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microsoft / Analysis-Services

Git repo for Analysis Services samples and community projects
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TMDL spurious diffs #308

Open ttroutwine opened 3 weeks ago

ttroutwine commented 3 weeks ago

This version of ALM Toolkit reports differences due to mis alignment of Source to Target comparison. For columns, it will show a difference but in reality its just in a different location within the BIM. It will be the same for partitions, showing a difference but in reality its comparing 2 different partitions instead of comparing itself to the same partition.

For the partitions, this started for me after install 5.1.3 and then adding additional partitions & renaming some existing partitions.

I have deployed the source to the target, and the differences are still reported. Additionally, I used TE3 to deploy BIM files from source to target. I re ran ALM toolkit and it still reports a difference. I am not sure why it would show a difference when the BIM files are identical.

ttroutwine commented 3 weeks ago

A peer with ALM version 5.0.41 found no differences between source and target as expected. We confirmed we are using the same options when comparing

christianwade commented 3 weeks ago

Hi and thanks for reporting.

This is a known issue - internally referred to as "spurious diffs". It is an issue with TMDL serialization and affects more than just ALM Toolkit. It is documented as a known issue at the bottom of the ALM Toolkit doc. https://github.com/microsoft/Analysis-Services/blob/master/AlmToolkit/Semantic%20Model%20Comparison%20and%20Merging%20with%20ALM%20Toolkit.pdf

We have a design to fix it, and the AS team is committed to doing it, but we don't have a timeline yet. In the meantime, if this is a big enough issue, you can switch back to TMSL based diffs by changing the Options setting as described in the doc - and that should result in equivalent diffs to the previous version.

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(Another issue that reported this is here for reference: https://github.com/microsoft/Analysis-Services/issues/297#issuecomment-2357011260)