Added docstrings, added verifySearchable to check if the field can be…

… searched, fixed issues with min_chars

src/main/java/com/yelp/nrtsearch/server/analysis/PrefixWrappedAnalyzer.java

@@ -20,11 +20,23 @@
 import org.apache.lucene.analysis.TokenFilter;
 import org.apache.lucene.analysis.ngram.EdgeNGramTokenFilter;
 
+/**
+ * An {@link AnalyzerWrapper} that wraps another analyzer and applies an Edge N-Gram token filter to
+ * the token stream.
+ */
 public class PrefixWrappedAnalyzer extends AnalyzerWrapper {
   private final int minChars;
   private final int maxChars;
   private final Analyzer delegate;
 
+  /**
+   * Create a new {@link PrefixWrappedAnalyzer} that wraps the given {@link Analyzer} and sets
+   * applies an Edge N-Gram token filter to the token stream.
+   *
+   * @param delegate the analyzer to wrap
+   * @param minChars the minimum number of characters for the edge n-grams
+   * @param maxChars the maximum number of characters for the edge n-grams
+   */
   public PrefixWrappedAnalyzer(Analyzer delegate, int minChars, int maxChars) {
     super(delegate.getReuseStrategy());
     this.delegate = delegate;
@@ -44,4 +56,9 @@ protected TokenStreamComponents wrapComponents(
         new EdgeNGramTokenFilter(components.getTokenStream(), minChars, maxChars, false);
     return new TokenStreamComponents(components.getSource(), filter);
   }
+
+  @Override
+  public String toString() {
+    return "PrefixWrappedAnalyzer(" + delegate.toString() + ")";
+  }
 }

src/main/java/com/yelp/nrtsearch/server/field/AtomFieldDef.java

@@ -153,6 +153,7 @@ public Query getRangeQuery(RangeQuery rangeQuery) {
 
   @Override
   public Query getPrefixQuery(PrefixQuery prefixQuery, MultiTermQuery.RewriteMethod rewriteMethod) {
+    verifySearchable("Prefix query");
     return new org.apache.lucene.search.PrefixQuery(
         new Term(prefixQuery.getField(), prefixQuery.getPrefix()), rewriteMethod);
   }

src/main/java/com/yelp/nrtsearch/server/field/TextFieldDef.java

@@ -42,10 +42,7 @@ public TextFieldDef(
       String name, Field requestField, FieldDefCreator.FieldDefCreatorContext context) {
     super(name, requestField, context);
     if (requestField.hasIndexPrefixes()) {
-      if (!requestField.getSearch()) {
-        throw new IllegalArgumentException(
-            "Cannot set index_prefixes on unindexed field [" + name + "]");
-      }
+      verifySearchable("Prefix query");
       int minChars =
           requestField.getIndexPrefixes().hasMinChars()
               ? requestField.getIndexPrefixes().getMinChars()
@@ -61,6 +58,8 @@ public TextFieldDef(
               getName(),
               Field.newBuilder()
                   .setSearch(true)
+                  .setAnalyzer(requestField.getAnalyzer())
+                  .setIndexAnalyzer(requestField.getIndexAnalyzer())
                   .setIndexPrefixes(
                       IndexPrefixes.newBuilder()
                           .setMinChars(minChars)
@@ -129,7 +128,8 @@ public void parseDocumentField(
 
   @Override
   public Query getPrefixQuery(PrefixQuery prefixQuery, MultiTermQuery.RewriteMethod rewriteMethod) {
-    if (prefixFieldDef != null && prefixFieldDef.accept(prefixQuery.getPrefix().length())) {
+    verifySearchable("Prefix query");
+    if (hasPrefix() && prefixFieldDef.accept(prefixQuery.getPrefix().length())) {
       Query query = prefixFieldDef.getPrefixQuery(prefixQuery);
       if (rewriteMethod == null
           || rewriteMethod == MultiTermQuery.CONSTANT_SCORE_REWRITE
@@ -147,7 +147,7 @@ public void validatePrefix(int minChars, int maxChars) {
       throw new IllegalArgumentException(
           "min_chars [" + minChars + "] must be less than max_chars [" + maxChars + "]");
     }
-    if (minChars < 2) {
+    if (minChars < 1) {
       throw new IllegalArgumentException("min_chars [" + minChars + "] must be greater than zero");
     }
     if (maxChars >= 20) {

src/main/java/com/yelp/nrtsearch/server/field/properties/PrefixQueryable.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2020 Yelp Inc.
+ * Copyright 2025 Yelp Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -15,10 +15,19 @@
  */
 package com.yelp.nrtsearch.server.field.properties;
 
+import com.yelp.nrtsearch.server.field.FieldDef;
 import com.yelp.nrtsearch.server.grpc.PrefixQuery;
 import org.apache.lucene.search.MultiTermQuery;
 import org.apache.lucene.search.Query;
 
+/** Trait interface for {@link FieldDef} types that can be queried by prefix queries. */
 public interface PrefixQueryable {
+  /**
+   * Build a prefix query for this field type with the given configuration.
+   *
+   * @param prefixQuery prefix query configuration
+   * @param rewriteMethod method to use for rewriting the prefix query
+   * @return lucene prefix query
+   */
   Query getPrefixQuery(PrefixQuery prefixQuery, MultiTermQuery.RewriteMethod rewriteMethod);
 }

src/main/java/com/yelp/nrtsearch/server/query/QueryNodeMapper.java

@@ -20,7 +20,6 @@
 import com.yelp.nrtsearch.server.analysis.AnalyzerCreator;
 import com.yelp.nrtsearch.server.doc.DocLookup;
 import com.yelp.nrtsearch.server.field.FieldDef;
-import com.yelp.nrtsearch.server.field.IndexableFieldDef;
 import com.yelp.nrtsearch.server.field.TextBaseFieldDef;
 import com.yelp.nrtsearch.server.field.properties.*;
 import com.yelp.nrtsearch.server.grpc.ExistsQuery;
@@ -51,7 +50,6 @@
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.stream.Collectors;
 import org.apache.lucene.analysis.Analyzer;
-import org.apache.lucene.index.IndexOptions;
 import org.apache.lucene.index.Term;
 import org.apache.lucene.queries.function.FunctionMatchQuery;
 import org.apache.lucene.queries.function.FunctionScoreQuery;
@@ -567,23 +565,15 @@ private Query getExistsQuery(ExistsQuery existsQuery, IndexState state) {
 
   private static Query getPrefixQuery(PrefixQuery prefixQuery, IndexState state) {
     FieldDef fieldDef = state.getFieldOrThrow(prefixQuery.getField());
-    if (!(fieldDef instanceof IndexableFieldDef)) {
-      throw new IllegalArgumentException(
-          "Field \"" + prefixQuery.getPrefix() + "\" is not indexable");
-    }
-    IndexOptions indexOptions = ((IndexableFieldDef<?>) fieldDef).getFieldType().indexOptions();
-    if (indexOptions == IndexOptions.NONE) {
-      throw new IllegalArgumentException(
-          "Field \"" + prefixQuery.getField() + "\" is not indexed with terms");
-    }
-    MultiTermQuery.RewriteMethod rewriteMethod =
-        getRewriteMethod(prefixQuery.getRewrite(), prefixQuery.getRewriteTopTermsSize());
 
     if (!(fieldDef instanceof PrefixQueryable)) {
       throw new IllegalArgumentException(
-          "Field " + fieldDef.getName() + "does not support PrefixQuery");
+          "Field " + fieldDef.getName() + " does not support PrefixQuery");
     }
 
+    MultiTermQuery.RewriteMethod rewriteMethod =
+        getRewriteMethod(prefixQuery.getRewrite(), prefixQuery.getRewriteTopTermsSize());
+
     return ((PrefixQueryable) fieldDef).getPrefixQuery(prefixQuery, rewriteMethod);
   }
 

src/test/java/com/yelp/nrtsearch/server/field/PrefixFieldDefTest.java

@@ -70,12 +70,12 @@ public void testInvalidMinChars() {
       Field field =
           Field.newBuilder()
               .setSearch(true)
-              .setIndexPrefixes(IndexPrefixes.newBuilder().setMinChars(1).setMaxChars(5).build())
+              .setIndexPrefixes(IndexPrefixes.newBuilder().setMinChars(0).setMaxChars(5).build())
               .build();
       createFieldDef(field);
-      fail("Should throw IllegalArgumentException for min_chars < 2");
+      fail("Should throw IllegalArgumentException for min_chars < 1");
     } catch (IllegalArgumentException e) {
-      assertEquals("min_chars [1] must be greater than zero", e.getMessage());
+      assertEquals("min_chars [0] must be greater than zero", e.getMessage());
     }
   }
 

src/test/java/com/yelp/nrtsearch/server/query/PrefixQueryTest.java

@@ -122,7 +122,7 @@ public void testFieldNotIndexable() {
       doQuery("virtual", "prefix");
       fail();
     } catch (StatusRuntimeException e) {
-      assertTrue(e.getMessage().contains("Field \"prefix\" is not indexable"));
+      assertTrue(e.getMessage().contains("Field virtual does not support PrefixQuery"));
     }
   }
 
@@ -133,7 +133,8 @@ public void testFieldNoTerms() {
       fail();
     } catch (StatusRuntimeException e) {
       assertTrue(
-          e.getMessage().contains("Field \"text_field.not_searchable\" is not indexed with terms"));
+          e.getMessage()
+              .contains("Prefix query requires field to be searchable: text_field.not_searchable"));
     }
   }