topic Re: Column [header__] change_mask in Qlik Replicate

Column [header__] change_mask

jmontoya — Fri, 15 Nov 2024 21:23:34 GMT

How to interpret [header__] change_mask column when create a replication?

How to know what does every byte means?

How to translate to varchar or another data type?

Re: Column [header__] change_mask

avidary_qlik — Mon, 18 Sep 2023 08:08:11 GMT

Please find a link to replicate's user guide re change_tables
https://help.qlik.com/en-US/replicate/May2023/Content/Replicate/Main/Change%20Tables/read_change_tables.htm#Change%20Tables:~:text=%5Bheader__%5D%20change_mask,the%20change%20mask.

In case you have any replicate version or endpoint-specific questions please open a support case.

Thank you

Avidar

Re: Column [header__] change_mask

Heinvandenheuvel — Mon, 18 Sep 2023 14:37:50 GMT

The change_mask datastructure is tricky to interpret, be sure to carefuly read and re-read the description as pointed to.

It may help to know that this structure (and the which CDC changes table) is made to mimic the SQL Server CDC mechanisme and you may want to study articles for that, to see how to possibly use the data.

For example: https://stackoverflow.com/questions/14607325/howto-interpret-the-mssql-cdc-update-mask-field and perhpas https://www.youtube.com/watch?v=4seL-ffeXtM . mind you, I didn't actually study those links, but they look like they may help.

And on you system(s) you may find: "Enumerate Net Changes Using All With Mask.sql" for example in the directory C:\Program Files (x86)\Microsoft SQL Server Management Studio 18\Common7\IDE\SqlWorkbenchProjectItems\Sql\Change Data Capture\Enumeration

fwiw,

Hein

Re: Column [header__] change_mask

Dana_Baldwin — Mon, 25 Sep 2023 21:11:19 GMT

Hi @jmontoya

If one of the replies helped to resolve the issue, please mark it as a solution & like it to make it easier for others to find.
Thanks in advance!

Re: Column [header__] change_mask

jmontoya — Mon, 02 Oct 2023 20:52:34 GMT

Thanks, It works for me. I completed with https://docs.python.org/3/library/struct.html#struct.unpack

Re: Column [header__] change_mask

yonatanyamin — Wed, 17 Sep 2025 09:05:10 GMT

Hey there,

While there are great solutions in this post, here is just another option which is to provide an example on how to unpack the bitmap using sql queries.

https://github.com/Yoniyaminhub/change_mask

please review the readme.md in the repository to understand how it works.