chore: adds validation for vector search stage's pre-filter expression MCP-242

[himanshusinghs]

Proposed changes

This PR adds an assertion to validate that if a vector search stage asks for a pre-filter using MQL expression then the fields in the MQL expression are indeed indexed as part of vector search index.

When validation is not met, we fail the tool call with MongoDBError.

Checklist

• I have signed the MongoDB CLA

[Copilot]

Pull Request Overview

This PR adds validation to ensure that fields used in $vectorSearch pre-filter MQL expressions are properly indexed in the vector search index. When validation fails, the tool call is rejected with a MongoDBError.

Key Changes:

• Adds a helper function to extract field names from vector search filter expressions
• Implements validation logic in the aggregate tool to check filter fields against the vector search index definition
• Adds comprehensive test coverage for the new validation behavior

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
tests/unit/helpers/collectFieldsFromVectorSearchFilter.test.ts	New unit tests for the filter field extraction helper
tests/integration/tools/mongodb/read/aggregate.test.ts	Integration tests validating filter field validation behavior
src/tools/mongodb/read/aggregate.ts	Implements validation logic and index field retrieval
src/helpers/collectFieldsFromVectorSearchFilter.ts	Helper to recursively extract field names from MQL filter expressions
src/common/logger.ts	Adds new log ID for validation errors

[coveralls]

Pull Request Test Coverage Report for Build 18978749862

Details

• 133 of 142 (93.66%) changed or added relevant lines in 6 files are covered.
• 24 unchanged lines in 2 files lost coverage.
• Overall coverage decreased (-0.2%) to 79.88%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/tools/mongodb/mongodbSchemas.ts	67	70	95.71%
src/tools/mongodb/read/aggregate.ts	4	10	40.0%

Files with Coverage Reduction	New Missed Lines	%
src/common/search/vectorSearchEmbeddingsManager.ts	10	82.74%
src/tools/mongodb/read/aggregate.ts	14	77.32%

Totals
Change from base Build 18977258753:	-0.2%
Covered Lines:	6479
Relevant Lines:	7989

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💛 - Coveralls

[gagik]

Changes LGTM, added a small refactor to put the assertion helper independent of the class since the tool class was getting quite huge. We might want this for others helpers we have to.