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1   /*
2    * Licensed to the Apache Software Foundation (ASF) under one or more
3    * contributor license agreements.  See the NOTICE file distributed with
4    * this work for additional information regarding copyright ownership.
5    * The ASF licenses this file to You under the Apache License, Version 2.0
6    * (the "License"); you may not use this file except in compliance with
7    * the License.  You may obtain a copy of the License at
8    *
9    *     http://www.apache.org/licenses/LICENSE-2.0
10   *
11   * Unless required by applicable law or agreed to in writing, software
12   * distributed under the License is distributed on an "AS IS" BASIS,
13   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   * See the License for the specific language governing permissions and
15   * limitations under the License.
16   */
17  
18  package org.apache.shardingsphere.sql.parser.sql.common.segment.dml.order.item;
19  
20  import lombok.Getter;
21  import lombok.RequiredArgsConstructor;
22  import org.apache.shardingsphere.infra.database.core.metadata.database.DialectDatabaseMetaData;
23  import org.apache.shardingsphere.infra.database.core.metadata.database.enums.NullsOrderType;
24  import org.apache.shardingsphere.infra.database.core.type.DatabaseType;
25  import org.apache.shardingsphere.infra.database.core.type.DatabaseTypeRegistry;
26  import org.apache.shardingsphere.sql.parser.sql.common.enums.OrderDirection;
27  import org.apache.shardingsphere.sql.parser.sql.common.segment.SQLSegment;
28  
29  import java.util.Optional;
30  
31  /**
32   * Order by item segment.
33   */
34  @RequiredArgsConstructor
35  @Getter
36  public abstract class OrderByItemSegment implements SQLSegment {
37      
38      private final int startIndex;
39      
40      private final int stopIndex;
41      
42      private final OrderDirection orderDirection;
43      
44      private final NullsOrderType nullsOrderType;
45      
46      /**
47       * Get nulls order type.
48       *
49       * @return nulls order type
50       */
51      public Optional<NullsOrderType> getNullsOrderType() {
52          return Optional.ofNullable(nullsOrderType);
53      }
54      
55      /**
56       * Get nulls order type.
57       * 
58       * @param databaseType database type
59       * @return nulls order type
60       */
61      public NullsOrderType getNullsOrderType(final DatabaseType databaseType) {
62          if (null != nullsOrderType) {
63              return nullsOrderType;
64          }
65          DialectDatabaseMetaData dialectDatabaseMetaData = new DatabaseTypeRegistry(databaseType).getDialectDatabaseMetaData();
66          return OrderDirection.ASC == orderDirection ? dialectDatabaseMetaData.getDefaultNullsOrderType() : dialectDatabaseMetaData.getDefaultNullsOrderType().getReversedOrderType();
67      }
68  }