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From: Bagga, Rishu <[email protected]>
To: Andres Freund <[email protected]>
Cc: [email protected] <[email protected]>
Subject: Re: SLRUs in the main buffer pool - Page Header definitions
Date: Fri, 24 Jun 2022 00:39:41 +0000
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
	<[email protected]>
	<[email protected]>
	<[email protected]>

Hi Andres,


>When do we need to do so? We should never need to figure out whether an
>on-disk block is for an SLRU or something else, without also knowing >which
>relation / SLRU it is in.

You are correct that we wouldn’t need to rely on the pd_flag bit to determine page type for any access to a page where we come top down following the hierarchy. However, for the purpose of debugging “from the bottom up” it would be critical to know what type of page is being read in a system with multiple page header types.

On 6/23/22, 2:22 PM, "Andres Freund" <[email protected]> wrote:


    Hi,

    On 2022-06-23 20:25:21 +0000, Bagga, Rishu wrote:
    > >> 3. A flag to identify if the page is a relational or BufferedObject
    > >Why is this needed in the page header?
    >
    > Now that we are dealing with two different type of page headers, we need to
    > know how to interpret any given page. We need to use pd_flags to determine
    > this.

    When do we need to do so? We should never need to figure out whether an
    on-disk block is for an SLRU or something else, without also knowing which
    relation / SLRU it is in.

    Greetings,

    Andres Freund

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