fix: histogram clickhouse calculation

[StarpTech]

Summary by CodeRabbit

Release Notes

• Bug Fixes
  • Fixed histogram quantile interpolation calculation to improve accuracy of metric computations.

Checklist

• I have discussed my proposed changes in an issue and have received approval to proceed.
• I have followed the coding standards of the project.
• Tests or benchmarks have been added or updated.
• Documentation has been updated on https://github.com/wundergraph/cosmo-docs.
• I have read the Contributors Guide.

[coderabbitai]

Walkthrough

Two ClickHouse migrations address a bug in the func_histogram_v2 function used for Prometheus bucket_quantile interpolation. The first migration drops the existing buggy function; the second recreates it with corrected interpolation logic using the proper Prometheus formula.

Changes

Cohort / File(s)	Summary
ClickHouse Migrations controlplane/clickhouse/migrations/20260227100333_drop_func_histogram_v2.sql, controlplane/clickhouse/migrations/20260227100342_recreate_func_histogram_v2_fix_interpolation.sql	Drop and recreate func_histogram_v2 function with corrected Prometheus bucket_quantile interpolation. The function previously used an incorrect interpolation fraction (rank / cumSum[b]); the fix implements the proper formula: lowerBound + (upperBound - lowerBound) * (rank - cumSum[b-1]) / (cumSum[b] - cumSum[b-1]) for the main interpolation case, with separate handling for boundary conditions.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Title check	✅ Passed	The title 'fix: fix histogram clickhouse calculation' clearly describes a bugfix for histogram calculations in ClickHouse, which directly relates to the PR's main objective of fixing interpolation logic in the func_histogram_v2 function.

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✨ Finishing Touches

• 📝 Generate docstrings (stacked PR)
• 📝 Generate docstrings (commit on current branch)

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 63.59%. Comparing base (1393f43) to head (7bc0eb2).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2567   +/-   ##
=======================================
  Coverage   63.59%   63.59%           
=======================================
  Files         298      298           
  Lines       41920    41920           
  Branches     4439     4439           
=======================================
  Hits        26657    26657           
  Misses      15241    15241           
  Partials       22       22           

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[wilsonrivera]

LGTM