HashUtil (presto-main 345 API)

java.lang.Object
- io.prestosql.operator.aggregation.histogram.HashUtil

public final class HashUtil
extends Object

Method Summary

All Methods Static Methods Concrete Methods
Modifier and Type	Method	Description
`static int`	`calculateMaxFill(int bucketCount, float fillRatio)`
`static int`	`computeBucketCount(int expectedSize, float fillRatio)`	uses HashCommon.arraySize() which does this calculation.
`static int`	`nextBucketId(int bucketId, int mask, int probe)`
`static int`	`nextProbeLinear(int probeCount)`
`static int`	`nextSumOfCount(int probeCount)`
`static int`	`nextSumOfSquares(int probeCount)`

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

- Method Detail
  - nextProbeLinear
```
public static int nextProbeLinear(int probeCount)
```
  - nextSumOfCount
```
public static int nextSumOfCount(int probeCount)
```
  - nextSumOfSquares
```
public static int nextSumOfSquares(int probeCount)
```
  - nextBucketId
```
public static int nextBucketId(int bucketId,
                               int mask,
                               int probe)
```
    Parameters:
    
    bucketId - - previous bucketId location
    
    mask - - mask being used (typically # of buckets-1; due to power-of-2 sized bucket arrays, handles wrap-around
    
    probe - - how many buckets to jump to find next bucket
    
    Returns:
    
    next bucketId, including any necessary wrap-around (again mask handles this)
  - calculateMaxFill
```
public static int calculateMaxFill(int bucketCount,
                                   float fillRatio)
```
  - computeBucketCount
```
public static int computeBucketCount(int expectedSize,
                                     float fillRatio)
```
    uses HashCommon.arraySize() which does this calculation. this is just a wrapper to name the use of this case
    
    Parameters:
    
    expectedSize - - expected number of elements to store in the hash
    
    fillRatio - - expected fill ratio of buckets by elemements
    
    Returns:
    
    nextPowerOfTwo(expectedSize / fillRatio)