[C++] hbase 预分区

• 首先是热点写，我们总是会往最大的start-key所在的region写东西，因为我们的rowkey总是会比之前的大，并且hbase的是按升序方式排序的。所以写操作总是被定位到无上界的那个region中。
  
• 其次，由于写热点，我们总是往最大start-key的region写记录，之前分裂出来的region不会再被写数据，有点被打进冷宫的赶脚，它们都处于半满状态，这样的分布也是不利的。
  
• 如果在写比较频率的场景下，数据增长快，split的次数也会增多，由于split是比较耗时耗资源的，所以我们并不希望这种事情经常发生。
  

/**
 * @ Author: keguang
 * @ Date: 2018/11/17 14:13
 * @ version: v1.0.0
 * @ description:
 */
public class RowKeyAction {
  /**
   * 生成user_label预分区的startkey, endkey
   * @return
   */
  public static byte[][] getSplitKeys() {
    String end = "|";
    String[] keys = new String[]{"{0", "{1", "{2", "{3", "{4", "{5",
        "{6", "{7", "{8", "{9", "{A", "{B", "{C", "{D", "{E", "{F"
    };
    byte[][] splitKeys = new byte[keys.length][];
    TreeSet<byte[]> rows = new TreeSet<byte[]>(Bytes.BYTES_COMPARATOR);//升序排序
    for (int i = 0; i < keys.length; i++) {
      rows.add(Bytes.toBytes(keys[i] + end));
    }
    Iterator<byte[]> rowKeyIter = rows.iterator();
    int i = 0;
    while (rowKeyIter.hasNext()) {
      byte[] tempRow = rowKeyIter.next();
      rowKeyIter.remove();
      splitKeys[i] = tempRow;
      i++;
    }
    return splitKeys;
  }
  public static byte[][] getSplitKeys2() {
    String end = "|";
    String[] keys0 = new String[]{"{0", "{1", "{2", "{3", "{4", "{5",
        "{6", "{7", "{8", "{9", "{A", "{B", "{C", "{D", "{E", "{F"
    };
    String[] keys00 = new String[]{"3", "7", "B", "F"};
    String[] keys = new String[64];

    List<String> list = new ArrayList<>();
    for(int i = 0;i < keys0.length;i++){
      for(int j = 0;j < keys00.length;j++){
        list.add(keys0[i] + keys00[j]);
      }
    }
    int cnt = 0;
    for(String key: list){
      keys[cnt] = key;
      cnt = cnt + 1;
    }
    byte[][] splitKeys = new byte[keys.length][];
    TreeSet<byte[]> rows = new TreeSet<byte[]>(Bytes.BYTES_COMPARATOR);//升序排序
    for (int i = 0; i < keys.length; i++) {
      rows.add(Bytes.toBytes(keys[i] + end));
    }
    Iterator<byte[]> rowKeyIter = rows.iterator();
    int i = 0;
    while (rowKeyIter.hasNext()) {
      byte[] tempRow = rowKeyIter.next();
      rowKeyIter.remove();
      splitKeys[i] = tempRow;
      i++;
    }
    return splitKeys;
  }
}
/**
 * @version v1.0.0
 * @Author:keguang
 * @Date:2018/9/5 11:15
 */
public class Demo{
  // 新建 hbase 表
  @Test
  public void test4(){
    String tbName = "hm2:flash_people";
    HbaseUtil.initConnection();
    List<String> family = new ArrayList<>();
    family.add("info");
    // 生成rowkeys预分区
    byte[][] splitKeys = RowKeyAction.getSplitKeys();
    boolean result = HbaseUtil.createTableBySplitKeys(tbName, family, splitKeys);
    if(result){
      System.out.println(tbName + " 建表成功...");
    }
  }
}