Creating a Table

Function Description

HBase allows you to create a table using the createTable method of the org.apache.hadoop.hbase.client.Admin object. You need to specify a table name and a column family name. You can create a table by using either of the following methods, but the latter one is recommended.

• Quickly create a table. A newly created table contains only one region, which will be automatically split into multiple new regions as data increases.
• Create a table using pre-assigned regions. You can pre-assign multiple regions before creating a table. This mode accelerates data write at the beginning of massive data write.

The column name and column family name of a table consist of letters, digits, and underscores (_) but cannot contain any special characters.

Sample Code

The following code snippets are in the testCreateTable method in the HBaseExample class of the com.huawei.bigdata.hbase.examples packet.

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.");
}