(feat) #2198 add postgres backend similarity functions to fully supported

[vfrank66]

…rt comparisons

Type of PR

• [ ] BUG
• [X ] FEAT
• [ ] MAINT
• [ ] DOC

Is your Pull Request linked to an existing Issue or Pull Request?

2198 add similarity functions to postgres backend to enable comparison_level_library

Give a brief description for the solution you have provided

There are two options creating using the existing pg_similarity extension, or codifing the specific functions. I added the specific functions to implement comparison level library for postgres.

PR Checklist

• [ ] Added documentation for changes
• [ ] Added feature to example notebooks or tutorial (if appropriate)
• [ ] Added tests (if appropriate)
• [ ] Updated CHANGELOG.md (if appropriate)
• [ ] Made changes based off the latest version of Splink
• [ ] Run the linter
• [ ] Run the spellchecker (if appropriate)

I could not find the developer docs 404 not found so i did not add tests or docs, but I did run the linter. UPDATE: nevermind I guess I did not run the formatting. The lint_and_format.sh is not up-to-date with ruff do you want this updated as well. It is very confusing I am getting more ruff errors locally than I changed something is off.

[RobinL]

Hi @vfrank66 thanks very much for this. We're a bit short staffed at the moment but will endeavour to review ASAP. Don't worry too much about the test failures for now

[RobinL]

Hi @vfrank66 i've started to have a look at this, and do some experiments. All working so far.

Could I double check - are the implementations of the new similarity functions in splink/postgres/linker.py your own? i.e. we don't need to include any licence with them?

To make it easier to get the tests passing, I'll probably create a new PR of your commits on the main repo, so I can start to add commits on top until I'm happy with all the tests. Then I can check with you before merging.

[RobinL]

Closing in favour of #2224