Add limits for ngram and shingle settings

Create index-level settings:
max_ngram_diff - maximum allowed difference between max_gram and min_gram in
NGramTokenFilter/NGramTokenizer. Default is 1.
max_shingle_diff - maximum allowed difference betweenmax_shingle_size and
 min_shingle_size in ShingleTokenFilter.  Default is 3.

Throw an IllegalArgumentException from v7.X when
trying to create NGramTokenFilter, NGramTokenizer, ShingleTokenFilter
where difference between max_size and min_size exceeds the settings value.
Create a deprecated warning for versions < 7.X for this case.

Closes #25887

core/src/main/java/org/elasticsearch/index/analysis/NGramTokenizerFactory.java

@@ -21,6 +21,7 @@
 
 import org.apache.lucene.analysis.Tokenizer;
 import org.apache.lucene.analysis.ngram.NGramTokenizer;
+import org.elasticsearch.Version;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.env.Environment;
 import org.elasticsearch.index.IndexSettings;
@@ -89,10 +90,15 @@ public NGramTokenizerFactory(IndexSettings indexSettings, Environment environmen
         this.maxGram = settings.getAsInt("max_gram", NGramTokenizer.DEFAULT_MAX_NGRAM_SIZE);
         int ngramDiff = maxGram - minGram;
         if (ngramDiff > maxAllowedNgramDiff) {
-            throw new IllegalArgumentException(
-                "The difference between max_gram and min_gram in NGram Tokenizer must be less than or equal to: [" + maxAllowedNgramDiff
-                    + "] but was [" + ngramDiff + "]. This limit can be set by changing the ["
-                    + IndexSettings.MAX_NGRAM_DIFF_SETTING.getKey() + "] index level setting.");
+            if (indexSettings.getIndexVersionCreated().onOrAfter(Version.V_7_0_0_alpha1)) {
+                throw new IllegalArgumentException(
+                    "The difference between max_gram and min_gram in NGram Tokenizer must be less than or equal to: ["
+                        + maxAllowedNgramDiff + "] but was [" + ngramDiff + "]. This limit can be set by changing the ["
+                        + IndexSettings.MAX_NGRAM_DIFF_SETTING.getKey() + "] index level setting.");
+            } else {
+                deprecationLogger.deprecated("Deprecated big difference between max_gram and min_gram in NGram Tokenizer,"
+                    + "expected difference must be less than or equal to: [" + maxAllowedNgramDiff + "]");
+            }
         }
         this.matcher = parseTokenChars(settings.getAsList("token_chars"));
     }

core/src/main/java/org/elasticsearch/index/analysis/ShingleTokenFilterFactory.java

@@ -22,6 +22,7 @@
 import org.apache.lucene.analysis.TokenStream;
 import org.apache.lucene.analysis.miscellaneous.DisableGraphAttribute;
 import org.apache.lucene.analysis.shingle.ShingleFilter;
+import org.elasticsearch.Version;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.env.Environment;
 import org.elasticsearch.index.IndexSettings;
@@ -35,14 +36,21 @@ public ShingleTokenFilterFactory(IndexSettings indexSettings, Environment enviro
         int maxAllowedShingleDiff = indexSettings.getMaxShingleDiff();
         Integer maxShingleSize = settings.getAsInt("max_shingle_size", ShingleFilter.DEFAULT_MAX_SHINGLE_SIZE);
         Integer minShingleSize = settings.getAsInt("min_shingle_size", ShingleFilter.DEFAULT_MIN_SHINGLE_SIZE);
-        int shingleDiff = maxShingleSize - minShingleSize;
+        Boolean outputUnigrams = settings.getAsBoolean("output_unigrams", true);
+
+        int shingleDiff = maxShingleSize - minShingleSize + (outputUnigrams ? 1 : 0);
         if (shingleDiff > maxAllowedShingleDiff) {
-            throw new IllegalArgumentException(
-                "The difference between max_shingle_size and min_shingle_size in Shingle Token Filter must be less than or equal to: ["
-                    + maxAllowedShingleDiff + "] but was [" + shingleDiff + "]. This limit can be set by changing the ["
-                    + IndexSettings.MAX_SHINGLE_DIFF_SETTING.getKey() + "] index level setting.");
+            if (indexSettings.getIndexVersionCreated().onOrAfter(Version.V_7_0_0_alpha1)) {
+                throw new IllegalArgumentException(
+                    "In Shingle TokenFilter the difference between max_shingle_size and min_shingle_size (and +1 if outputting unigrams)"
+                        + " must be less than or equal to: [" + maxAllowedShingleDiff + "] but was [" + shingleDiff + "]. This limit"
+                        + " can be set by changing the [" + IndexSettings.MAX_SHINGLE_DIFF_SETTING.getKey() + "] index level setting.");
+            } else {
+                deprecationLogger.deprecated("Deprecated big difference between maxShingleSize and minShingleSize in Shingle TokenFilter,"
+                    + "expected difference must be less than or equal to: [" + maxAllowedShingleDiff + "]");
+            }
         }
-        Boolean outputUnigrams = settings.getAsBoolean("output_unigrams", true);
+
         Boolean outputUnigramsIfNoShingles = settings.getAsBoolean("output_unigrams_if_no_shingles", false);
         String tokenSeparator = settings.get("token_separator", ShingleFilter.DEFAULT_TOKEN_SEPARATOR);
         String fillerToken = settings.get("filler_token", ShingleFilter.DEFAULT_FILLER_TOKEN);

core/src/test/java/org/elasticsearch/index/analysis/ShingleTokenFilterFactoryTests.java

@@ -118,9 +118,9 @@ public void testMaxShingleDiffException() throws Exception{
             fail();
         } catch (IllegalArgumentException ex) {
             assertEquals(
-                "The difference between max_shingle_size and min_shingle_size in Shingle Token Filter must be less than or equal to: ["
-                    + maxAllowedShingleDiff + "] but was [" + shingleDiff + "]. This limit can be set by changing the ["
-                    + IndexSettings.MAX_SHINGLE_DIFF_SETTING.getKey() + "] index level setting.",
+                "In Shingle TokenFilter the difference between max_shingle_size and min_shingle_size (and +1 if outputting unigrams)"
+                    + " must be less than or equal to: [" + maxAllowedShingleDiff + "] but was [" + shingleDiff + "]. This limit"
+                    + " can be set by changing the [" + IndexSettings.MAX_SHINGLE_DIFF_SETTING.getKey() + "] index level setting.",
                 ex.getMessage());
         }
     }

core/src/test/java/org/elasticsearch/search/suggest/SuggestSearchIT.java

@@ -28,6 +28,7 @@
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.xcontent.XContentBuilder;
 import org.elasticsearch.common.xcontent.XContentFactory;
+import org.elasticsearch.index.IndexSettings;
 import org.elasticsearch.plugins.Plugin;
 import org.elasticsearch.plugins.ScriptPlugin;
 import org.elasticsearch.script.ScriptContext;
@@ -683,6 +684,7 @@ public void testDifferentShardSize() throws Exception {
     public void testShardFailures() throws IOException, InterruptedException {
         CreateIndexRequestBuilder builder = prepareCreate("test").setSettings(Settings.builder()
                 .put(indexSettings())
+                .put(IndexSettings.MAX_SHINGLE_DIFF_SETTING.getKey(), 4)
                 .put("index.analysis.analyzer.suggest.tokenizer", "standard")
                 .putList("index.analysis.analyzer.suggest.filter", "standard", "lowercase", "shingler")
                 .put("index.analysis.filter.shingler.type", "shingle")
@@ -743,6 +745,7 @@ public void testEmptyShards() throws IOException, InterruptedException {
                 endObject();
         assertAcked(prepareCreate("test").setSettings(Settings.builder()
                 .put(indexSettings())
+                .put(IndexSettings.MAX_SHINGLE_DIFF_SETTING.getKey(), 4)
                 .put("index.analysis.analyzer.suggest.tokenizer", "standard")
                 .putList("index.analysis.analyzer.suggest.filter", "standard", "lowercase", "shingler")
                 .put("index.analysis.filter.shingler.type", "shingle")

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

@@ -13,3 +13,6 @@ type:
 |`max_gram` |Defaults to `2`.
 |============================
 
+The index level setting `index.max_ngram_diff` controls the maximum allowed
+difference between `max_gram` and `min_gram`.
+

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

@@ -38,3 +38,5 @@ used if the position increment is greater than one when a `stop` filter is used
 together with the `shingle` filter. Defaults to `"_"`
 |=======================================================================
 
+The index level setting `index.max_shingle_diff` controls the maximum allowed
+difference between `max_shingle_size` and `min_shingle_size`.

docs/reference/analysis/tokenizers/ngram-tokenizer.asciidoc

@@ -198,6 +198,9 @@ value.  The smaller the length, the more documents will match but the lower
 the quality of the matches.  The longer the length, the more specific the
 matches.  A tri-gram (length `3`) is a good place to start.
 
+The index level setting `index.max_ngram_diff` controls the maximum allowed
+difference between `max_gram` and `min_gram`.
+
 [float]
 === Example configuration
 

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

@@ -25,6 +25,8 @@
 import org.elasticsearch.env.Environment;
 import org.elasticsearch.index.IndexSettings;
 import org.elasticsearch.index.analysis.AbstractTokenFilterFactory;
+import org.elasticsearch.Version;
+
 
 
 public class NGramTokenFilterFactory extends AbstractTokenFilterFactory {
@@ -41,10 +43,15 @@ public class NGramTokenFilterFactory extends AbstractTokenFilterFactory {
         this.maxGram = settings.getAsInt("max_gram", NGramTokenFilter.DEFAULT_MAX_NGRAM_SIZE);
         int ngramDiff = maxGram - minGram;
         if (ngramDiff > maxAllowedNgramDiff) {
-            throw new IllegalArgumentException(
-                "The difference between max_gram and min_gram in NGram Tokenizer must be less than or equal to: [" + maxAllowedNgramDiff
-                    + "] but was [" + ngramDiff + "]. This limit can be set by changing the ["
-                    + IndexSettings.MAX_NGRAM_DIFF_SETTING.getKey() + "] index level setting.");
+            if (indexSettings.getIndexVersionCreated().onOrAfter(Version.V_7_0_0_alpha1)) {
+                throw new IllegalArgumentException(
+                    "The difference between max_gram and min_gram in NGram Tokenizer must be less than or equal to: ["
+                        + maxAllowedNgramDiff + "] but was [" + ngramDiff + "]. This limit can be set by changing the ["
+                        + IndexSettings.MAX_NGRAM_DIFF_SETTING.getKey() + "] index level setting.");
+            } else {
+                deprecationLogger.deprecated("Deprecated big difference between max_gram and min_gram in NGram Tokenizer,"
+                    + "expected difference must be less than or equal to: [" + maxAllowedNgramDiff + "]");
+            }
         }
     }
 

modules/analysis-common/src/test/java/org/elasticsearch/analysis/common/NGramTokenizerFactoryTests.java

@@ -169,16 +169,13 @@ public void testMaxNGramDiffException() throws Exception{
         int max_gram = min_gram + ngramDiff;
 
         final Settings settings = newAnalysisSettingsBuilder().put("min_gram", min_gram).put("max_gram", max_gram).build();
-        try {
-            new NGramTokenizerFactory(indexProperties, null, name, settings).create();
-            fail();
-        } catch (IllegalArgumentException ex) {
-            assertEquals(
-                "The difference between max_gram and min_gram in NGram Tokenizer must be less than or equal to: [" + maxAllowedNgramDiff
-                    + "] but was [" + ngramDiff + "]. This limit can be set by changing the ["
-                    + IndexSettings.MAX_NGRAM_DIFF_SETTING.getKey() + "] index level setting.",
-                ex.getMessage());
-        }
+        IllegalArgumentException ex = expectThrows(IllegalArgumentException.class, () ->
+            new NGramTokenizerFactory(indexProperties, null, name, settings).create());
+        assertEquals(
+            "The difference between max_gram and min_gram in NGram Tokenizer must be less than or equal to: ["
+                + maxAllowedNgramDiff + "] but was [" + ngramDiff + "]. This limit can be set by changing the ["
+                + IndexSettings.MAX_NGRAM_DIFF_SETTING.getKey() + "] index level setting.",
+            ex.getMessage());
     }
 
     private Version randomVersion(Random random) throws IllegalArgumentException, IllegalAccessException {

modules/analysis-common/src/test/resources/rest-api-spec/test/analysis-common/30_tokenizers.yml

@@ -28,6 +28,9 @@
 
 ---
 "nGram_exception":
+    - skip:
+        version: " - 6.99.99"
+        reason: only starting from version 7.x this throws an error
     - do:
         catch: /The difference between max_gram and min_gram in NGram Tokenizer must be less than or equal to[:] \[1\] but was \[2\]\. This limit can be set by changing the \[index.max_ngram_diff\] index level setting\./
         indices.analyze: