AbstractHashSampler (Apache Accumulo Core 2.0.0 API)

java.lang.Object
- org.apache.accumulo.core.client.sample.AbstractHashSampler

All Implemented Interfaces:

Sampler

Direct Known Subclasses:

RowColumnSampler, RowSampler
```
public abstract class AbstractHashSampler
extends Object
implements Sampler
```
A base class that can be used to create Samplers based on hashing. This class offers consistent options for configuring the hash function. The subclass decides which parts of the key to hash.
This class support two options passed into init(SamplerConfiguration). One option is hasher which specifies a hashing algorithm. Valid values for this option are md5, sha1, and murmur3_32. If you are not sure, then choose murmur3_32.
The second option is modulus which can have any positive integer as a value.
Any data where hash(data) % modulus == 0 will be selected for the sample.

Since:

1.8.0

Constructor Summary

Constructors
Constructor Description

AbstractHashSampler()

Method Summary

All Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method	Description
`boolean`	`accept(Key k)`
`protected abstract void`	`hash(DataOutput hasher, Key k)`	Subclass must override this method and hash some portion of the key.
`void`	`init(SamplerConfiguration config)`	Subclasses with options should override this method and call `super.init(config)`.
`protected boolean`	`isValidOption(String option)`	Subclasses with options should override this method and return true if the option is valid for the subclass or if `super.isValidOption(opt)` returns true.

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

- Constructor Detail
  - AbstractHashSampler
```
public AbstractHashSampler()
```
- Method Detail
  - isValidOption
```
protected boolean isValidOption(String option)
```
    Subclasses with options should override this method and return true if the option is valid for the subclass or if super.isValidOption(opt) returns true.
  - init
```
public void init(SamplerConfiguration config)
```
    Subclasses with options should override this method and call super.init(config).
    
    Specified by:
    
    init in interface Sampler
    
    Parameters:
    
    config - Configuration options for a sampler.
  - hash
```
protected abstract void hash(DataOutput hasher,
                             Key k)
                      throws IOException
```
    Subclass must override this method and hash some portion of the key.
    
    Parameters:
    
    hasher - Data written to this will be used to compute the hash for the key.
    
    Throws:
    
    IOException
  - accept
```
public boolean accept(Key k)
```
    Specified by:
    
    accept in interface Sampler
    
    Parameters:
    
    k - A key that was written to a rfile.
    
    Returns:
    
    True if the key (and its associated value) should be stored in the rfile's sample. Return false if it should not be included.