docs/attachments/LUCENE-8601/LUCENE-8601.03.patch

diff --git a/lucene/core/src/java/org/apache/lucene/document/FieldType.java b/lucene/core/src/java/org/apache/lucene/document/FieldType.java
index a21572e96c..cdf01e1626 100644
--- a/lucene/core/src/java/org/apache/lucene/document/FieldType.java
+++ b/lucene/core/src/java/org/apache/lucene/document/FieldType.java
@@ -17,6 +17,9 @@
 package org.apache.lucene.document;
 
 
+import java.util.HashMap;
+import java.util.Map;
+
 import org.apache.lucene.analysis.Analyzer; // javadocs
 import org.apache.lucene.index.DocValuesType;
 import org.apache.lucene.index.IndexOptions;
@@ -41,6 +44,7 @@ public class FieldType implements IndexableFieldType  {
   private int dataDimensionCount;
   private int indexDimensionCount;
   private int dimensionNumBytes;
+  private Map<String, String> attributes = null;
 
   /**
    * Create a new mutable FieldType with all of the properties from <code>ref</code>
@@ -58,6 +62,7 @@ public class FieldType implements IndexableFieldType  {
     this.dataDimensionCount = ref.pointDataDimensionCount();
     this.indexDimensionCount = ref.pointIndexDimensionCount();
     this.dimensionNumBytes = ref.pointNumBytes();
+    this.attributes = ref.getAttributes();
     // Do not copy frozen!
   }
   
@@ -341,6 +346,30 @@ public class FieldType implements IndexableFieldType  {
     return dimensionNumBytes;
   }
 
+  /**
+   * Puts an attribute value.
+   * <p>
+   * This is a key-value mapping for the field that the codec can use
+   * to store additional metadata.
+   * <p>
+   * If a value already exists for the field, it will be replaced with
+   * the new value. This method is not thread-safe, user must not add attributes
+   * while other threads are indexing documents with this field type.
+   *
+   * @lucene.experimental
+   */
+  public String putAttribute(String key, String value) {
+    if (attributes == null) {
+      attributes = new HashMap<>();
+    }
+    return attributes.put(key, value);
+  }
+
+  @Override
+  public Map<String, String> getAttributes() {
+    return attributes;
+  }
+
   /** Prints a Field for human consumption. */
   @Override
   public String toString() {
diff --git a/lucene/core/src/java/org/apache/lucene/index/DefaultIndexingChain.java b/lucene/core/src/java/org/apache/lucene/index/DefaultIndexingChain.java
index 4cc981dbd7..91a69cf2f1 100644
--- a/lucene/core/src/java/org/apache/lucene/index/DefaultIndexingChain.java
+++ b/lucene/core/src/java/org/apache/lucene/index/DefaultIndexingChain.java
@@ -661,6 +661,10 @@ final class DefaultIndexingChain extends DocConsumer {
 
       FieldInfo fi = fieldInfos.getOrAdd(name);
       initIndexOptions(fi, fieldType.indexOptions());
+      if (fieldType.getAttributes() != null) {
+        fieldType.getAttributes().forEach((k, v) -> fi.putAttribute(k, v));
+      }
+
       fp = new PerField(docWriter.getIndexCreatedVersionMajor(), fi, invert);
       fp.next = fieldHash[hashPos];
       fieldHash[hashPos] = fp;
diff --git a/lucene/core/src/java/org/apache/lucene/index/IndexableFieldType.java b/lucene/core/src/java/org/apache/lucene/index/IndexableFieldType.java
index b2b2e773ca..59c5ab5192 100644
--- a/lucene/core/src/java/org/apache/lucene/index/IndexableFieldType.java
+++ b/lucene/core/src/java/org/apache/lucene/index/IndexableFieldType.java
@@ -17,6 +17,8 @@
 package org.apache.lucene.index;
 
 
+import java.util.Map;
+
 import org.apache.lucene.analysis.Analyzer; // javadocs
 
 /** 
@@ -111,4 +113,14 @@ public interface IndexableFieldType {
    * The number of bytes in each dimension's values.
    */
   public int pointNumBytes();
+
+  /**
+   * Attributes for the field type.
+   *
+   * Attributes are not thread-safe, user must not add attributes while other threads are indexing documents
+   * with this field type.
+   *
+   * @return Map
+   */
+  public Map<String, String> getAttributes();
 }
diff --git a/lucene/core/src/test/org/apache/lucene/index/TestFieldInfos.java b/lucene/core/src/test/org/apache/lucene/index/TestFieldInfos.java
index 3fe5fa9d2c..79fb5abae7 100644
--- a/lucene/core/src/test/org/apache/lucene/index/TestFieldInfos.java
+++ b/lucene/core/src/test/org/apache/lucene/index/TestFieldInfos.java
@@ -23,6 +23,7 @@ import java.util.Iterator;
 import org.apache.lucene.analysis.MockAnalyzer;
 import org.apache.lucene.document.Document;
 import org.apache.lucene.document.Field;
+import org.apache.lucene.document.FieldType;
 import org.apache.lucene.document.StringField;
 import org.apache.lucene.store.Directory;
 import org.apache.lucene.util.LuceneTestCase;
@@ -93,6 +94,32 @@ public class TestFieldInfos extends LuceneTestCase {
     dir.close();
   }
 
+  public void testFieldAttributes() throws Exception{
+    Directory dir = newDirectory();
+    IndexWriter writer = new IndexWriter(dir, newIndexWriterConfig(new MockAnalyzer(random()))
+        .setMergePolicy(NoMergePolicy.INSTANCE));
+
+    Document d = new Document();
+    FieldType type = new FieldType();
+    type.setStored(true);
+    type.putAttribute("testKey", "testValue");
+    d.add(new Field("f", "v", type));
+    writer.addDocument(d);
+    writer.commit();
+    writer.close();
+
+    SegmentInfos sis = SegmentInfos.readLatestCommit(dir);
+    FieldInfos fis = IndexWriter.readFieldInfos(sis.info(0));
+    Iterator<FieldInfo>  it = fis.iterator();
+    while(it.hasNext()) {
+      FieldInfo fi = it.next();
+      assertEquals(0, fi.number);
+      assertEquals("f", fi.name);
+      assertEquals("testValue", fi.getAttribute("testKey"));
+    }
+    dir.close();
+  }
+
   public void testMergedFieldInfos_empty() throws IOException {
     Directory dir = newDirectory();
     IndexWriter writer = new IndexWriter(dir, newIndexWriterConfig(new MockAnalyzer(random())));
diff --git a/lucene/core/src/test/org/apache/lucene/index/TestIndexableField.java b/lucene/core/src/test/org/apache/lucene/index/TestIndexableField.java
index 1091b2485e..59dbae3cd7 100644
--- a/lucene/core/src/test/org/apache/lucene/index/TestIndexableField.java
+++ b/lucene/core/src/test/org/apache/lucene/index/TestIndexableField.java
@@ -21,6 +21,7 @@ import java.io.Reader;
 import java.io.StringReader;
 import java.util.Collections;
 import java.util.Iterator;
+import java.util.Map;
 
 import org.apache.lucene.analysis.Analyzer;
 import org.apache.lucene.analysis.TokenStream;
@@ -104,6 +105,11 @@ public class TestIndexableField extends LuceneTestCase {
       public int pointNumBytes() {
         return 0;
       }
+
+      @Override
+      public Map<String, String> getAttributes() {
+        return null;
+      }
     };
 
     public MyField(int counter) {
diff --git a/solr/core/src/java/org/apache/solr/schema/SchemaField.java b/solr/core/src/java/org/apache/solr/schema/SchemaField.java
index 7d9449e6d9..100a963c1c 100644
--- a/solr/core/src/java/org/apache/solr/schema/SchemaField.java
+++ b/solr/core/src/java/org/apache/solr/schema/SchemaField.java
@@ -430,4 +430,9 @@ public final class SchemaField extends FieldProperties implements IndexableField
   public int pointNumBytes() {
     return 0;
   }
+
+  @Override
+  public Map<String, String> getAttributes() {
+    return null;
+  }
 }