org.apache.drill.exec.planner.common

Class NumericEquiDepthHistogram

java.lang.Object

org.apache.drill.exec.planner.common.NumericEquiDepthHistogram

All Implemented Interfaces:

Histogram

public class NumericEquiDepthHistogram
extends Object
implements Histogram

A column specific equi-depth histogram which is meant for numeric data types

Constructor Summary

Constructors

Constructor and Description
NumericEquiDepthHistogram()
NumericEquiDepthHistogram(int numBuckets)

Method Summary

Modifier and Type	Method and Description
static NumericEquiDepthHistogram	buildFromTDigest(byte[] tdigest_array, int numBuckets, long nonNullCount) Build a Numeric Equi-Depth Histogram from a t-digest byte array
Double	estimatedSelectivity(org.apache.calcite.rex.RexNode columnFilter, long totalRowCount, long ndv) Estimate the selectivity of a filter which may contain several range predicates and in the general case is of type: col op value1 AND col op value2 AND col op value3 ...
Double[]	getBuckets()
int	getNumBuckets() Get the number of buckets in the histogram number of buckets is 1 less than the total # entries in the buckets array since last entry is the end point of the last bucket
double	getNumRowsPerBucket()
protected long	getSelectedRows(org.apache.drill.shaded.guava.com.google.common.collect.Range range, long ndv)
protected void	setBucketValue(int index, Double value)
void	setNumRowsPerBucket(double numRows)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

NumericEquiDepthHistogram

public NumericEquiDepthHistogram()

NumericEquiDepthHistogram

public NumericEquiDepthHistogram(int numBuckets)

Method Detail

getNumRowsPerBucket

public double getNumRowsPerBucket()

setNumRowsPerBucket

public void setNumRowsPerBucket(double numRows)

getBuckets

public Double[] getBuckets()

setBucketValue

protected void setBucketValue(int index,
                              Double value)

getNumBuckets

public int getNumBuckets()

Get the number of buckets in the histogram number of buckets is 1 less than the total # entries in the buckets array since last entry is the end point of the last bucket

estimatedSelectivity

public Double estimatedSelectivity(org.apache.calcite.rex.RexNode columnFilter,
                                   long totalRowCount,
                                   long ndv)

Estimate the selectivity of a filter which may contain several range predicates and in the general case is of type: col op value1 AND col op value2 AND col op value3 ...

e.g a > 10 AND a < 50 AND a >= 20 AND a <= 70 ...

Even though in most cases it will have either 1 or 2 range conditions, we still have to handle the general case For each conjunct, we will find the histogram bucket ranges and intersect them, taking into account that the first and last bucket may be partially covered and all other buckets in the middle are fully covered.

Specified by:

estimatedSelectivity in interface Histogram

Returns:

estimated selectivity or NULL if it could not be estimated for any reason

getSelectedRows

protected long getSelectedRows(org.apache.drill.shaded.guava.com.google.common.collect.Range range,
                               long ndv)

buildFromTDigest

public static NumericEquiDepthHistogram buildFromTDigest(byte[] tdigest_array,
                                                         int numBuckets,
                                                         long nonNullCount)

Build a Numeric Equi-Depth Histogram from a t-digest byte array

Parameters:

tdigest_array -

numBuckets -

nonNullCount -

Returns:

An instance of NumericEquiDepthHistogram