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Type: Improvement
Resolution: Fixed
Priority: Major - P3
Fix Version/s: 8.2.0-rc0, 8.0.14
Affects Version/s: None
Component/s: None
Labels:
None

Assigned Teams:

Query Integration
Backwards Compatibility:
Minor Change
Linked BF Score:
0
CAR Domain/s:
None

Aha! Reference:
None
Tracking Level:
None
Risk Status:
None
Exec Notes:
None
Goal Name(s):
None
Goal Link:
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Estimated Weeks:
0

Currently both hybrid search stages ($rankFusion & $scoreFusion) analyze the desugared version of there input pipelines (as Pipeline object).

Here for $rankFusion
Here for $scoreFusion

This is not ideal because we have constraints for both input pipeline (that is that they must both be selection pipelines, and also be ranked/scored pipelines); but analyzing the desugared version makes it difficult to recognize these rules after some valid stages desugar into other stages (like $score).

Instead we should analyze the pre-desugared version of the input pipelines (that is the input pipeline parsed as a LiteParsedPipeline), and then later parse to a full Pipeline.

So for both $rankFusion and $scoreFusion we should:

Parse the input pipeline to LiteParsedPipeline (here / here)
Modify the input pipeline validator functions to analyze the LiteParsedPipeline
After validation passes, then parse to full Pipeline, and all downstream logic for both stages should remain unaffected (ideally we would "upgrade" from a LiteParsedPipeline to a full Pipeline, but that functionality does not currently exist).

Furthermore, we should look for all opportunities to consolidate logic between $rankFusion and $scoreFusion in the document_source_hybrid_scoring_util files. Here is my suggestion:

Have 3 util functions that all analyze a LiteParsedPipeline
- 'isSelectionPipeline': has only the stages defined here in TDD
- 'isRankedPipeline': rules defined here in TDD
- 'isScoredPipeline': rules defined here in TDD

Then the input pipeline validation functions can look like:

$rankFusion: isSelectionPipeline && isRankedPipeline
$scoreFusion: isSelectionPipeline && isScoredPipeline

Also remember to retain the generatesMetadataType(DocumentMetadataFields::kScore) check once a Pipeline is created (after LiteParsedPipeline input pipeline analysis).

This change should also set us up to support nested hybrid searches, if we later choose to support these. It might end up being trivial to support if this goes well.

Testing:

All existing tests in our hybrid search suites should continue to pass.

Add tests for placing a $score with $minMaxScaler normalization inside of $scoreFusion input pipeline. This should have already worked, but doesn't because $score with $minMaxScaler desugars into stages that don't currently pass input pipeline validation - so this change should also fix this case. Make sure to add tests with both $scoreFusion and $score requesting scoreDetails and not.

is depended on by

SERVER-104730 Explicitly ban nested $rankFusions and $scoreFusions

Closed

is related to

SERVER-104636 Do not serialize _internalOutputSortKeyMetadata in query shape hash

Closed

SERVER-97189 $rankFusion and $scoreFusion are missing parsing assertions

Closed

SERVER-107409 View definitions with stages that include $rankFusion with subpipelines are not getting disallowed

Closed

SERVER-108052 DocumentSourceInternalSetWindowFields doesn't have sort key metadata in bounded sorts

Closed

SERVER-101702 Add tests for $rankFusion in $lookup/$unionWith subpipelines

Closed

SERVER-101781 Reject $rankFusion in a view definiton

Closed

SERVER-102728 Audit rankFusion's scoreDetails testing

Closed

related to

SERVER-104636 Do not serialize _internalOutputSortKeyMetadata in query shape hash

Closed

SERVER-96764 Create geoNear index in rankFusion auth test

Closed

SERVER-97189 $rankFusion and $scoreFusion are missing parsing assertions

Closed

SERVER-98343 $rankFusion seg faults if given empty pipeline

Closed

SERVER-99887 $setWindowFields can fail when spilling to disk

Closed

SERVER-100394 Validation of score $meta field is skipped for mongot queries

Closed

SERVER-101653 Do not allow rankFusion to run on views

Closed

SERVER-105677 $skip is incorrectly disallowed inside $rankFusion

Closed

SERVER-107409 View definitions with stages that include $rankFusion with subpipelines are not getting disallowed

Closed

SERVER-108052 DocumentSourceInternalSetWindowFields doesn't have sort key metadata in bounded sorts

Closed

SERVER-94669 Implement 'scoreDetails' for $rankFusion

Closed

SERVER-94841 Implement 'score' for $score

Closed

SERVER-91200 Add end-to-end ranked fusion test using existing syntax

Closed

SERVER-91201 Add end-to-end score fusion test using existing syntax

Closed

SERVER-82019 Create feature flag

Closed

SERVER-91278 Allow sorting by more kinds of metadata

Closed

SERVER-91279 Add example rank fusion tests which use $setWindowFields

Closed

SERVER-91281 Allow $rank and $denseRank window functions to operate without a SortKeyPattern

Closed

SERVER-91907 Create skeleton of DocumentSourceRankFusion

Closed

SERVER-91909 Implement basic parsing of $rankFusion

Closed

SERVER-91911 Add validation that $rankFusion subpipelines are valid

Closed

SERVER-91912 Test auth for $rankFusion stage

Closed

SERVER-92213 Implement desugaring of $rankFusion

Closed

SERVER-92244 Create Feature Flag for Milestones 1 and 2

Closed

SERVER-92357 Create js testing strategy for search scoring differences in sharded vs non-sharded configurations

Closed

SERVER-94603 Add 'weights' argument to $rankFusion

Closed

SERVER-94660 Test $rankFusion query shape and stable API restrictions

Closed

SERVER-94668 POC 'scoreDetails' for $score

Closed

SERVER-96064 Optimize away $sort directly after $vectorSearch for single node environments

Closed

SERVER-96736 Switch $rankFusion to use 'featureFlagSearchHybridScoringPrerequisites'

Closed

SERVER-97339 Implement serialization and query shape testing for $score

Closed

SERVER-97645 Refactor serializeTransformation to remove redundant explain parameter

Closed

SERVER-97915 Create feature flag for earlier $rankFusion milestone

Closed

SERVER-97917 Move $rankFusion to be guarded under featureFlagRankFusionBasic

Closed

SERVER-97919 Enable featureFlagRankFusionBasic by default

Closed

SERVER-98453 Refactor $sort to make it easier to add a new option

Closed

SERVER-98994 Make featureFlagRankFusionBasic FCV-gated

Closed

SERVER-99153 $rankFusion scoreDetails should error if not requested by top-level pipeline (but specified in inner)

Closed

SERVER-99169 score cannot be used when not defined

Closed

SERVER-99210 $rankFusion should reject duplicate input.pipelines names

Closed

SERVER-99335 Support projecting textScore with $meta: score

Closed

SERVER-99589 Consolidate metadata dependency tracking of search and non-search metadata

Closed

SERVER-99596 Refactor how metadata dependencies are validated

Closed

SERVER-100045 Add property-based test for metadata field dependency validation

Closed

SERVER-100107 Add "description" and "weight" to $rankFusion scoreDetails

Closed

SERVER-100203 Change scoreDetails to use array rather than object

Closed

SERVER-100546 Handle deps tracking generically in DocumentSourceFacet::getDependencies()

Closed

SERVER-100678 scoreDetails cannot be used when not defined

Closed

SERVER-100799 Guard meta_dependency_validation.js on featureFlagRankFusionFull

Closed

SERVER-100948 Re-enable scoreDetails "value" field

Closed

SERVER-101155 Run search e2e metadata tests in the search passthroughs

Closed

SERVER-101701 $rankFusion must be the first stage of the pipeline

Closed

SERVER-101702 Add tests for $rankFusion in $lookup/$unionWith subpipelines

Closed

SERVER-101781 Reject $rankFusion in a view definiton

Closed

SERVER-107693 [v8.0] Backport Hybrid Search Rank Fusion

Closed

SERVER-99505 Refactor string building in document_source_rank_fusion.cpp

Closed

SERVER-101568 $rankFusion should reject scoreDetails: true unless FF is on

Closed

SERVER-88046 Support $vectorSearch execution within unionWith subpipeline

Closed

SERVER-93391 Remove rankConstant field from $rankFusion

Closed

SERVER-93576 Remove vector embeddings from $vectorSearch explain

Closed

SERVER-95162 Refactor multiversion query test to make it more re-usable

Closed

SERVER-95164 Allow more than 2 input pipelines for $rankFusion

Closed

SERVER-95168 Implement $setWindowFields version of desugaring for $rankFusion

Closed

SERVER-95169 Add multiversion query test which stresses sharded scenarios

Closed

SERVER-96127 Adjust $rankFusion syntax to adopt 'input.pipelines' revision

Closed

SERVER-96154 Validate field names for 'inputs.pipelines' and 'weights'

Closed

SERVER-96792 Allow {$meta: "score"} to return any kind of score metadata

Closed

SERVER-96793 Allow {$meta: "scoreDetails"} to return any kind of scoreDetails metadata

Closed

SERVER-97103 Allow sorting by {$meta: "score"}

Closed

SERVER-97104 Restrict {$meta: "scoreDetails"} to featureFlagRankFusionFull and apiStrict=false

Closed

SERVER-98322 Improve field path validation error messages

Closed

SERVER-99674 Change $rankFusion weights object to accept a subset of pipelines specified

Closed

SERVER-99675 Improve feedback for misspelled $rankFusion pipelines in weights object

Closed

SERVER-99732 Switch sort key metadata assertion to tassert (from invariant)

Closed

SERVER-100752 $rankFusion should output score metadata

Closed

SERVER-102728 Audit rankFusion's scoreDetails testing

Closed

SERVER-96835 Update commands_lib.js rankFusion pipeline to new syntax.

Closed

SERVER-97102 Stress test dependency tracking for {$meta: "scoreDetails"} for pipelines spanning across sharded network split

Closed

(3 is related to, 78 related to)

Assignee:: Finley Lau
Reporter:: Joe Shalabi
Participants:: Finley Lau, Githook User, Joe Shalabi
Votes:: 0 Vote for this issue
Watchers:: 2 Start watching this issue

Created:: May 21 2025 08:12:41 PM UTC
Updated:: Aug 22 2025 08:23:04 PM UTC
Resolved:: Jun 06 2025 01:40:26 PM UTC

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