[ZEPPELIN-6411] Semantic search for Zeppelin

[kkalyan]

What is this PR for?

Added EmbeddingSearch — a new SearchService implementation that enables natural language search across Zeppelin notebooks using ONNX-based sentence embeddings (all-MiniLM-L6-v2).
Disabled by default, enabled with zeppelin.search.semantic.enable = true.

The problem:
Zeppelin's built-in search uses Lucene's keyword matching, which works well for exact terms but falls short for the way analysts actually search.
A user looking for "yesterday's spending" gets zero results — even though their notebooks contain SELECT sum(cost) WHERE date = current_date -
interval '1' day. The words don't match, so Lucene can't find it.

This PR adds EmbeddingSearch, an alternative SearchService that uses sentence embeddings (all-MiniLM-L6-v2 via ONNX Runtime) to match by meaning
instead of keywords. It runs entirely in-process with no external services required.

Beyond semantic matching, EmbeddingSearch addresses other gaps in notebook search:

• Indexes paragraph output — table results and text output become searchable, not just the code
• Extracts SQL table names — FROM/JOIN references are extracted and used to boost related paragraphs in a two-phase ranking
• Strips interpreter prefixes — %spark.sql, %python etc. are removed so they don't pollute search results
• Live indexing — new or updated paragraphs are searchable immediately, no restart needed

What type of PR is it?

Feature

Todos

• EmbeddingSearch core implementation (ONNX inference, mean pooling, cosine similarity)
• Table name extraction from SQL (FROM/JOIN regex) with two-phase search boosting
• Paragraph output indexing (TABLE, TEXT results)
• Versioned binary persistence (v3 format)
• Live indexing (new paragraphs searchable immediately)
• Angular UI: render search results with separate code/output/tables blocks
• Classic UI: same improvements
• 11 unit tests including semantic validation
• Documentation

What is the Jira issue?

• https://issues.apache.org/jira/browse/ZEPPELIN-6411

How should this be tested?

Automated tests:

# Embedding search tests (requires ~86MB model download, one-time)
ZEPPELIN_EMBEDDING_TEST=true mvn test -pl zeppelin-zengine -Dtest=EmbeddingSearchTest

# Verify no regressions to existing Lucene search
mvn test -pl zeppelin-zengine -Dtest=LuceneSearchTest

Manual testing:

1. Set zeppelin.search.semantic.enable = true in zeppelin-site.xml
2. Restart Zeppelin
3. Search for natural language queries like:
  - "yesterday's spending" (Lucene: 0 results → Semantic: finds spend queries)
  - "how much do drivers earn" (finds taxi tip analysis)
  - "late deliveries" (finds shipping performance queries)
  - "airport rides" (both work — keyword match exists)

Screenshots (if appropriate)

Semantic Search with New UI

Semantic Search with Classic UI

Questions:

• Does the license files need to update?
• Yes — NOTICE updated with ONNX Runtime (MIT) and DJL Tokenizers (Apache 2.0) attribution.
• Is there breaking changes for older versions?
• No. Disabled by default. Existing LuceneSearch behavior is unchanged.

[Copilot]

Pull request overview

This PR introduces an optional semantic notebook search implementation (EmbeddingSearch) that uses ONNX-based sentence embeddings to match queries by meaning (plus output indexing and SQL table boosting), and updates both Classic and Angular UIs to render richer search results.

Changes:

• Add EmbeddingSearch (ONNX Runtime + DJL tokenizer) with binary persistence and live indexing.
• Add semantic-search config flag (zeppelin.search.semantic.enable) and wire the server to select Lucene vs semantic search.
• Update Classic + Angular search result rendering (code/output/tables blocks) and adjust TypeScript typing/build settings.

Reviewed changes

Copilot reviewed 20 out of 20 changed files in this pull request and generated 13 comments.

Show a summary per file

File	Description
zeppelin-zengine/src/main/java/org/apache/zeppelin/search/EmbeddingSearch.java	New semantic search service (model download, embedding, indexing, persistence, query ranking).
zeppelin-zengine/src/test/java/org/apache/zeppelin/search/EmbeddingSearchTest.java	New gated tests for semantic indexing/query behavior.
zeppelin-zengine/src/main/java/org/apache/zeppelin/conf/ZeppelinConfiguration.java	Add config accessor + conf var for semantic search enablement.
zeppelin-server/src/main/java/org/apache/zeppelin/server/ZeppelinServer.java	Bind EmbeddingSearch when semantic search is enabled.
zeppelin-zengine/pom.xml	Add ONNX Runtime + DJL tokenizers dependencies.
zeppelin-web/src/app/search/result-list.html	Classic UI search results layout changes.
zeppelin-web/src/app/search/result-list.controller.js	Classic UI result parsing for code/output/tables + language badge.
zeppelin-web-angular/src/app/pages/workspace/notebook-search/result-item/result-item.component.ts	Angular UI result parsing + simplified rendering (no Monaco/highlighting).
zeppelin-web-angular/src/app/pages/workspace/notebook-search/result-item/result-item.component.html	Angular UI template to show code/output/tables and badge.
zeppelin-web-angular/src/app/pages/workspace/notebook-search/result-item/result-item.component.less	Angular UI styling for new result layout.
zeppelin-web-angular/tsconfig.base.json	TS compiler option changes.
zeppelin-web-angular/projects/zeppelin-sdk/tsconfig.json	TS compiler option changes for SDK build.
zeppelin-web-angular/src/app/utility/get-keyword-positions.ts	Tighten type for positions.
zeppelin-web-angular/src/app/share/run-scripts/run-scripts.directive.ts	Type annotations / casts for script execution logic.
zeppelin-web-angular/src/app/services/save-as.service.ts	Type annotation for binaryData.
zeppelin-web-angular/src/app/pages/workspace/notebook/paragraph/code-editor/code-editor.component.ts	Type annotation for newDecorations.
zeppelin-web-angular/src/app/pages/workspace/notebook/notebook.component.ts	Safer optional chaining on permissions access.
zeppelin-web-angular/src/app/pages/workspace/credential/credential.component.ts	Type cast for destructuring credentials.
docs/embedding-search.md	New documentation for semantic search design and usage.
NOTICE	Add attributions for ONNX Runtime and DJL tokenizers.

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[jongyoul]

@kkalyan Thank you for the contribution. Could you please check the CI first and fix it? Moreover, I will review it but I have a simple question. Do we download the model when we start the server?

[kkalyan]

@kkalyan Thank you for the contribution. Could you please check the CI first and fix it? Moreover, I will review it but I have a simple question. Do we download the model when we start the server?

Hi @jongyoul - Yes, the model (~86MB) is downloaded on first start when zeppelin.search.semantic.enable=true (disabled by default). It's cached at {zeppelin.search.index.path}/models/all-MiniLM-L6-v2/ and reused on subsequent starts. I'll fix the CI issues — ESLint brace-style in the classic UI controller and the missing ASF license header on the docs file.

[jongyoul]

I think it's better to have it by default as we need to assume the environment not to download it dynamically. Moreover, don't we need to wait until it's downloaded when starting the server?

[kkalyan]

I think it's better to have it by default as we need to assume the environment not to download it dynamically. Moreover, don't we need to wait until it's downloaded when starting the server?

Thank you @jongyoul. You're right — downloading at startup is problematic for production/air-gapped environments.
A couple of questions so I get this right:

1. Should the model be bundled in the distribution (~86MB), or would a configurable local path (zeppelin.search.model.path) where admins
   pre-stage the model be better?
2. If the model isn't found, should Zeppelin fall back to LuceneSearch with a warning, or fail fast?
3. Would an optional helper script (bin/install-search-model.sh) be acceptable for the download convenience?

Happy to implement whichever direction you prefer.