feat(insights): Update backend performance score function to handle missing vitals

[edwardgou-sentry]

Currently, if a webvital is missing, we treat the individual score as 0. This can be misleading because it negatively affects the overall performance score of an organization/project.

Instead, we want to remove any missing vital factors from the overall performance score calculation, which is what this change aims to do by updating the performance_score function.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #82750      +/-   ##
==========================================
+ Coverage   87.46%   87.66%   +0.20%     
==========================================
  Files        9407     9410       +3     
  Lines      536317   545069    +8752     
  Branches    21044    20977      -67     
==========================================
+ Hits       469088   477835    +8747     
- Misses      66859    66863       +4     
- Partials      370      371       +1     

[edwardgou-sentry]

We divide by the maximum possible weight (which will be some value between 0 - 1.0 depending on which vitals are present). This will scale up the result if there are any vitals missing.

[bcoe]

Both a 0 or a null value represent a missing vital score?

This makes sense to me, because you can't ever have an instantaneous load time for any vital metric.

[edwardgou-sentry]

The isZeroOrNull condition is ran on the count of the metric so we're really just checking for the existence of the vital, not the actual value. This is false if an lcp with value of 0ms is reported, because the count is > 0 in this case.

You're also right, it shouldn't really be possible for load time vitals to be 0ms. It might be possible for cls to be 0 though, and that would depend on if the sdk reports it.

Not sure if there's an easier clickhouse or snuba function to do this check, but this works. We'll see if there are any suggestions

[bcoe]

Refs: #77071

[gggritso]

The code makes sense! Could you add a small explanation to the function, though? The main thing that confused me is that there are weight columns in the actual metric buckets rows in ClickHouse and now there are weights when calculating the score. What's the difference between the weights?

[edwardgou-sentry]

The code makes sense! Could you add a small explanation to the function, though? The main thing that confused me is that there are weight columns in the actual metric buckets rows in ClickHouse and now there are weights when calculating the score. What's the difference between the weights?

Added an explanation!