BloomFilter

java.lang.Object
- org.apache.kudu.util.BloomFilter

```
@InterfaceAudience.Public
 @InterfaceStability.Unstable
 @NotThreadSafe
public class BloomFilter
extends Object
```
An space-efficient filter which offers an approximate containment check.
It can be used to filter all the records which are wanted, but doesn't guarantee to filter out all the records which are not wanted.
Please check this wiki for more details.
The BloomFilter here is a scanning filter and used to constrain the number of records returned from TServer. It provides different types of put methods. When you put a record into BloomFilter, it means you expect the TServer to return records with the same value in a scan.
Here is an example for use:
```
 
   BloomFilter bf = BloomFilter.BySizeAndFPRate(numBytes);
   bf.put(1);
   bf.put(3);
   bf.put(4);
   byte[] bitSet = bf.getBitSet();
   byte[] numHashes = bf.getNumHashes();
   String hashFunctionName = bf.getHashFunctionName();
   // TODO: implement the interface for serializing and sending
   // (bitSet, numHashes, hashFunctionName) to TServer.
 
 
```

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`static BloomFilter`	`byCount(int expectedCount)` Generate bloom filter, default hashing is `Murmur2` and false positive rate is 0.01.
`static BloomFilter`	`byCountAndFPRate(int expectedCount, double fpRate)` Generate bloom filter, default hashing is `Murmur2`.
`static BloomFilter`	`byCountAndFPRate(int expectedCount, double fpRate, org.apache.kudu.util.BloomFilter.HashFunction hashFunction)` Generate bloom filter.
`static BloomFilter`	`bySize(int numBytes)` Generate bloom filter, default hashing is `Murmur2` and false positive rate is 0.01.
`static BloomFilter`	`bySizeAndFPRate(int numBytes, double fpRate)` Generate bloom filter, default hashing is `Murmur2`.
`static BloomFilter`	`bySizeAndFPRate(int numBytes, double fpRate, org.apache.kudu.util.BloomFilter.HashFunction hashFunction)` Generate bloom filter.
`byte[]`	`getBitSet()` Get the internal bit set in bytes.
`String`	`getHashFunctionName()` Get the name of hashing used when updating or checking containment.
`int`	`getNumHashes()` Get the number of hashing times when updating or checking containment.
`void`	`put(boolean data)` Update bloom filter with a `boolean`.
`void`	`put(byte data)` Update bloom filter with a `byte`.
`void`	`put(byte[] data)` Update bloom filter with a `byte[]`.
`void`	`put(double data)` Update bloom filter with a `double`.
`void`	`put(float data)` Update bloom filter with a `float`.
`void`	`put(int data)` Update bloom filter with a `int`.
`void`	`put(long data)` Update bloom filter with a `long`.
`void`	`put(short data)` Update bloom filter with a `short`.
`void`	`put(String data)` Update bloom filter with a `String`.
`String`	`toString()`

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

- Method Detail
  - bySize
```
public static BloomFilter bySize(int numBytes)
```
    Generate bloom filter, default hashing is Murmur2 and false positive rate is 0.01.
    
    Parameters:
    
    numBytes - size of bloom filter in bytes
  - bySizeAndFPRate
```
public static BloomFilter bySizeAndFPRate(int numBytes,
                                          double fpRate)
```
    Generate bloom filter, default hashing is Murmur2.
    
    Parameters:
    
    numBytes - size of bloom filter in bytes
    
    fpRate - the probability that TServer will erroneously return a record that has not ever been put into the BloomFilter.
  - bySizeAndFPRate
```
public static BloomFilter bySizeAndFPRate(int numBytes,
                                          double fpRate,
                                          org.apache.kudu.util.BloomFilter.HashFunction hashFunction)
```
    Generate bloom filter.
    
    Parameters:
    
    numBytes - size of bloom filter in bytes
    
    fpRate - the probability that TServer will erroneously return a record that has not ever been put into the BloomFilter.
    
    hashFunction - hashing used when updating or checking containment, user should pick the hashing function from HashFunctions
  - byCount
```
public static BloomFilter byCount(int expectedCount)
```
    Generate bloom filter, default hashing is Murmur2 and false positive rate is 0.01.
    
    Parameters:
    
    expectedCount - The expected number of elements, targeted by this bloom filter. It is used to size the bloom filter.
  - byCountAndFPRate
```
public static BloomFilter byCountAndFPRate(int expectedCount,
                                           double fpRate)
```
    Generate bloom filter, default hashing is Murmur2.
    
    Parameters:
    
    expectedCount - The expected number of elements, targeted by this bloom filter. It is used to size the bloom filter.
    
    fpRate - the probability that TServer will erroneously return a record that has not ever been put into the BloomFilter.
  - byCountAndFPRate
```
public static BloomFilter byCountAndFPRate(int expectedCount,
                                           double fpRate,
                                           org.apache.kudu.util.BloomFilter.HashFunction hashFunction)
```
    Generate bloom filter.
    
    Parameters:
    
    expectedCount - The expected number of elements, targeted by this bloom filter. It is used to size the bloom filter.
    
    fpRate - the probability that TServer will erroneously return a record that has not ever been put into the BloomFilter.
    
    hashFunction - hashing used when updating or checking containment, user should pick the hashing function from HashFunctions
  - put
```
public void put(byte[] data)
```
    Update bloom filter with a byte[].
  - put
```
public void put(boolean data)
```
    Update bloom filter with a boolean.
  - put
```
public void put(byte data)
```
    Update bloom filter with a byte.
  - put
```
public void put(short data)
```
    Update bloom filter with a short.
  - put
```
public void put(int data)
```
    Update bloom filter with a int.
  - put
```
public void put(long data)
```
    Update bloom filter with a long.
  - put
```
public void put(float data)
```
    Update bloom filter with a float.
  - put
```
public void put(double data)
```
    Update bloom filter with a double.
  - put
```
public void put(String data)
```
    Update bloom filter with a String.
  - getBitSet
```
public byte[] getBitSet()
```
    Get the internal bit set in bytes.
  - getNumHashes
```
public int getNumHashes()
```
    Get the number of hashing times when updating or checking containment.
  - getHashFunctionName
```
public String getHashFunctionName()
```
    Get the name of hashing used when updating or checking containment.
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class Object

Class BloomFilter

Method Summary

Methods inherited from class java.lang.Object

Method Detail

bySize

bySizeAndFPRate

bySizeAndFPRate

byCount

byCountAndFPRate

byCountAndFPRate

put

put

put

put

put

put

put

put

put

getBitSet

getNumHashes

getHashFunctionName

toString