Support $eq comparision operator

[ribaraka]

Refs #251.

[CLAassistant]

All committers have signed the CLA.

[AlekSi]

Please sign the CLA, merge with main, fix CI issues

[codecov]

Codecov Report

Merging #309 (67d8bbf) into main (8186b0a) will increase coverage by 0.25%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #309      +/-   ##
==========================================
+ Coverage   57.39%   57.65%   +0.25%     
==========================================
  Files         117      117              
  Lines        6014     6031      +17     
==========================================
+ Hits         3452     3477      +25     
+ Misses       2047     2039       -8     
  Partials      515      515              

Flag	Coverage Δ
FerretDB	32.25% <18.51%> (-0.09%)	⬇️
MongoDB	2.70% <0.00%> (-0.01%)	⬇️
integration	32.29% <18.51%> (-0.09%)	⬇️
tests	51.19% <100.00%> (+0.27%)	⬆️

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Impacted Files	Coverage Δ
internal/handlers/common/compare.go	84.30% <100.00%> (+1.56%)	⬆️
internal/handlers/common/filter.go	84.90% <100.00%> (+1.62%)	⬆️
internal/util/testutil/equal.go	48.79% <0.00%> (+1.80%)	⬆️

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[AlekSi]

Where is a PR to https://github.com/FerretDB/dance?

[AlekSi]

Some of our dance tests fail with MongoDB, meaning that FerretDB and MongoDB behave differently. That's a problem that should be fixed.

[ribaraka]

I removed the TODO regex from the $eq comparison operator. I have not find any information in the documentation and on the Internet that these two expressions were used.
I also tried to issue query in mongosh db.values.find( { value: {$eq :/foo/i } } ) to the values database manually and it returns only match stored regexes. I mean is there possibility who would store regex datatype in a document? Anyway current implementation FerretDB returns nothing.
What do you think we will do next?

[AlekSi]

I mean is there possibility who would store regex datatype in a document?

Yes.

Anyway current implementation FerretDB returns nothing.

We should add a dance test for that case and fix that difference in behavior between MongoDB and FerretDB.

[AlekSi]

Thank you!