How to read incremental data from HBase?

2 years ago
Liam
2 minutes

There are two methods you can use to read incremental data from HBase.

  1. Create a connection object for HBase and specify the table name and column family to be read.
  2. Use the Scan object to set the scanning range and filter conditions in order to only retrieve incremental data.
  3. Get a ResultScanner object by using the getScanner method of the Table object.
  4. Iterate through the ResultScanner object, using the Result object to retrieve the data from each row.

Here is an example code snippet demonstrating how to perform incremental reading using the Java API of HBase.

Configuration config = HBaseConfiguration.create();
Connection connection = ConnectionFactory.createConnection(config);
TableName tableName = TableName.valueOf("your_table_name");
Table table = connection.getTable(tableName);

Scan scan = new Scan();
scan.setStartRow(Bytes.toBytes("start_row_key"));
scan.setStopRow(Bytes.toBytes("stop_row_key"));

ResultScanner scanner = table.getScanner(scan);
for (Result result : scanner) {
    // 处理每一行的数据
    for (Cell cell : result.rawCells()) {
        // 处理每一个单元格的数据
        byte[] row = CellUtil.cloneRow(cell);
        byte[] family = CellUtil.cloneFamily(cell);
        byte[] qualifier = CellUtil.cloneQualifier(cell);
        byte[] value = CellUtil.cloneValue(cell);
        // 处理数据
    }
}

scanner.close();
table.close();
connection.close();
  1. Create an HBase connection object and specify the table name and column family to read from.
  2. Use the TableMapReduceUtil class to create a Job object and configure its input and output formats.
  3. Set the scanning range and filter conditions using the Scan object to only retrieve incremental data.
  4. Use the initTableMapperJob method of the TableMapReduceUtil class to configure the Mapper class, input table name, and Scan object.
  5. Use the `initTableReducerJob` method of the `TableMapReduceUtil` class to specify the Reducer class, output table name, and connection object.
  6. Execute the Job object.

Here is a code snippet demonstrating how to use HBase’s MapReduce for incremental reading.

Configuration config = HBaseConfiguration.create();
Connection connection = ConnectionFactory.createConnection(config);
TableName inputTableName = TableName.valueOf("your_input_table_name");
TableName outputTableName = TableName.valueOf("your_output_table_name");

Scan scan = new Scan();
scan.setStartRow(Bytes.toBytes("start_row_key"));
scan.setStopRow(Bytes.toBytes("stop_row_key"));

Job job = Job.getInstance(config);
job.setJarByClass(IncrementalRead.class);
job.setMapperClass(IncrementalReadMapper.class);
job.setReducerClass(IncrementalReadReducer.class);
job.setInputFormatClass(TableInputFormat.class);
job.setOutputFormatClass(TableOutputFormat.class);
TableMapReduceUtil.initTableMapperJob(inputTableName, scan, IncrementalReadMapper.class, ImmutableBytesWritable.class, Put.class, job);
TableMapReduceUtil.initTableReducerJob(outputTableName.getNameAsString(), IncrementalReadReducer.class, job);

job.waitForCompletion(true);

connection.close();

Please note that the sample code above is just a simple example, you will need to adjust and expand it according to your specific needs.

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