Add support for Microsoft SQL Server 2016+

[DVAlexHiggs]

Hi All,

Very interested in this project, looks fantastic to me!.
I see a significant and probably quite common use case here where developers and the business will want to be reassured of a successful migration from an old legacy system to a cloud platform such as Snowflake.

As a consultant, I see a huge number of clients on MS SQL Server, and this is the source of the data for their migration from on-prem to the cloud.

I'm excited to use this tool but unfortunately it does not support most of the use cases I would want to use it for, due to the lack of MS SQL Support. To this end, I would like to suggest support for this platform.

I'm also more than happy to contribute to this, and I'm wondering if anyone can point me in the right direction for contributing please? I see the developer environment guide in the README, but what I mean is more specific information about creating a new adapter/adding new database support.

Thanks!

[nolar]

Hello. Thanks for reaching us!

MS SQL is one of the databases on the near-future roadmap. It has a few performance-related challenges though.

To make a new driver, take a look at the existing ones here: https://github.com/datafold/data-diff/tree/master/data_diff/databases — and do the same. Then also run the tests, as documented (CONTRIBUTING.md)[https://github.com/datafold/data-diff/blob/master/CONTRIBUTING.md].

If you have any questions, feel free to ask.

[DVAlexHiggs]

Hello. Thanks for reaching us!

MS SQL is one of the databases on the near-future roadmap. It has a few performance-related challenges though.

To make a new driver, take a look at the existing ones here: https://github.com/datafold/data-diff/tree/master/data_diff/databases — and do the same. Then also run the tests, as documented (CONTRIBUTING.md)[https://github.com/datafold/data-diff/blob/master/CONTRIBUTING.md].

If you have any questions, feel free to ask.

Thanks for your response!

I see there is a commented out mssql module. Anything I should know about this?

[nolar]

@DVAlexHiggs You can see more details on that in #51.

[DVAlexHiggs]

Not sure how this got closed. Think I mis-clicked

[cacondie]

@DVAlexHiggs Any update on this? I also could help contribute, but don't want to pick it up if you are already actively working on it.

[erezsh]

@cacondie ,

We are currently not pursuing this avenue, but we will be happy to accept contributions. However, be aware that the solution isn't likely to be simple.

SqlServer does support MD5 (which is what we used for hashing), but it is approx. 100 times slower than postgresql, which makes it unusable for practical purposes.

I think the solution would have to involve implementing our own checksum, probably using only simple arithmetic operations, since SQL isn't capable of much more.

Keep in mind that whatever checksum is used for SQLServer, it has to be supported by all the other databases, so that comparisons are possible. That probably means implementing this new checksum for each one. (or at least the major ones)

If you can think of a new creative solution, we'll be happy to consider it.

[icosahedron]

Would using a CLR stored procedure to compute MD5 be an option?

[masonwheeler]

Probably not as many SQL Server implementations, including just about anything on cloud storage, disallow CLR procs.

[erezsh]

I proposed a solution to this issue in #51

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