HMerge (Apache HBase 1.2.12 API)

java.lang.Object
- org.apache.hadoop.hbase.util.HMerge

```
@InterfaceAudience.Private
 class HMerge
extends Object
```
A non-instantiable class that has a static method capable of compacting a table by merging adjacent regions.

Nested Class Summary

Nested Classes
Modifier and Type Class and Description

private static class HMerge.Merger

private static class HMerge.OnlineMerger
Instantiated to compact a normal user table

Nested Classes
Modifier and Type	Class and Description
`private static class`	`HMerge.Merger`
`private static class`	`HMerge.OnlineMerger` Instantiated to compact a normal user table

Field Summary

Fields
Modifier and Type Field and Description

private static org.apache.commons.logging.Log LOG

(package private) static Random rand

Fields
Modifier and Type	Field and Description
`private static org.apache.commons.logging.Log`	`LOG`
`(package private) static Random`	`rand`

Constructor Summary

Constructors
Modifier Constructor and Description

private HMerge()

Constructors
Modifier	Constructor and Description
`private`	`HMerge()`

Method Summary

Methods
Modifier and Type	Method and Description
`static void`	`merge(org.apache.hadoop.conf.Configuration conf, org.apache.hadoop.fs.FileSystem fs, TableName tableName)` Scans the table and merges two adjacent regions if they are small.
`static void`	`merge(org.apache.hadoop.conf.Configuration conf, org.apache.hadoop.fs.FileSystem fs, TableName tableName, boolean testMasterRunning)` Scans the table and merges two adjacent regions if they are small.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - LOG
```
private static final org.apache.commons.logging.Log LOG
```
  - rand
```
static final Random rand
```
- Constructor Detail
  - HMerge
```
private HMerge()
```
- Method Detail
  - merge
```
public static void merge(org.apache.hadoop.conf.Configuration conf,
         org.apache.hadoop.fs.FileSystem fs,
         TableName tableName)
                  throws IOException
```
    Scans the table and merges two adjacent regions if they are small. This only happens when a lot of rows are deleted. When merging the hbase:meta region, the HBase instance must be offline. When merging a normal table, the HBase instance must be online, but the table must be disabled.
    
    Parameters:
    conf - - configuration object for HBase
    fs - - FileSystem where regions reside
    tableName - - Table to be compacted
    
    Throws:
    
    IOException
  - merge
```
public static void merge(org.apache.hadoop.conf.Configuration conf,
         org.apache.hadoop.fs.FileSystem fs,
         TableName tableName,
         boolean testMasterRunning)
                  throws IOException
```
    Scans the table and merges two adjacent regions if they are small. This only happens when a lot of rows are deleted. When merging the hbase:meta region, the HBase instance must be offline. When merging a normal table, the HBase instance must be online, but the table must be disabled.
    
    Parameters:
    conf - - configuration object for HBase
    fs - - FileSystem where regions reside
    tableName - - Table to be compacted
    testMasterRunning - True if we are to verify master is down before running merge
    
    Throws:
    
    IOException

Class HMerge

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

LOG

rand

Constructor Detail

HMerge

Method Detail

merge

merge