[goutamadwant]

Fixes #26492

Long MongoDB string IDs can overflow when LexicographicKeyRangeTracker converts the integer delta to float before division.

This uses Python 3 true division directly and adds regression coverage for long bytes and str keys.

Before: 400-character keys raise OverflowError: int too large to convert to float.

After: the same keys return the expected fraction (0.48).

Tests:

• python -m unittest -q apache_beam.io.range_trackers_test — 28 passed
• python -m unittest -q apache_beam.io.mongodbio_test — 131 passed

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 56.15%. Comparing base (b4db8d2) to head (cd7c2ec).

Additional details and impacted files

@@             Coverage Diff              @@
##             master   #40330      +/-   ##
============================================
- Coverage     56.16%   56.15%   -0.01%     
  Complexity     2290     2290              
============================================
  Files          1121     1121              
  Lines        177158   177158              
  Branches       1486     1486              
============================================
- Hits          99494    99481      -13     
- Misses        75143    75156      +13     
  Partials       2521     2521              

Flag	Coverage Δ
python	79.84% <100.00%> (-0.02%)	⬇️

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[github-actions]

Assigning reviewers:

R: @jrmccluskey for label python.

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[goutamadwant]

retest this please

[jrmccluskey]

LGTM, thanks! Will merge after the precommit re-run finishes