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From: Laurenz Albe <[email protected]>
To: iseki zero <[email protected]>
To: [email protected]
Subject: Re: Questions about document "Concurrenry control" section
Date: Wed, 09 Oct 2024 16:51:16 +0200
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>

On Wed, 2024-10-09 at 18:07 +0800, iseki zero wrote:
> I found it difficult to understanding some paragraph in the document 
> "Concurrency control" section.
> 
>  > The Repeatable Read mode provides a rigorous guarantee that each 
> transaction sees a completely stable view of the database. However, this 
> view will not necessarily always be consistent with some serial (one at 
> a time) execution of concurrent transactions of the same level. For 
> example, even a read-only transaction at this level may see a control 
> record updated to show that a batch has been completed but/not/see one 
> of the detail records which is logically part of the batch because it 
> read an earlier revision of the control record. Attempts to enforce 
> business rules by transactions running at this isolation level are not 
> likely to work correctly without careful use of explicit locks to block 
> conflicting transactions.
> 
> At: 
> https://www.postgresql.org/docs/17/transaction-iso.html#XACT-REPEATABLE-READ:~:text=The%20Repeatable....
> 
> Specifically, I can't understand the example.

I think this is referring to this example:
https://wiki.postgresql.org/wiki/SSI#Deposit_Report

Yours,
Laurenz Albe

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