https://github.com/milvus-io/milvus/issues/42589
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## Semantic Highlighting Feature
**Core Invariant**: Semantic highlighting operates on a per-field basis
with independent text processing through an external Zilliz highlight
provider. The implementation maintains field ID to field name mapping
and correlates highlight results back to original field outputs.
**What is Added**: This PR introduces semantic highlighting capability
for search results alongside the existing lexical highlighting. The
feature consists of:
- New `SemanticHighlight` orchestrator that validates queries/input
fields against collection schema, instantiates a Zilliz-based provider,
and batches text processing across multiple queries
- New `SemanticHighlighter` proxy wrapper implementing the `Highlighter`
interface for search pipeline integration
- New `semanticHighlightOperator` that processes search results by
delegating per-field text processing to the provider and attaching
correlated `HighlightResult` data to search outputs
- New gRPC service definition (`HighlightService`) and
`ZillizClient.Highlight()` method for external provider communication
**No Data Loss or Regression**: The change is purely additive without
modifying existing logic:
- Lexical highlighting path remains unchanged (separate switch case in
`createHighlightTask`)
- New `HighlightResults` field is only populated when semantic
highlighting is explicitly requested via `HighlightType_Semantic` enum
value
- Gracefully handles missing fields by returning explicit errors rather
than silent failures
- Pipeline operator integration follows existing patterns and only
processes when semantic highlighter is instantiated
**Why This Design**: Semantic highlighting is routed through the same
pipeline operator pattern as lexical highlighting, ensuring consistent
integration into search workflows. The per-field model allows flexible
highlighting across different text columns and batch processing ensures
efficient handling of multiple queries with configurable provider
constraints.
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Signed-off-by: junjie.jiang <junjie.jiang@zilliz.com>
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