Remove MinimizationOperations (#17268)

* Remove MinimizationOperations

This class was removed from Lucene because it is no longer needed. It
was copied into the OpenSearch code base because we were using it and
we didn't want our code to break. In fact, the correct choice would
have been to remove the references to
`MinimizationOperations.minimize()` and either replace them with
calls to `Operations.determinize()` or simply drop them altogether
because the automaton is deterministic.

Signed-off-by: Michael Froh <froh@amazon.com>

* Add changelog entry

Signed-off-by: Michael Froh <froh@amazon.com>

---------

Signed-off-by: Michael Froh <froh@amazon.com>

Author: msfroh

CHANGELOG-3.0.md

@@ -34,6 +34,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 - Refactor `:libs` module `bootstrap` package to eliminate top level split packages for JPMS support ([#17117](https://github.com/opensearch-project/OpenSearch/pull/17117))
 - Refactor the codebase to eliminate top level split packages for JPMS support ([#17153](https://github.com/opensearch-project/OpenSearch/pull/17153)
 - Refactor `:server` module `org.apacge.lucene` package to eliminate top level split packages for JPMS support ([#17241](https://github.com/opensearch-project/OpenSearch/pull/17241))
+- Stop minimizing automata used for case-insensitive matches ([#17268](https://github.com/opensearch-project/OpenSearch/pull/17268))
 - Refactor the `:server` module `org.opensearch.client` to `org.opensearch.transport.client` to eliminate top level split packages for JPMS support ([#17272](https://github.com/opensearch-project/OpenSearch/pull/17272))
 
 ### Deprecated

modules/reindex/src/main/java/org/opensearch/index/reindex/ReindexValidator.java

@@ -49,7 +49,6 @@
 import org.opensearch.common.settings.Settings;
 import org.opensearch.core.common.Strings;
 import org.opensearch.index.IndexNotFoundException;
-import org.opensearch.lucene.util.automaton.MinimizationOperations;
 import org.opensearch.search.builder.SearchSourceBuilder;
 
 import java.util.List;
@@ -114,7 +113,7 @@ static CharacterRunAutomaton buildRemoteAllowlist(List<String> allowlist) {
             return new CharacterRunAutomaton(Automata.makeEmpty());
         }
         Automaton automaton = Regex.simpleMatchToAutomaton(allowlist.toArray(Strings.EMPTY_ARRAY));
-        automaton = MinimizationOperations.minimize(automaton, Operations.DEFAULT_DETERMINIZE_WORK_LIMIT);
+        automaton = Operations.determinize(automaton, Operations.DEFAULT_DETERMINIZE_WORK_LIMIT);
         if (Operations.isTotal(automaton)) {
             throw new IllegalArgumentException(
                 "Refusing to start because allowlist "

server/src/main/java/org/opensearch/common/lucene/search/AutomatonQueries.java

@@ -39,7 +39,6 @@
 import org.apache.lucene.util.automaton.Automata;
 import org.apache.lucene.util.automaton.Automaton;
 import org.apache.lucene.util.automaton.Operations;
-import org.opensearch.lucene.util.automaton.MinimizationOperations;
 
 import java.util.ArrayList;
 import java.util.Iterator;
@@ -57,12 +56,12 @@ public static Automaton caseInsensitivePrefix(String s) {
         List<Automaton> list = new ArrayList<>();
         Iterator<Integer> iter = s.codePoints().iterator();
         while (iter.hasNext()) {
-            list.add(toCaseInsensitiveChar(iter.next(), Integer.MAX_VALUE));
+            list.add(toCaseInsensitiveChar(iter.next()));
         }
         list.add(Automata.makeAnyString());
 
         Automaton a = Operations.concatenate(list);
-        a = MinimizationOperations.minimize(a, Integer.MAX_VALUE);
+        assert a.isDeterministic();
         return a;
     }
 
@@ -85,14 +84,14 @@ public static AutomatonQuery caseInsensitivePrefixQuery(Term prefix, MultiTermQu
      */
     public static AutomatonQuery caseInsensitiveTermQuery(Term term) {
         BytesRef prefix = term.bytes();
-        return new AutomatonQuery(term, toCaseInsensitiveString(prefix, Integer.MAX_VALUE));
+        return new AutomatonQuery(term, toCaseInsensitiveString(prefix));
     }
 
     /**
      * Build an automaton matching a wildcard pattern, ASCII case insensitive, if the method is null, then will use {@link  MultiTermQuery#CONSTANT_SCORE_BLENDED_REWRITE}.
      */
     public static AutomatonQuery caseInsensitiveWildcardQuery(Term wildcardquery, MultiTermQuery.RewriteMethod method) {
-        return createAutomatonQuery(wildcardquery, toCaseInsensitiveWildcardAutomaton(wildcardquery, Integer.MAX_VALUE), method);
+        return createAutomatonQuery(wildcardquery, toCaseInsensitiveWildcardAutomaton(wildcardquery), method);
     }
 
     /**
@@ -124,7 +123,7 @@ public static AutomatonQuery createAutomatonQuery(Term term, Automaton automaton
      * Convert Lucene wildcard syntax into an automaton.
      */
     @SuppressWarnings("fallthrough")
-    public static Automaton toCaseInsensitiveWildcardAutomaton(Term wildcardquery, int maxDeterminizedStates) {
+    public static Automaton toCaseInsensitiveWildcardAutomaton(Term wildcardquery) {
         List<Automaton> automata = new ArrayList<>();
 
         String wildcardText = wildcardquery.text();
@@ -148,32 +147,28 @@ public static Automaton toCaseInsensitiveWildcardAutomaton(Term wildcardquery, i
                         break;
                     } // else fallthru, lenient parsing with a trailing \
                 default:
-                    automata.add(toCaseInsensitiveChar(c, maxDeterminizedStates));
+                    automata.add(toCaseInsensitiveChar(c));
             }
             i += length;
         }
 
         return Operations.concatenate(automata);
     }
 
-    protected static Automaton toCaseInsensitiveString(BytesRef br, int maxDeterminizedStates) {
-        return toCaseInsensitiveString(br.utf8ToString(), maxDeterminizedStates);
+    protected static Automaton toCaseInsensitiveString(BytesRef br) {
+        return toCaseInsensitiveString(br.utf8ToString());
     }
 
-    public static Automaton toCaseInsensitiveString(String s, int maxDeterminizedStates) {
+    public static Automaton toCaseInsensitiveString(String s) {
         List<Automaton> list = new ArrayList<>();
         Iterator<Integer> iter = s.codePoints().iterator();
         while (iter.hasNext()) {
-            list.add(toCaseInsensitiveChar(iter.next(), maxDeterminizedStates));
+            list.add(toCaseInsensitiveChar(iter.next()));
         }
-
-        Automaton a = Operations.concatenate(list);
-        a = MinimizationOperations.minimize(a, maxDeterminizedStates);
-        return a;
-
+        return Operations.concatenate(list);
     }
 
-    public static Automaton toCaseInsensitiveChar(int codepoint, int maxDeterminizedStates) {
+    public static Automaton toCaseInsensitiveChar(int codepoint) {
         Automaton case1 = Automata.makeChar(codepoint);
         // For now we only work with ASCII characters
         if (codepoint > 128) {
@@ -183,7 +178,6 @@ public static Automaton toCaseInsensitiveChar(int codepoint, int maxDeterminized
         Automaton result;
         if (altCase != codepoint) {
             result = Operations.union(case1, Automata.makeChar(altCase));
-            result = MinimizationOperations.minimize(result, maxDeterminizedStates);
         } else {
             result = case1;
         }

server/src/main/java/org/opensearch/index/mapper/KeywordFieldMapper.java

@@ -411,7 +411,7 @@ public Query termQueryCaseInsensitive(Object value, QueryShardContext context) {
                 Term term = new Term(name(), bytesRef);
                 Query query = AutomatonQueries.createAutomatonQuery(
                     term,
-                    AutomatonQueries.toCaseInsensitiveString(bytesRef.utf8ToString(), Operations.DEFAULT_DETERMINIZE_WORK_LIMIT),
+                    AutomatonQueries.toCaseInsensitiveString(bytesRef.utf8ToString()),
                     MultiTermQuery.DOC_VALUES_REWRITE
                 );
                 if (boost() != 1f) {

server/src/main/java/org/opensearch/index/mapper/TextFieldMapper.java

@@ -640,7 +640,7 @@ public Query prefixQuery(String value, MultiTermQuery.RewriteMethod method, bool
             }
             List<Automaton> automata = new ArrayList<>();
             if (caseInsensitive) {
-                automata.add(AutomatonQueries.toCaseInsensitiveString(value, Integer.MAX_VALUE));
+                automata.add(AutomatonQueries.toCaseInsensitiveString(value));
             } else {
                 automata.add(Automata.makeString(value));
             }

server/src/main/java/org/opensearch/indices/SystemIndices.java

@@ -41,7 +41,6 @@
 import org.opensearch.common.Nullable;
 import org.opensearch.common.regex.Regex;
 import org.opensearch.core.index.Index;
-import org.opensearch.lucene.util.automaton.MinimizationOperations;
 
 import java.util.Collection;
 import java.util.List;
@@ -147,6 +146,8 @@ private static CharacterRunAutomaton buildCharacterRunAutomaton(Collection<Syste
         Optional<Automaton> automaton = descriptors.stream()
             .map(descriptor -> Regex.simpleMatchToAutomaton(descriptor.getIndexPattern()))
             .reduce(Operations::union);
-        return new CharacterRunAutomaton(MinimizationOperations.minimize(automaton.orElse(Automata.makeEmpty()), Integer.MAX_VALUE));
+        return new CharacterRunAutomaton(
+            Operations.determinize(automaton.orElse(Automata.makeEmpty()), Operations.DEFAULT_DETERMINIZE_WORK_LIMIT)
+        );
     }
 }