinnedBuffer() IMO is erroneous - evicted buffers are lost 
permanently and will not be reused again

-- 
Best regards,
Maksim Milyutin

--------------qXiBUNN3eSAeS2dDZcafQVSJ
Content-Type: text/html; charset=UTF-8
Content-Transfer-Encoding: 7bit

<!DOCTYPE html>
<html>
  <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
  </head>
  <body>
    <p>On 14.04.2024 21:16, Maksim Milyutin wrote:</p>
    <blockquote type="cite"
      cite="mid:c4e75c92-b63f-4b45-bbcf-dddd601a9451@gmail.com">
      <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
      <p>On 07.04.2024 02:07, Thomas Munro wrote:</p>
      <div class="moz-cite-prefix"><span style="white-space: pre-wrap">
</span></div>
      <blockquote type="cite"
cite="mid:CA+hUKG+CjngU9+7mfPsV6tA8Rze9keoV887mHxUL_9qiFUrjJA@mail.gmail.com">
        <pre class="moz-quote-pre" wrap="">So this is the version I plan to commit.

+bool
+EvictUnpinnedBuffer(Buffer buf)
+{
...
+    /* This will return false if it becomes dirty or someone else pins it. */
+    result = InvalidateVictimBuffer(desc);
+
+    UnpinBuffer(desc);
+
+    return result;
+}
</pre>
      </blockquote>
      <p><br>
      </p>
      <p>Hi, Thomas!</p>
      <p>Should not we call at the end the StrategyFreeBuffer() function
        to add target buffer to freelist and not miss it after
        invalidation?</p>
    </blockquote>
    <p><br>
    </p>
    <p>Hello everyone!</p>
    <p>Please take a look at this issue, current implementation of
      EvictUnpinnedBuffer() IMO is erroneous - evicted buffers are lost
      permanently and will not be reused again<br>
    </p>
    <p><span style="white-space: pre-wrap">
</span></p>
    <blockquote type="cite"
      cite="mid:c4e75c92-b63f-4b45-bbcf-dddd601a9451@gmail.com"> </blockquote>
    <pre class="moz-signature" cols="72">-- 
Best regards,
Maksim Milyutin</pre>
  </body>
</html>

--------------qXiBUNN3eSAeS2dDZcafQVSJ--