1. HBase query method
The query implementation of hbase only provides two ways:
- Get a unique record by the specified rowkey: get method.
- Get a batch of records according to specified conditions: scan method.
The scan method is used to implement the conditional query function. When using scan, pay attention to the following values:
- The speed of scan can be improved by the setCaching and setBatch methods (space for time)
- scan can be limited by setStartRow and setEndRow. The smaller the range, the higher the performance.
- Scan can add filters through the setFilter method, which is also the basis for paging and multi-condition queries.
Second, the use of RowFilter
| operator | description |
| less |
less than |
| less_or_equal |
less than or equal to |
| equal | equal |
| not_equal | not equal to |
| greater_or_equal | greater or equal to |
| greater | more than the |
| no_op | exclude all |
| Comparator | description |
| BinaryComparator | Compare using bytes.comparaTo() |
| BinaryPrefixComparator | Similar to BinaryComparator, start comparing from the front |
| NullComparator | |
| BitComparator | |
| RegexStringComparator | regular expression |
| subStringComparator | Treat numbers as strings and use contains() to judge |
import java.io.IOException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.HBaseConfiguration;
import org.apache.hadoop.hbase.HColumnDescriptor;
import org.apache.hadoop.hbase.HTableDescriptor;
import org.apache.hadoop.hbase.client.HBaseAdmin;
import org.apache.hadoop.hbase.client.HTable;
import org.apache.hadoop.hbase.client.Put;
import org.apache.hadoop.hbase.client.Result;
import org.apache.hadoop.hbase.client.ResultScanner;
import org.apache.hadoop.hbase.client.Scan;
import org.apache.hadoop.hbase.filter.BinaryComparator;
import org.apache.hadoop.hbase.filter.BinaryPrefixComparator;
import org.apache.hadoop.hbase.filter.CompareFilter;
import org.apache.hadoop.hbase.filter.Filter;
import org.apache.hadoop.hbase.filter.RegexStringComparator;
import org.apache.hadoop.hbase.filter.RowFilter;
import org.apache.hadoop.hbase.filter.SubstringComparator;
public class TestHbaseRowFilter {
String tableName = "test_row_filter";
Configuration config = HBaseConfiguration.create();
/**
* Part of the code comes from the hbase authoritative guide
* @throws IOException
*/
public void testRowFilter() throws IOException {
HTable table = new HTable(config, tableName);
Scan scan = new Scan();
System.out.println("Row less than or equal to row010");
Filter filter1 = new RowFilter(CompareFilter.CompareOp.LESS_OR_EQUAL,
new BinaryComparator("row010".getBytes()));
scan.setFilter(filter1);
ResultScanner scanner1 = table.getScanner(scan);
for (Result res : scanner1) {
System.out.println(res);
}
scanner1.close();
System.out.println("Regularly get the line ending with 5");
Filter filter2 = new RowFilter(CompareFilter.CompareOp.EQUAL,
new RegexStringComparator(".*5[ DISCUZ_CODE_0 ]quot;));
scan.setFilter(filter2);
ResultScanner scanner2 = table.getScanner(scan);
for (Result res : scanner2) {
System.out.println(res);
}
scanner2.close();
System.out.println("Line containing 5");
Filter filter3 = new RowFilter(CompareFilter.CompareOp.EQUAL,
new SubstringComparator("5"));
scan.setFilter(filter3);
ResultScanner scanner3 = table.getScanner(scan);
for (Result res : scanner3) {
System.out.println(res);
}
scanner3.close();
System.out.println("The beginning is row01");
Filter filter4 = new RowFilter(CompareFilter.CompareOp.EQUAL,
new BinaryPrefixComparator("row01".getBytes()));
scan.setFilter(filter4);
ResultScanner scanner4 = table.getScanner(scan);
for (Result res : scanner4) {
System.out.println(res);
}
scanner3.close();
}
/**
* Initialization data
*/
public void init() {
// create table and initialize data
try {
HBaseAdmin admin = new HBaseAdmin(config);
if (!admin.tableExists(tableName)) {
HTableDescriptor htd = new HTableDescriptor(tableName);
HColumnDescriptor hcd1 = new HColumnDescriptor("data");
htd.addFamily (hcd1);
HColumnDescriptor hcd2 = new HColumnDescriptor("url");
htd.addFamily (hcd2);
admin.createTable(htd);
}
HTable table = new HTable(config, tableName);
table.setAutoFlush(false);
int count = 50;
for (int i = 1; i <= count; ++i) {
Put p = new Put(String.format("row%03d", i).getBytes());
p.add("data".getBytes(), String.format("col%01d", i % 10)
.getBytes(), String.format("data%03d", i).getBytes());
p.add("url".getBytes(), String.format("col%01d", i % 10)
.getBytes(), String.format("url%03d", i).getBytes());
table.put(p);
}
table.close();
} catch (IOException e) {
e.printStackTrace ();
}
}
/**
* @param args
* @throws IOException
*/
public static void main(String[] args) throws IOException {
TestHbaseRowFilter test = new TestHbaseRowFilter();
test.init();
test.testRowFilter();
}
}
Rows less than or equal to row010
keyvalues = {row001 / data: col1 / 1364133382268 / Put / vlen = 7, row001 / url: col1 / 1364133382268 / Put / vlen = 6}
keyvalues = {row002 / data: col2 / 1364133382268 / Put / vlen = 7, row002 / url: col2 / 1364133382268 / Put / vlen = 6}
keyvalues = {row003 / data: col3 / 1364133382268 / Put / vlen = 7, row003 / url: col3 / 1364133382268 / Put / vlen = 6}
keyvalues = {row004 / data: col4 / 1364133382268 / Put / vlen = 7, row004 / url: col4 / 1364133382268 / Put / vlen = 6}
keyvalues = {row005 / data: col5 / 1364133382268 / Put / vlen = 7, row005 / url: col5 / 1364133382268 / Put / vlen = 6}
keyvalues = {row006 / data: col6 / 1364133382268 / Put / vlen = 7, row006 / url: col6 / 1364133382268 / Put / vlen = 6}
keyvalues = {row007 / data: col7 / 1364133382268 / Put / vlen = 7, row007 / url: col7 / 1364133382268 / Put / vlen = 6}
keyvalues = {row008 / data: col8 / 1364133382268 / Put / vlen = 7, row008 / url: col8 / 1364133382268 / Put / vlen = 6}
keyvalues = {row009 / data: col9 / 1364133382268 / Put / vlen = 7, row009 / url: col9 / 1364133382268 / Put / vlen = 6}
keyvalues = {row010 / data: col0 / 1364133382268 / Put / vlen = 7, row010 / url: col0 / 1364133382268 / Put / vlen = 6}
regex to get lines ending with 5
keyvalues = {row005 / data: col5 / 1364133382268 / Put / vlen = 7, row005 / url: col5 / 1364133382268 / Put / vlen = 6}
keyvalues = {row015 / data: col5 / 1364133382268 / Put / vlen = 7, row015 / url: col5 / 1364133382268 / Put / vlen = 6}
keyvalues = {row025 / data: col5 / 1364133382268 / Put / vlen = 7, row025 / url: col5 / 1364133382268 / Put / vlen = 6}
keyvalues = {row035 / data: col5 / 1364133382268 / Put / vlen = 7, row035 / url: col5 / 1364133382268 / Put / vlen = 6}
keyvalues = {row045 / data: col5 / 1364133382268 / Put / vlen = 7, row045 / url: col5 / 1364133382268 / Put / vlen = 6}
The package line has 5 lines
keyvalues = {row005 / data: col5 / 1364133382268 / Put / vlen = 7, row005 / url: col5 / 1364133382268 / Put / vlen = 6}
keyvalues = {row015 / data: col5 / 1364133382268 / Put / vlen = 7, row015 / url: col5 / 1364133382268 / Put / vlen = 6}
keyvalues = {row025 / data: col5 / 1364133382268 / Put / vlen = 7, row025 / url: col5 / 1364133382268 / Put / vlen = 6}
keyvalues = {row035 / data: col5 / 1364133382268 / Put / vlen = 7, row035 / url: col5 / 1364133382268 / Put / vlen = 6}
keyvalues = {row045 / data: col5 / 1364133382268 / Put / vlen = 7, row045 / url: col5 / 1364133382268 / Put / vlen = 6}
keyvalues = {row050 / data: col0 / 1364133382268 / Put / vlen = 7, row050 / url: col0 / 1364133382268 / Put / vlen = 6}
Beginning with row01
keyvalues = {row010 / data: col0 / 1364133382268 / Put / vlen = 7, row010 / url: col0 / 1364133382268 / Put / vlen = 6}
keyvalues = {row011 / data: col1 / 1364133382268 / Put / vlen = 7, row011 / url: col1 / 1364133382268 / Put / vlen = 6}
keyvalues = {row012 / data: col2 / 1364133382268 / Put / vlen = 7, row012 / url: col2 / 1364133382268 / Put / vlen = 6}
keyvalues = {row013 / data: col3 / 1364133382268 / Put / vlen = 7, row013 / url: col3 / 1364133382268 / Put / vlen = 6}
keyvalues = {row014 / data: col4 / 1364133382268 / Put / vlen = 7, row014 / url: col4 / 1364133382268 / Put / vlen = 6}
keyvalues = {row015 / data: col5 / 1364133382268 / Put / vlen = 7, row015 / url: col5 / 1364133382268 / Put / vlen = 6}
keyvalues = {row016 / data: col6 / 1364133382268 / Put / vlen = 7, row016 / url: col6 / 1364133382268 / Put / vlen = 6}
keyvalues = {row017 / data: col7 / 1364133382268 / Put / vlen = 7, row017 / url: col7 / 1364133382268 / Put / vlen = 6}
keyvalues = {row018 / data: col8 / 1364133382268 / Put / vlen = 7, row018 / url: col8 / 1364133382268 / Put / vlen = 6}
keyvalues = {row019 / data: col9 / 1364133382268 / Put / vlen = 7, row019 / url: col9 / 1364133382268 / Put / vlen = 6}