Fix #480: Multi Vector > 10000 documents throws scoring error

[JiwaniZakir]

Closes #480

When a MultiVectorQuery runs against an index with more than 10,000 documents, Redis does not yield a distance value for every document, causing the bare (2 - @distance_i)/2 expression in MultiVectorQuery.__init__ (redisvl/query/aggregate.py) to raise "Could not find the value for a parameter name". The fix wraps each apply() call in an if(exists(@distance_i), (2 - @distance_i)/2, 0) guard so that documents missing a distance score default to 0 instead of erroring.

• redisvl/query/aggregate.py — MultiVectorQuery.__init__: replaced the two bare apply() expressions with if(exists(...), ..., 0) variants.
• tests/unit/test_aggregation_types.py — test_multi_vector_query_string: updated the expected query string to match the new if(exists(...)) form.

The fix was verified by updating the unit test in test_aggregation_types.py, which asserts the full serialized aggregation string and now passes with the new expression.

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This PR was created with AI assistance (Claude). The changes were reviewed by quality gates and a critic model before submission.

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Note

Low Risk
Low risk: small query-string change that only affects how missing @distance_i values are handled, plus a matching unit-test update.

Overview
Fixes MultiVectorQuery scoring failures when Redis does not return @distance_i for some documents by wrapping each per-vector score calculation in if(exists(@distance_i), (2 - @distance_i)/2, 0) so missing distances default to 0 instead of erroring.

Updates the unit test asserting the serialized aggregation query string to match the new guarded APPLY expressions.

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[Copilot]

Pull request overview

Fixes an aggregation scoring failure in MultiVectorQuery when Redis does not yield a distance_i value for some documents (reported when querying indexes with >10,000 documents), by guarding the distance-to-similarity conversion with exists() and defaulting missing distances to a score of 0.

Changes:

• Wrap per-vector similarity computation in if(exists(@distance_i), ..., 0) to prevent APPLY from erroring when @distance_i is missing.
• Update the unit test’s expected serialized aggregation string to match the new guarded APPLY expressions.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
redisvl/query/aggregate.py	Adds an exists() guard around per-vector distance normalization to avoid aggregation errors when distance_i is absent.
tests/unit/test_aggregation_types.py	Updates the expected query string for MultiVectorQuery to reflect the new if(exists(...)) scoring expression.

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