Implement Lucene EstonianAnalyzer, Stemmer (#49149)

This PR adds a new analyzer and stemmer for the Estonian language.

Closes #48895

docs/reference/analysis/analyzers/lang-analyzer.asciidoc

@@ -15,6 +15,7 @@ following types are supported:
 <<danish-analyzer,`danish`>>,
 <<dutch-analyzer,`dutch`>>,
 <<english-analyzer,`english`>>,
+<<estonian-analyzer,`estonian`>>,
 <<finnish-analyzer,`finnish`>>,
 <<french-analyzer,`french`>>,
 <<galician-analyzer,`galician`>>,
@@ -669,6 +670,54 @@ PUT /english_example
 // TEST[s/"english_keywords",//]
 // TEST[s/\n$/\nstartyaml\n  - compare_analyzers: {index: english_example, first: english, second: rebuilt_english}\nendyaml\n/]
 
+<1> The default stopwords can be overridden with the `stopwords`
+    or `stopwords_path` parameters.
+<2> This filter should be removed unless there are words which should
+    be excluded from stemming.
+
+[[estonian-analyzer]]
+===== `estonian` analyzer
+
+The `estonian` analyzer could be reimplemented as a `custom` analyzer as follows:
+
+[source,console]
+----------------------------------------------------
+PUT /estonian_example
+{
+  "settings": {
+    "analysis": {
+      "filter": {
+        "estonian_stop": {
+          "type":       "stop",
+          "stopwords":  "_estonian_" <1>
+        },
+        "estonian_keywords": {
+          "type":       "keyword_marker",
+          "keywords":   ["näide"] <2>
+        },
+        "estonian_stemmer": {
+          "type":       "stemmer",
+          "language":   "estonian"
+        }
+      },
+      "analyzer": {
+        "rebuilt_estonian": {
+          "tokenizer":  "standard",
+          "filter": [
+            "lowercase",
+            "estonian_stop",
+            "estonian_keywords",
+            "estonian_stemmer"
+          ]
+        }
+      }
+    }
+  }
+}
+----------------------------------------------------
+// TEST[s/"estonian_keywords",//]
+// TEST[s/\n$/\nstartyaml\n  - compare_analyzers: {index: estonian_example, first: estonian, second: rebuilt_estonian}\nendyaml\n/]
+
 <1> The default stopwords can be overridden with the `stopwords`
     or `stopwords_path` parameters.
 <2> This filter should be removed unless there are words which should

docs/reference/analysis/tokenfilters/stop-tokenfilter.asciidoc

@@ -70,7 +70,7 @@ PUT /my_index
 Elasticsearch provides the following predefined list of languages:
 
 `_arabic_`, `_armenian_`, `_basque_`, `_bengali_`, `_brazilian_`, `_bulgarian_`,
-`_catalan_`, `_czech_`, `_danish_`, `_dutch_`, `_english_`, `_finnish_`,
+`_catalan_`, `_czech_`, `_danish_`, `_dutch_`, `_english_`, `_estonian_`, `_finnish_`,
 `_french_`, `_galician_`, `_german_`, `_greek_`, `_hindi_`, `_hungarian_`,
 `_indonesian_`, `_irish_`, `_italian_`, `_latvian_`, `_norwegian_`, `_persian_`,
 `_portuguese_`, `_romanian_`, `_russian_`, `_sorani_`, `_spanish_`,

modules/analysis-common/src/main/java/org/elasticsearch/analysis/common/CommonAnalysisPlugin.java

@@ -56,6 +56,7 @@ import org.apache.lucene.analysis.en.EnglishAnalyzer;
 import org.apache.lucene.analysis.en.KStemFilter;
 import org.apache.lucene.analysis.en.PorterStemFilter;
 import org.apache.lucene.analysis.es.SpanishAnalyzer;
+import org.apache.lucene.analysis.et.EstonianAnalyzer;
 import org.apache.lucene.analysis.eu.BasqueAnalyzer;
 import org.apache.lucene.analysis.fa.PersianAnalyzer;
 import org.apache.lucene.analysis.fa.PersianNormalizationFilter;
@@ -193,6 +194,7 @@ public class CommonAnalysisPlugin extends Plugin implements AnalysisPlugin, Scri
         analyzers.put("danish", DanishAnalyzerProvider::new);
         analyzers.put("dutch", DutchAnalyzerProvider::new);
         analyzers.put("english", EnglishAnalyzerProvider::new);
+        analyzers.put("estonian", EstonianAnalyzerProvider::new);
         analyzers.put("finnish", FinnishAnalyzerProvider::new);
         analyzers.put("french", FrenchAnalyzerProvider::new);
         analyzers.put("galician", GalicianAnalyzerProvider::new);
@@ -349,6 +351,7 @@ public class CommonAnalysisPlugin extends Plugin implements AnalysisPlugin, Scri
         analyzers.add(new PreBuiltAnalyzerProviderFactory("danish", CachingStrategy.LUCENE, DanishAnalyzer::new));
         analyzers.add(new PreBuiltAnalyzerProviderFactory("dutch", CachingStrategy.LUCENE, DutchAnalyzer::new));
         analyzers.add(new PreBuiltAnalyzerProviderFactory("english", CachingStrategy.LUCENE, EnglishAnalyzer::new));
+        analyzers.add(new PreBuiltAnalyzerProviderFactory("estonian", CachingStrategy.LUCENE, EstonianAnalyzer::new));
         analyzers.add(new PreBuiltAnalyzerProviderFactory("finnish", CachingStrategy.LUCENE, FinnishAnalyzer::new));
         analyzers.add(new PreBuiltAnalyzerProviderFactory("french", CachingStrategy.LUCENE, FrenchAnalyzer::new));
         analyzers.add(new PreBuiltAnalyzerProviderFactory("galician", CachingStrategy.LUCENE, GalicianAnalyzer::new));

modules/analysis-common/src/main/java/org/elasticsearch/analysis/common/EstonianAnalyzerProvider.java

@@ -0,0 +1,45 @@
+/*
+ * Licensed to Elasticsearch under one or more contributor
+ * license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright
+ * ownership. Elasticsearch licenses this file to you under
+ * the Apache License, Version 2.0 (the "License"); you may
+ * not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+
+package org.elasticsearch.analysis.common;
+
+import org.apache.lucene.analysis.CharArraySet;
+import org.apache.lucene.analysis.et.EstonianAnalyzer;
+import org.elasticsearch.common.settings.Settings;
+import org.elasticsearch.env.Environment;
+import org.elasticsearch.index.IndexSettings;
+import org.elasticsearch.index.analysis.AbstractIndexAnalyzerProvider;
+import org.elasticsearch.index.analysis.Analysis;
+
+public class EstonianAnalyzerProvider extends AbstractIndexAnalyzerProvider<EstonianAnalyzer> {
+
+    private final EstonianAnalyzer analyzer;
+
+    EstonianAnalyzerProvider(IndexSettings indexSettings, Environment env, String name, Settings settings) {
+        super(indexSettings, name, settings);
+        analyzer = new EstonianAnalyzer(
+            Analysis.parseStopWords(env, settings, EstonianAnalyzer.getDefaultStopSet()),
+            Analysis.parseStemExclusion(settings, CharArraySet.EMPTY_SET)
+        );
+        analyzer.setVersion(version);
+    }
+
+    @Override
+    public EstonianAnalyzer get() { return this.analyzer; }
+}

modules/analysis-common/src/main/java/org/elasticsearch/analysis/common/StemmerTokenFilterFactory.java

@@ -65,6 +65,7 @@ import org.tartarus.snowball.ext.CatalanStemmer;
 import org.tartarus.snowball.ext.DanishStemmer;
 import org.tartarus.snowball.ext.DutchStemmer;
 import org.tartarus.snowball.ext.EnglishStemmer;
+import org.tartarus.snowball.ext.EstonianStemmer;
 import org.tartarus.snowball.ext.FinnishStemmer;
 import org.tartarus.snowball.ext.FrenchStemmer;
 import org.tartarus.snowball.ext.German2Stemmer;
@@ -142,6 +143,9 @@ public class StemmerTokenFilterFactory extends AbstractTokenFilterFactory {
         } else if ("possessive_english".equalsIgnoreCase(language) || "possessiveEnglish".equalsIgnoreCase(language)) {
             return new EnglishPossessiveFilter(tokenStream);
 
+        } else if ("estonian".equalsIgnoreCase(language)) {
+            return new SnowballFilter(tokenStream, new EstonianStemmer());
+
             // Finnish stemmers
         } else if ("finnish".equalsIgnoreCase(language)) {
             return new SnowballFilter(tokenStream, new FinnishStemmer());

modules/analysis-common/src/test/resources/rest-api-spec/test/analysis-common/20_analyzers.yml

@@ -478,6 +478,35 @@
     - length: { tokens: 1 }
     - match:  { tokens.0.token: book }
 
+---
+"estonian":
+    - do:
+        indices.create:
+          index: test
+          body:
+            settings:
+              analysis:
+                analyzer:
+                  my_analyzer:
+                    type: estonian
+
+    - do:
+        indices.analyze:
+          body:
+            text:     teadaolevalt
+            analyzer: estonian
+    - length: { tokens: 1 }
+    - match:  { tokens.0.token: teadaole }
+
+    - do:
+        indices.analyze:
+          index: test
+          body:
+            text:     teadaolevalt
+            analyzer: my_analyzer
+    - length: { tokens: 1 }
+    - match:  { tokens.0.token: teadaole }
+
 ---
 "finnish":
     - do:

server/src/main/java/org/elasticsearch/index/analysis/Analysis.java

@@ -33,6 +33,7 @@ import org.apache.lucene.analysis.de.GermanAnalyzer;
 import org.apache.lucene.analysis.el.GreekAnalyzer;
 import org.apache.lucene.analysis.en.EnglishAnalyzer;
 import org.apache.lucene.analysis.es.SpanishAnalyzer;
+import org.apache.lucene.analysis.et.EstonianAnalyzer;
 import org.apache.lucene.analysis.eu.BasqueAnalyzer;
 import org.apache.lucene.analysis.fa.PersianAnalyzer;
 import org.apache.lucene.analysis.fi.FinnishAnalyzer;
@@ -127,6 +128,7 @@ public class Analysis {
         namedStopWords.put("_danish_", DanishAnalyzer.getDefaultStopSet());
         namedStopWords.put("_dutch_", DutchAnalyzer.getDefaultStopSet());
         namedStopWords.put("_english_", EnglishAnalyzer.getDefaultStopSet());
+        namedStopWords.put("_estonian_", EstonianAnalyzer.getDefaultStopSet());
         namedStopWords.put("_finnish_", FinnishAnalyzer.getDefaultStopSet());
         namedStopWords.put("_french_", FrenchAnalyzer.getDefaultStopSet());
         namedStopWords.put("_galician_", GalicianAnalyzer.getDefaultStopSet());