The first commit has only a reproducer, not the fix itself.

I'm working on the latter.

Long story short, when resizing multidicts, if an object has deleted items, it may drop live items instead of collecting the deleted slots.

The fix helps with this situation.

CodSpeed Performance Report

Merging #1196 will degrade performances by 22.27%

_{Comparing asvetlov:issue-1195 (261a785) with master (c90fade)}

Summary

❌ 3 regressions
✅ 241 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.31%. Comparing base (c90fade) to head (261a785).
⚠️ Report is 40 commits behind head on master.

@@           Coverage Diff           @@
##           master    #1196   +/-   ##
=======================================
  Coverage   98.31%   98.31%           
=======================================
  Files          27       27           
  Lines        3856     3868   +12     
  Branches      704      704           
=======================================
+ Hits         3791     3803   +12     
  Misses         18       18           
  Partials       47       47           

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