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Pagetracking return null data if checkpoint LSN is less than page tracking start LSn

Description

Background
When we start page tracking,  it is started from the current system LSN A. This means all the pages that are flushed after that are tracked. 

After some time If I am interested in knowing the count of modified pages at the time I started page tracking till the current moment(current checkpoint LSN B) .  MySQL provides an interface

Select mysqlbackup_page_track_get_changed_page_count( A,B);

Where A is the LSN when the page tracking was started.  B is checkpoint LSN. If we provide B=0, B would take the current checkpoint LSN. 

Problem
MySQL has put a restriction that checkpoint LSN B > A.  For a system with a huge redo current system LSN and checkpoint LSN could be apart. 
A could be greater than B even after some time. 

If our interest in knowing all modified pages to the moment.  Why do we need this restriction? 

I tried removing the restriction. I can get changed pages successfully.  I checked the clone which also need pagetracking data and there is no restriction. 

Please see if there is a reason for this restriction or if we can remove that. 

Environment

None

Attachments

1
  • 06 Apr 2023, 05:27 AM

Activity

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Rahul Malik April 6, 2023 at 5:27 AM

This condition can be removed with attached patch.

Details

Assignee

Reporter

Labels

Upstream Bug URL

https://bugs.mysql.com/bug.php?id=110663
https://bugs.mysql.com/bug.php?id=110663

Needs QA

Yes

Affects versions

Priority

Smart Checklist

Created April 6, 2023 at 5:23 AM
Updated December 6, 2024 at 11:44 AM

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