创建HBase表

功能简介

HBase通过org.apache.hadoop.hbase.client.Admin对象的createTable方法来创建表，并指定表名、列族名。创建表有两种方式，建议采用预分Region建表方式：

• 快速建表，即创建表后整张表只有一个Region，随着数据量的增加会自动分裂成多个Region。
• 预分Region建表，即创建表时预先分配多个Region，此种方法建表可以提高写入大量数据初期的数据写入速度。

表的列名以及列族名不能包含特殊字符，可以由字母、数字以及下划线组成。

代码样例

以下代码片段在com.huawei.bigdata.hbase.examples包的“HBaseExample”类的testCreateTable方法中

public void testCreateTable() {
    LOG.info("Entering testCreateTable: " + tableName);

     // Set the column family name to info.
     byte [] fam = Bytes.toBytes("info");
     ColumnFamilyDescriptor familyDescriptor = ColumnFamilyDescriptorBuilder.newBuilder(fam)
             // Set data encoding methods. HBase provides DIFF,FAST_DIFF,PREFIX
             // HBase 2.0 removed `PREFIX_TREE` Data Block Encoding from column families.
             .setDataBlockEncoding(DataBlockEncoding.FAST_DIFF)
             // Set compression methods, HBase provides two default compression
             // methods:GZ and SNAPPY
             // GZ has the highest compression rate,but low compression and
             // decompression effeciency,fit for cold data
             // SNAPPY has low compression rate, but high compression and
             // decompression effeciency,fit for hot data.
             // it is advised to use SANPPY
             .setCompressionType(Compression.Algorithm.SNAPPY)
             .build();
     TableDescriptor htd = TableDescriptorBuilder.newBuilder(tableName).setColumnFamily(familyDescriptor).build();

     Admin admin = null;
     try {
         // Instantiate an Admin object.
         admin = conn.getAdmin();
         if (!admin.tableExists(tableName)) {
             LOG.info("Creating table...");
             admin.createTable(htd);
             LOG.info(admin.getClusterMetrics());
             LOG.info(admin.listNamespaceDescriptors());
             LOG.info("Table created successfully.");
         } else {
             LOG.warn("table already exists");
         }
     } catch (IOException e) {
         LOG.error("Create table failed.", e);
     } finally {
         if (admin != null) {
             try {
                 // Close the Admin object.
                 admin.close();
             } catch (IOException e) {
                 LOG.error("Failed to close admin ", e);
             }
         }
     }
     LOG.info("Exiting testCreateTable.");
}