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[fix] PGVector score inversion (distance -> similarity) #3840

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[fix] PGVector score inversion (distance -> similarity) #3840

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@kubaodias kubaodias commented Dec 17, 2025

Summary

  • Convert cosine distance to similarity score (1 - distance) in PGVector search results
  • Ensures consistency with other vector stores (Qdrant, Weaviate) where higher scores indicate greater similarity
  • Fixes threshold filtering which was broken due to inverted scores (was filtering out best matches instead of worst)

Changes

  • mem0/vector_stores/pgvector.py: Add score conversion with clamping to [0, 1] range
  • tests/vector_stores/test_pgvector.py: Update 14 assertions + add TestPGVectorScoreSemantics class

Test plan

  • Run existing pgvector tests: pytest tests/vector_stores/test_pgvector.py
  • Verify score semantics tests pass (exact match → 1.0, orthogonal → 0.0)
  • Verify threshold filtering works correctly with similarity scores

Related: #3804
Precedent: #3521 (Weaviate score fix)

🤖 Generated with Claude Code
@kubaodias @claude
[fix] PGVector score inversion (distance -> similarity)
e25be1b 
Convert cosine distance to similarity score (1 - distance) to ensure
consistency with other vector stores where higher scores indicate
greater similarity.

- Update pgvector.py search method with score conversion
- Update existing test assertions to expect similarity scores
- Add TestPGVectorScoreSemantics class with semantic tests

Fixes threshold filtering which was broken due to inverted scores.

Related: mem0ai#3804

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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CLAassistant commented Dec 17, 2025 •
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@kubaodias kubaodias mentioned this pull request Dec 17, 2025
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