[WIP] Support extract_snippets function in ES|QL

server/src/main/java/org/elasticsearch/search/SearchHit.java

@@ -123,7 +123,7 @@ public SearchHit(int nestedTopDocId, String id, NestedIdentity nestedIdentity) {
         this(nestedTopDocId, id, nestedIdentity, null);
     }
 
-    private SearchHit(int nestedTopDocId, String id, NestedIdentity nestedIdentity, @Nullable RefCounted refCounted) {
+    public SearchHit(int nestedTopDocId, String id, NestedIdentity nestedIdentity, @Nullable RefCounted refCounted) {
         this(
             nestedTopDocId,
             DEFAULT_SCORE,

server/src/main/java/org/elasticsearch/search/SearchModule.java

@@ -279,6 +279,8 @@
  * Sets up things that can be done at search time like queries, aggregations, and suggesters.
  */
 public class SearchModule {
+    private static volatile Map<String, Highlighter> staticHighlighters = Map.of();
+
     public static final Setting<Integer> INDICES_MAX_CLAUSE_COUNT_SETTING = Setting.intSetting(
         "indices.query.bool.max_clause_count",
         4096,
@@ -921,6 +923,10 @@ private static Map<String, Highlighter> setupHighlighters(Settings settings, Lis
         return unmodifiableMap(highlighters.getRegistry());
     }
 
+    public static Map<String, Highlighter> getStaticHighlighters() {
+        return staticHighlighters;
+    }
+
     private void registerScoreFunctions(List<SearchPlugin> plugins) {
         // ScriptScoreFunctionBuilder has it own named writable because of a new script_score query
         namedWriteables.add(
@@ -1060,6 +1066,9 @@ private void registerFetchSubPhases(List<SearchPlugin> plugins) {
         registerFetchSubPhase(new HighlightPhase(highlighters));
         registerFetchSubPhase(new FetchScorePhase());
 
+        // Store highlighters in a static map for other plugins to access
+        staticHighlighters = Map.copyOf(highlighters);
+
         FetchPhaseConstructionContext context = new FetchPhaseConstructionContext(highlighters);
         registerFromPlugin(plugins, p -> p.getFetchSubPhases(context), this::registerFetchSubPhase);
     }

server/src/main/java/org/elasticsearch/search/fetch/subphase/highlight/DefaultHighlighter.java

@@ -114,7 +114,7 @@ public HighlightField highlight(FieldHighlightContext fieldContext) throws IOExc
 
     CustomUnifiedHighlighter buildHighlighter(FieldHighlightContext fieldContext) {
         IndexSettings indexSettings = fieldContext.context.getSearchExecutionContext().getIndexSettings();
-        Encoder encoder = fieldContext.field.fieldOptions().encoder().equals("html")
+        Encoder encoder = "html".equals(fieldContext.field.fieldOptions().encoder())
             ? HighlightUtils.Encoders.HTML
             : HighlightUtils.Encoders.DEFAULT;
 

server/src/main/java/org/elasticsearch/search/fetch/subphase/highlight/HighlightSnippetUtils.java

@@ -0,0 +1,60 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the "Elastic License
+ * 2.0", the "GNU Affero General Public License v3.0 only", and the "Server Side
+ * Public License v 1"; you may not use this file except in compliance with, at
+ * your election, the "Elastic License 2.0", the "GNU Affero General Public
+ * License v3.0 only", or the "Server Side Public License, v 1".
+ */
+
+package org.elasticsearch.search.fetch.subphase.highlight;
+
+import org.apache.lucene.search.Query;
+import org.elasticsearch.index.query.QueryBuilder;
+import org.elasticsearch.index.query.SearchExecutionContext;
+
+import java.io.IOException;
+import java.util.List;
+
+/**
+ * Utility class for building highlighting queries for the purpose of extracting snippets.
+ */
+public class HighlightSnippetUtils {
+
+    public static SearchHighlightContext buildSearchHighlightContextForSnippets(
+        SearchExecutionContext searchExecutionContext,
+        String field,
+        int numSnippets,
+        int snippetCharLength,
+        QueryBuilder queryBuilder
+    ) throws IOException {
+        SearchHighlightContext.Field highlightField = buildFieldHighlightContextForSnippets(
+            searchExecutionContext,
+            field,
+            numSnippets,
+            snippetCharLength,
+            queryBuilder.toQuery(searchExecutionContext)
+        );
+        return new SearchHighlightContext(List.of(highlightField));
+    }
+
+    public static SearchHighlightContext.Field buildFieldHighlightContextForSnippets(
+        SearchExecutionContext searchExecutionContext,
+        String fieldName,
+        int numSnippets,
+        int snippetCharLength,
+        Query query
+    ) {
+        SearchHighlightContext.FieldOptions.Builder optionsBuilder = new SearchHighlightContext.FieldOptions.Builder();
+        optionsBuilder.numberOfFragments(numSnippets);
+        optionsBuilder.fragmentCharSize(snippetCharLength);
+        optionsBuilder.noMatchSize(snippetCharLength);
+        optionsBuilder.preTags(new String[] { "" });
+        optionsBuilder.postTags(new String[] { "" });
+        optionsBuilder.requireFieldMatch(false);
+        optionsBuilder.scoreOrdered(true);
+        optionsBuilder.highlightQuery(query);
+        return new SearchHighlightContext.Field(fieldName, optionsBuilder.build());
+    }
+
+}

server/src/main/java/org/elasticsearch/search/fetch/subphase/highlight/SearchHighlightContext.java

@@ -185,16 +185,16 @@ public Map<String, Object> options() {
             return options;
         }
 
-        static class Builder {
+        public static class Builder {
 
             private final FieldOptions fieldOptions = new FieldOptions();
 
-            Builder fragmentCharSize(int fragmentCharSize) {
+            public Builder fragmentCharSize(int fragmentCharSize) {
                 fieldOptions.fragmentCharSize = fragmentCharSize;
                 return this;
             }
 
-            Builder numberOfFragments(int numberOfFragments) {
+            public Builder numberOfFragments(int numberOfFragments) {
                 fieldOptions.numberOfFragments = numberOfFragments;
                 return this;
             }
@@ -209,17 +209,17 @@ Builder encoder(String encoder) {
                 return this;
             }
 
-            Builder preTags(String[] preTags) {
+            public Builder preTags(String[] preTags) {
                 fieldOptions.preTags = preTags;
                 return this;
             }
 
-            Builder postTags(String[] postTags) {
+            public Builder postTags(String[] postTags) {
                 fieldOptions.postTags = postTags;
                 return this;
             }
 
-            Builder scoreOrdered(boolean scoreOrdered) {
+            public Builder scoreOrdered(boolean scoreOrdered) {
                 fieldOptions.scoreOrdered = scoreOrdered;
                 return this;
             }
@@ -229,7 +229,7 @@ Builder highlightFilter(boolean highlightFilter) {
                 return this;
             }
 
-            Builder requireFieldMatch(boolean requireFieldMatch) {
+            public Builder requireFieldMatch(boolean requireFieldMatch) {
                 fieldOptions.requireFieldMatch = requireFieldMatch;
                 return this;
             }
@@ -269,7 +269,7 @@ Builder boundaryScannerLocale(Locale boundaryScannerLocale) {
                 return this;
             }
 
-            Builder highlightQuery(Query highlightQuery) {
+            public Builder highlightQuery(Query highlightQuery) {
                 fieldOptions.highlightQuery = highlightQuery;
                 return this;
             }
@@ -294,7 +294,7 @@ Builder options(Map<String, Object> options) {
                 return this;
             }
 
-            FieldOptions build() {
+            public FieldOptions build() {
                 return fieldOptions;
             }
 

server/src/main/java/org/elasticsearch/search/internal/SearchContext.java

@@ -28,6 +28,7 @@
 import org.elasticsearch.index.shard.IndexShard;
 import org.elasticsearch.search.RescoreDocIds;
 import org.elasticsearch.search.SearchExtBuilder;
+import org.elasticsearch.search.SearchModule;
 import org.elasticsearch.search.SearchShardTarget;
 import org.elasticsearch.search.aggregations.SearchContextAggregations;
 import org.elasticsearch.search.collapse.CollapseContext;
@@ -40,6 +41,7 @@
 import org.elasticsearch.search.fetch.subphase.FetchSourceContext;
 import org.elasticsearch.search.fetch.subphase.InnerHitsContext;
 import org.elasticsearch.search.fetch.subphase.ScriptFieldsContext;
+import org.elasticsearch.search.fetch.subphase.highlight.Highlighter;
 import org.elasticsearch.search.fetch.subphase.highlight.SearchHighlightContext;
 import org.elasticsearch.search.lookup.SourceFilter;
 import org.elasticsearch.search.profile.Profilers;
@@ -152,6 +154,10 @@ public final boolean isClosed() {
 
     public abstract void highlight(SearchHighlightContext highlight);
 
+    public Map<String, Highlighter> highlighters() {
+        return SearchModule.getStaticHighlighters();
+    }
+
     public InnerHitsContext innerHits() {
         if (innerHitsContext == null) {
             innerHitsContext = new InnerHitsContext();

x-pack/plugin/esql/compute/src/main/java/module-info.java

@@ -21,6 +21,7 @@
     requires org.elasticsearch.geo;
     requires org.elasticsearch.xcore;
     requires hppc;
+    requires org.apache.lucene.highlighter;
 
     exports org.elasticsearch.compute;
     exports org.elasticsearch.compute.aggregation;