batch inference should return same shape as individual inference

[generall]

Production version simply zeroed out batch alignment.
New version actually selects the proper shape

[coderabbitai]

📝 Walkthrough

Walkthrough

The _post_process_onnx_output method in fastembed/late_interaction/colbert.py was refactored to yield embeddings one at a time instead of returning entire arrays. The logic for handling document and non-document cases was updated to process and yield each embedding individually, changing the method's control flow and output format. Corresponding tests in tests/test_late_interaction_embeddings.py were updated to accommodate this change, including the addition of a new test for batch inference consistency and modifications to existing tests to compare embeddings on an element-wise basis.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~15–20 minutes

Possibly related PRs

• new: preserve embeddings in a type set by their model #492: Also modifies the _post_process_onnx_output method in fastembed/late_interaction/colbert.py, but focuses on removing explicit type conversions while retaining array returns, whereas this PR changes the method to yield embeddings.

Suggested reviewers

• joein

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📒 Files selected for processing (2)

• fastembed/late_interaction/colbert.py (2 hunks)
• tests/test_late_interaction_embeddings.py (2 hunks)

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🔇 Additional comments (4)

fastembed/late_interaction/colbert.py (2)

48-50: LGTM: Clean implementation of generator pattern for non-document case.

The change from returning arrays to yielding individual embeddings is implemented correctly for the non-document case. This aligns with the PR objective of ensuring consistent output shapes.

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67-68: LGTM: Proper filtering and yielding for document embeddings.

The implementation correctly yields filtered embeddings based on the attention mask, maintaining the same logic as before but now producing individual embeddings instead of batched arrays. This ensures consistent output shapes between batch and individual inference.

tests/test_late_interaction_embeddings.py (2)

173-188: Excellent test coverage for the PR objective.

The new test effectively validates that batch inference produces the same embedding vector lengths as individual inference, directly addressing the PR's core requirement. The test compares batch_size=1 vs batch_size=2 and verifies consistent embedding lengths.

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244-248: Proper adaptation to generator-based embeddings.

The test correctly adapts to the new generator-based output by comparing embeddings element-wise using np.allclose with appropriate tolerance (1e-3). This ensures that parallel processing still produces consistent results with the new implementation.

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[joein]

we probably also need to add it to colpali, I can do it