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在hbase中，表中可能会存在很多小的region，如果不需要那么多小的region，可以将他们就行合并。

代码的逻辑是将相邻的两个小region进行合并，需要注意以下几点

1、当个region不宜过大，如果两个合并后超过当个region 的最大值，比如7G+7G=14G，超过region配置的最大值10G，这样的话哪怕合并了，也会重新分裂。

2、必须要相邻的两个region，才可以执行命令，不明白原理，不可随意修改代码

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.HBaseConfiguration;
import org.apache.hadoop.hbase.TableName;
import org.apache.hadoop.hbase.client.*;
import org.apache.hadoop.hbase.util.Bytes;
import java.util.ArrayList;public class HbaseMerge {public static void main(String[] args) throws Exception {Configuration config = HBaseConfiguration.create();config.set("hbase.zookeeper.property.clientPort", "2181");config.set("hbase.zookeeper.quorum", "h1,h2,h3");Connection connection = ConnectionFactory.createConnection(config);Table table = connection.getTable(TableName.valueOf("hbase:meta"));//merge表名String tableName = "库名：表名";Admin admin = connection.getAdmin();Scan scan = new Scan();scan.withStartRow(Bytes.toBytes(tableName));scan.withStopRow(Bytes.toBytes(tableName + "_"));ResultScanner scanner = table.getScanner(scan);ArrayList<String> regions = new ArrayList<>();for (Result result : scanner) {String[] split = result.toString().split("\\./");if (split.length > 1) {String s = split[0];String[] split1 = s.split("\\.");String region = split1[split1.length - 1];regions.add(region);}}System.out.println("共有region： " + regions.size() + "个-----------------");for (int i = 0; i < regions.size() - 1; i += 2) {String region1 = regions.get(i);String region2 = regions.get(i + 1);try {admin.mergeRegions(region1.getBytes(), region2.getBytes(), false);System.out.println(region1 + " - " + region2 + " merge is ok");} catch (Exception e) {System.out.println(region1 + " - " + region2 + " merge is fail fail fail");}}//admin.majorCompact(TableName.valueOf(tableName)); 执行major，看是否需要开启admin.close();connection.close();}
}