[HUDI-2176, 2178, 2179] Adding virtual key support to COW table (#3306)

hudi-common/src/main/java/org/apache/hudi/avro/HoodieAvroUtils.java

@@ -244,6 +244,22 @@ public class HoodieAvroUtils {
     return recordSchema;
   }
 
+  /**
+   * Fetch schema for record key and partition path.
+   */
+  public static Schema getSchemaForFields(Schema fileSchema, List<String> fields) {
+    List<Schema.Field> toBeAddedFields = new ArrayList<>();
+    Schema recordSchema = Schema.createRecord("HoodieRecordKey", "", "", false);
+
+    for (Schema.Field schemaField: fileSchema.getFields()) {
+      if (fields.contains(schemaField.name())) {
+        toBeAddedFields.add(new Schema.Field(schemaField.name(), schemaField.schema(), schemaField.doc(), schemaField.defaultValue()));
+      }
+    }
+    recordSchema.setFields(toBeAddedFields);
+    return recordSchema;
+  }
+
   public static GenericRecord addHoodieKeyToRecord(GenericRecord record, String recordKey, String partitionPath,
       String fileName) {
     record.put(HoodieRecord.FILENAME_METADATA_FIELD, fileName);

hudi-common/src/main/java/org/apache/hudi/avro/HoodieAvroWriteSupport.java

@@ -20,6 +20,7 @@ package org.apache.hudi.avro;
 
 import org.apache.hudi.common.bloom.BloomFilter;
 import org.apache.hudi.common.bloom.HoodieDynamicBoundedBloomFilter;
+import org.apache.hudi.common.util.Option;
 
 import org.apache.avro.Schema;
 import org.apache.parquet.avro.AvroWriteSupport;
@@ -33,7 +34,7 @@ import java.util.HashMap;
  */
 public class HoodieAvroWriteSupport extends AvroWriteSupport {
 
-  private BloomFilter bloomFilter;
+  private Option<BloomFilter> bloomFilterOpt;
   private String minRecordKey;
   private String maxRecordKey;
 
@@ -44,39 +45,41 @@ public class HoodieAvroWriteSupport extends AvroWriteSupport {
   public static final String HOODIE_BLOOM_FILTER_TYPE_CODE = "hoodie_bloom_filter_type_code";
   public static final String HOODIE_AVRO_SCHEMA_METADATA_KEY = "orc.avro.schema";
 
-  public HoodieAvroWriteSupport(MessageType schema, Schema avroSchema, BloomFilter bloomFilter) {
+  public HoodieAvroWriteSupport(MessageType schema, Schema avroSchema, Option<BloomFilter> bloomFilterOpt) {
     super(schema, avroSchema);
-    this.bloomFilter = bloomFilter;
+    this.bloomFilterOpt = bloomFilterOpt;
   }
 
   @Override
   public WriteSupport.FinalizedWriteContext finalizeWrite() {
     HashMap<String, String> extraMetaData = new HashMap<>();
-    if (bloomFilter != null) {
-      extraMetaData.put(HOODIE_AVRO_BLOOM_FILTER_METADATA_KEY, bloomFilter.serializeToString());
+    if (bloomFilterOpt.isPresent()) {
+      extraMetaData.put(HOODIE_AVRO_BLOOM_FILTER_METADATA_KEY, bloomFilterOpt.get().serializeToString());
       if (minRecordKey != null && maxRecordKey != null) {
         extraMetaData.put(HOODIE_MIN_RECORD_KEY_FOOTER, minRecordKey);
         extraMetaData.put(HOODIE_MAX_RECORD_KEY_FOOTER, maxRecordKey);
       }
-      if (bloomFilter.getBloomFilterTypeCode().name().contains(HoodieDynamicBoundedBloomFilter.TYPE_CODE_PREFIX)) {
-        extraMetaData.put(HOODIE_BLOOM_FILTER_TYPE_CODE, bloomFilter.getBloomFilterTypeCode().name());
+      if (bloomFilterOpt.get().getBloomFilterTypeCode().name().contains(HoodieDynamicBoundedBloomFilter.TYPE_CODE_PREFIX)) {
+        extraMetaData.put(HOODIE_BLOOM_FILTER_TYPE_CODE, bloomFilterOpt.get().getBloomFilterTypeCode().name());
       }
     }
     return new WriteSupport.FinalizedWriteContext(extraMetaData);
   }
 
   public void add(String recordKey) {
-    this.bloomFilter.add(recordKey);
-    if (minRecordKey != null) {
-      minRecordKey = minRecordKey.compareTo(recordKey) <= 0 ? minRecordKey : recordKey;
-    } else {
-      minRecordKey = recordKey;
-    }
+    if (bloomFilterOpt.isPresent()) {
+      this.bloomFilterOpt.get().add(recordKey);
+      if (minRecordKey != null) {
+        minRecordKey = minRecordKey.compareTo(recordKey) <= 0 ? minRecordKey : recordKey;
+      } else {
+        minRecordKey = recordKey;
+      }
 
-    if (maxRecordKey != null) {
-      maxRecordKey = maxRecordKey.compareTo(recordKey) >= 0 ? maxRecordKey : recordKey;
-    } else {
-      maxRecordKey = recordKey;
+      if (maxRecordKey != null) {
+        maxRecordKey = maxRecordKey.compareTo(recordKey) >= 0 ? maxRecordKey : recordKey;
+      } else {
+        maxRecordKey = recordKey;
+      }
     }
   }
 }

hudi-common/src/main/java/org/apache/hudi/common/table/HoodieTableMetaClient.java

@@ -319,12 +319,6 @@ public class HoodieTableMetaClient implements Serializable {
    * @param operationType operation type to be executed.
    */
   public void validateTableProperties(Properties properties, WriteOperationType operationType) {
-    // disabling meta fields are allowed only for bulk_insert operation
-    if (!Boolean.parseBoolean((String) properties.getOrDefault(HoodieTableConfig.HOODIE_POPULATE_META_FIELDS.key(), HoodieTableConfig.HOODIE_POPULATE_META_FIELDS.defaultValue()))
-        && operationType != WriteOperationType.BULK_INSERT) {
-      throw new HoodieException(HoodieTableConfig.HOODIE_POPULATE_META_FIELDS.key() + " can only be disabled for " + WriteOperationType.BULK_INSERT
-          + " operation");
-    }
     // once meta fields are disabled, it cant be re-enabled for a given table.
     if (!getTableConfig().populateMetaFields()
         && Boolean.parseBoolean((String) properties.getOrDefault(HoodieTableConfig.HOODIE_POPULATE_META_FIELDS.key(), HoodieTableConfig.HOODIE_POPULATE_META_FIELDS.defaultValue()))) {

hudi-common/src/main/java/org/apache/hudi/common/util/BaseFileUtils.java

@@ -34,6 +34,7 @@ import org.apache.hudi.common.model.HoodieFileFormat;
 import org.apache.hudi.common.model.HoodieKey;
 import org.apache.hudi.common.table.HoodieTableMetaClient;
 import org.apache.hudi.exception.HoodieException;
+import org.apache.hudi.keygen.BaseKeyGenerator;
 
 public abstract class BaseFileUtils {
 
@@ -170,6 +171,15 @@ public abstract class BaseFileUtils {
    */
   public abstract List<HoodieKey> fetchRecordKeyPartitionPath(Configuration configuration, Path filePath);
 
+  /**
+   * Fetch {@link HoodieKey}s from the given data file.
+   * @param configuration configuration to build fs object
+   * @param filePath      The data file path
+   * @param keyGeneratorOpt instance of KeyGenerator.
+   * @return {@link List} of {@link HoodieKey}s fetched from the parquet file
+   */
+  public abstract List<HoodieKey> fetchRecordKeyPartitionPath(Configuration configuration, Path filePath, Option<BaseKeyGenerator> keyGeneratorOpt);
+
   /**
    * Read the Avro schema of the data file.
    * @param configuration Configuration

hudi-common/src/main/java/org/apache/hudi/common/util/OrcUtils.java

@@ -41,6 +41,8 @@ import org.apache.hudi.common.model.HoodieRecord;
 import org.apache.hudi.exception.HoodieException;
 import org.apache.hudi.exception.HoodieIOException;
 import org.apache.hudi.exception.MetadataNotFoundException;
+import org.apache.hudi.keygen.BaseKeyGenerator;
+
 import org.apache.orc.OrcFile;
 import org.apache.orc.OrcProto.UserMetadataItem;
 import org.apache.orc.Reader;
@@ -109,6 +111,11 @@ public class OrcUtils extends BaseFileUtils {
     return hoodieKeys;
   }
 
+  @Override
+  public List<HoodieKey> fetchRecordKeyPartitionPath(Configuration configuration, Path filePath, Option<BaseKeyGenerator> keyGeneratorOpt) {
+    throw new HoodieIOException("UnsupportedOperation : Disabling meta fields not yet supported for Orc");
+  }
+
   /**
    * NOTE: This literally reads the entire file contents, thus should be used with caution.
    */

hudi-common/src/main/java/org/apache/hudi/common/util/ParquetUtils.java

@@ -24,6 +24,7 @@ import org.apache.hudi.common.model.HoodieKey;
 import org.apache.hudi.common.model.HoodieRecord;
 import org.apache.hudi.exception.HoodieIOException;
 import org.apache.hudi.exception.MetadataNotFoundException;
+import org.apache.hudi.keygen.BaseKeyGenerator;
 
 import org.apache.avro.Schema;
 import org.apache.avro.generic.GenericRecord;
@@ -115,23 +116,36 @@ public class ParquetUtils extends BaseFileUtils {
    */
   @Override
   public List<HoodieKey> fetchRecordKeyPartitionPath(Configuration configuration, Path filePath) {
+    return fetchRecordKeyPartitionPathInternal(configuration, filePath, Option.empty());
+  }
+
+  private List<HoodieKey> fetchRecordKeyPartitionPathInternal(Configuration configuration, Path filePath, Option<BaseKeyGenerator> keyGeneratorOpt) {
     List<HoodieKey> hoodieKeys = new ArrayList<>();
     try {
-      if (!filePath.getFileSystem(configuration).exists(filePath)) {
-        return new ArrayList<>();
-      }
-
       Configuration conf = new Configuration(configuration);
       conf.addResource(FSUtils.getFs(filePath.toString(), conf).getConf());
-      Schema readSchema = HoodieAvroUtils.getRecordKeyPartitionPathSchema();
+      Schema readSchema = keyGeneratorOpt.map(keyGenerator -> {
+        List<String> fields = new ArrayList<>();
+        fields.addAll(keyGenerator.getRecordKeyFields());
+        fields.addAll(keyGenerator.getPartitionPathFields());
+        return HoodieAvroUtils.getSchemaForFields(readAvroSchema(conf, filePath), fields);
+      })
+          .orElse(HoodieAvroUtils.getRecordKeyPartitionPathSchema());
       AvroReadSupport.setAvroReadSchema(conf, readSchema);
       AvroReadSupport.setRequestedProjection(conf, readSchema);
       ParquetReader reader = AvroParquetReader.builder(filePath).withConf(conf).build();
       Object obj = reader.read();
       while (obj != null) {
         if (obj instanceof GenericRecord) {
-          String recordKey = ((GenericRecord) obj).get(HoodieRecord.RECORD_KEY_METADATA_FIELD).toString();
-          String partitionPath = ((GenericRecord) obj).get(HoodieRecord.PARTITION_PATH_METADATA_FIELD).toString();
+          String recordKey = null;
+          String partitionPath = null;
+          if (keyGeneratorOpt.isPresent()) {
+            recordKey = keyGeneratorOpt.get().getRecordKey((GenericRecord) obj);
+            partitionPath = keyGeneratorOpt.get().getPartitionPath((GenericRecord) obj);
+          } else {
+            recordKey = ((GenericRecord) obj).get(HoodieRecord.RECORD_KEY_METADATA_FIELD).toString();
+            partitionPath = ((GenericRecord) obj).get(HoodieRecord.PARTITION_PATH_METADATA_FIELD).toString();
+          }
           hoodieKeys.add(new HoodieKey(recordKey, partitionPath));
           obj = reader.read();
         }
@@ -142,6 +156,19 @@ public class ParquetUtils extends BaseFileUtils {
     return hoodieKeys;
   }
 
+  /**
+   * Fetch {@link HoodieKey}s from the given parquet file.
+   *
+   * @param configuration   configuration to build fs object
+   * @param filePath        The parquet file path.
+   * @param keyGeneratorOpt
+   * @return {@link List} of {@link HoodieKey}s fetched from the parquet file
+   */
+  @Override
+  public List<HoodieKey> fetchRecordKeyPartitionPath(Configuration configuration, Path filePath, Option<BaseKeyGenerator> keyGeneratorOpt) {
+    return fetchRecordKeyPartitionPathInternal(configuration, filePath, keyGeneratorOpt);
+  }
+
   public ParquetMetadata readMetadata(Configuration conf, Path parquetFilePath) {
     ParquetMetadata footer;
     try {
@@ -223,7 +250,7 @@ public class ParquetUtils extends BaseFileUtils {
   /**
    * Returns the number of records in the parquet file.
    *
-   * @param conf Configuration
+   * @param conf            Configuration
    * @param parquetFilePath path of the file
    */
   @Override

hudi-common/src/main/java/org/apache/hudi/keygen/BaseKeyGenerator.java

@@ -0,0 +1,81 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF 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.apache.hudi.keygen;
+
+import org.apache.avro.generic.GenericRecord;
+import org.apache.hudi.common.config.TypedProperties;
+import org.apache.hudi.common.model.HoodieKey;
+import org.apache.hudi.exception.HoodieKeyException;
+import org.apache.hudi.keygen.constant.KeyGeneratorOptions;
+
+import java.util.List;
+import java.util.stream.Collectors;
+
+public abstract class BaseKeyGenerator extends KeyGenerator {
+
+  protected List<String> recordKeyFields;
+  protected List<String> partitionPathFields;
+  protected final boolean encodePartitionPath;
+  protected final boolean hiveStylePartitioning;
+
+  protected BaseKeyGenerator(TypedProperties config) {
+    super(config);
+    this.encodePartitionPath = config.getBoolean(KeyGeneratorOptions.URL_ENCODE_PARTITIONING_OPT_KEY.key(),
+        Boolean.parseBoolean(KeyGeneratorOptions.URL_ENCODE_PARTITIONING_OPT_KEY.defaultValue()));
+    this.hiveStylePartitioning = config.getBoolean(KeyGeneratorOptions.HIVE_STYLE_PARTITIONING_OPT_KEY.key(),
+        Boolean.parseBoolean(KeyGeneratorOptions.HIVE_STYLE_PARTITIONING_OPT_KEY.defaultValue()));
+  }
+
+  /**
+   * Generate a record Key out of provided generic record.
+   */
+  public abstract String getRecordKey(GenericRecord record);
+
+  /**
+   * Generate a partition path out of provided generic record.
+   */
+  public abstract String getPartitionPath(GenericRecord record);
+
+  /**
+   * Generate a Hoodie Key out of provided generic record.
+   */
+  @Override
+  public final HoodieKey getKey(GenericRecord record) {
+    if (getRecordKeyFields() == null || getPartitionPathFields() == null) {
+      throw new HoodieKeyException("Unable to find field names for record key or partition path in cfg");
+    }
+    return new HoodieKey(getRecordKey(record), getPartitionPath(record));
+  }
+
+  @Override
+  public final List<String> getRecordKeyFieldNames() {
+    // For nested columns, pick top level column name
+    return getRecordKeyFields().stream().map(k -> {
+      int idx = k.indexOf('.');
+      return idx > 0 ? k.substring(0, idx) : k;
+    }).collect(Collectors.toList());
+  }
+
+  public List<String> getRecordKeyFields() {
+    return recordKeyFields;
+  }
+
+  public List<String> getPartitionPathFields() {
+    return partitionPathFields;
+  }
+}

hudi-common/src/main/java/org/apache/hudi/keygen/KeyGenerator.java

@@ -0,0 +1,59 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF 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.apache.hudi.keygen;
+
+import org.apache.hudi.ApiMaturityLevel;
+import org.apache.hudi.PublicAPIClass;
+import org.apache.hudi.PublicAPIMethod;
+import org.apache.hudi.common.config.TypedProperties;
+import org.apache.hudi.common.model.HoodieKey;
+
+import org.apache.avro.generic.GenericRecord;
+
+import java.util.List;
+
+/**
+ * Abstract class to extend for plugging in extraction of {@link HoodieKey} from an Avro record.
+ */
+@PublicAPIClass(maturity = ApiMaturityLevel.STABLE)
+public abstract class KeyGenerator implements KeyGeneratorInterface {
+
+  protected TypedProperties config;
+
+  protected KeyGenerator(TypedProperties config) {
+    this.config = config;
+  }
+
+  /**
+   * Generate a Hoodie Key out of provided generic record.
+   */
+  @PublicAPIMethod(maturity = ApiMaturityLevel.STABLE)
+  public abstract HoodieKey getKey(GenericRecord record);
+
+  /**
+   * Used during bootstrap, to project out only the record key fields from bootstrap source dataset.
+   *
+   * @return list of field names, when concatenated make up the record key.
+   */
+  @PublicAPIMethod(maturity = ApiMaturityLevel.EVOLVING)
+  public List<String> getRecordKeyFieldNames() {
+    throw new UnsupportedOperationException("Bootstrap not supported for key generator. "
+        + "Please override this method in your custom key generator.");
+  }
+}

hudi-common/src/main/java/org/apache/hudi/keygen/KeyGeneratorInterface.java

@@ -0,0 +1,36 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF 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.apache.hudi.keygen;
+
+import org.apache.avro.generic.GenericRecord;
+import org.apache.hudi.common.model.HoodieKey;
+
+import java.io.Serializable;
+import java.util.List;
+
+/**
+ * Represents the interface key generators need to adhere to.
+ */
+public interface KeyGeneratorInterface extends Serializable {
+
+  HoodieKey getKey(GenericRecord record);
+
+  List<String> getRecordKeyFieldNames();
+
+}

hudi-common/src/main/java/org/apache/hudi/keygen/constant/KeyGeneratorOptions.java

@@ -0,0 +1,59 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF 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.apache.hudi.keygen.constant;
+
+import org.apache.hudi.common.config.ConfigClassProperty;
+import org.apache.hudi.common.config.ConfigGroups;
+import org.apache.hudi.common.config.ConfigProperty;
+import org.apache.hudi.common.config.HoodieConfig;
+
+@ConfigClassProperty(name = "Key Generator Options",
+    groupName = ConfigGroups.Names.WRITE_CLIENT,
+    description = "Hudi maintains keys (record key + partition path) "
+        + "for uniquely identifying a particular record. "
+        + "This config allows developers to setup the Key generator class that "
+        + "will extract these out of incoming records.")
+public class KeyGeneratorOptions extends HoodieConfig {
+
+  public static final ConfigProperty<String> URL_ENCODE_PARTITIONING_OPT_KEY = ConfigProperty
+      .key("hoodie.datasource.write.partitionpath.urlencode")
+      .defaultValue("false")
+      .withDocumentation("Should we url encode the partition path value, before creating the folder structure.");
+
+  public static final ConfigProperty<String> HIVE_STYLE_PARTITIONING_OPT_KEY = ConfigProperty
+      .key("hoodie.datasource.write.hive_style_partitioning")
+      .defaultValue("false")
+      .withDocumentation("Flag to indicate whether to use Hive style partitioning.\n"
+          + "If set true, the names of partition folders follow <partition_column_name>=<partition_value> format.\n"
+          + "By default false (the names of partition folders are only partition values)");
+
+  public static final ConfigProperty<String> RECORDKEY_FIELD_OPT_KEY = ConfigProperty
+      .key("hoodie.datasource.write.recordkey.field")
+      .defaultValue("uuid")
+      .withDocumentation("Record key field. Value to be used as the `recordKey` component of `HoodieKey`.\n"
+          + "Actual value will be obtained by invoking .toString() on the field value. Nested fields can be specified using\n"
+          + "the dot notation eg: `a.b.c`");
+
+  public static final ConfigProperty<String> PARTITIONPATH_FIELD_OPT_KEY = ConfigProperty
+      .key("hoodie.datasource.write.partitionpath.field")
+      .defaultValue("partitionpath")
+      .withDocumentation("Partition path field. Value to be used at the partitionPath component of HoodieKey. "
+          + "Actual value ontained by invoking .toString()");
+}
+

hudi-common/src/main/java/org/apache/hudi/keygen/constant/KeyGeneratorType.java

@@ -0,0 +1,70 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF 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.apache.hudi.keygen.constant;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+/**
+ * Types of {@link org.apache.hudi.keygen.KeyGenerator}.
+ */
+public enum KeyGeneratorType {
+  /**
+   * Simple key generator, which takes names of fields to be used for recordKey and partitionPath as configs.
+   */
+  SIMPLE,
+
+  /**
+   * Complex key generator, which takes names of fields to be used for recordKey and partitionPath as configs.
+   */
+  COMPLEX,
+
+  /**
+   * Key generator, that relies on timestamps for partitioning field. Still picks record key by name.
+   */
+  TIMESTAMP,
+
+  /**
+   * This is a generic implementation type of KeyGenerator where users can configure record key as a single field or
+   * a combination of fields. Similarly partition path can be configured to have multiple fields or only one field.
+   * <p>
+   * This KeyGenerator expects value for prop "hoodie.datasource.write.partitionpath.field" in a specific format.
+   * For example:
+   * properties.put("hoodie.datasource.write.partitionpath.field", "field1:PartitionKeyType1,field2:PartitionKeyType2").
+   */
+  CUSTOM,
+
+  /**
+   * Simple Key generator for unpartitioned Hive Tables.
+   */
+  NON_PARTITION,
+
+  /**
+   * Key generator for deletes using global indices.
+   */
+  GLOBAL_DELETE;
+
+  public static List<String> getNames() {
+    List<String> names = new ArrayList<>(KeyGeneratorType.values().length);
+    Arrays.stream(KeyGeneratorType.values())
+        .forEach(x -> names.add(x.name()));
+    return names;
+  }
+}