T - the type of the values being combinedpublic static class ApproximateQuantiles.ApproximateQuantilesCombineFn<T,ComparatorT extends java.util.Comparator<T> & java.io.Serializable> extends Combine.AccumulatingCombineFn<T,org.apache.beam.sdk.transforms.ApproximateQuantiles.QuantileState<T,ComparatorT>,java.util.List<T>>
ApproximateQuantilesCombineFn combiner gives an idea of the distribution of a
collection of values using approximate N-tiles. The output of this combiner is a List of size numQuantiles, containing the input values' minimum value, numQuantiles-2 intermediate values, and maximum value, in sorted order, so for traditional
N-tiles, one should use ApproximateQuantilesCombineFn#create(N+1).
If there are fewer values to combine than numQuantiles, then the result List
will contain all the values being combined, in sorted order.
Values are ordered using either a specified Comparator or the values' natural
ordering.
To evaluate the quantiles we use the "New Algorithm" described here:
[MRL98] Manku, Rajagopalan & Lindsay, "Approximate Medians and other Quantiles in One Pass and with Limited Memory", Proc. 1998 ACM SIGMOD, Vol 27, No 2, p 426-435, June 1998. http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.6.6513&rep=rep1&type=pdf
The default error bound is 1 / N, though in practice the accuracy tends to be much
better.
See create(int, Comparator, long, double) for more information about the meaning of
epsilon, and withEpsilon(double) for a convenient way to adjust it.
Combine.AccumulatingCombineFn.Accumulator<InputT,AccumT,OutputT>| Modifier and Type | Field and Description |
|---|---|
static long |
DEFAULT_MAX_NUM_ELEMENTS
The cost (in time and space) to compute quantiles to a given accuracy is a function of the
total number of elements in the data set.
|
| Modifier and Type | Method and Description |
|---|---|
static <T extends java.lang.Comparable<T>> |
create(int numQuantiles)
Like
create(int, Comparator), but sorts values using their natural ordering. |
static <T,ComparatorT extends java.util.Comparator<T> & java.io.Serializable> |
create(int numQuantiles,
ComparatorT compareFn)
Returns an approximate quantiles combiner with the given
compareFn and desired number
of quantiles. |
static <T,ComparatorT extends java.util.Comparator<T> & java.io.Serializable> |
create(int numQuantiles,
ComparatorT compareFn,
long maxNumElements,
double epsilon)
Creates an approximate quantiles combiner with the given
compareFn and desired number
of quantiles. |
org.apache.beam.sdk.transforms.ApproximateQuantiles.QuantileState<T,ComparatorT> |
createAccumulator()
Returns a new, mutable accumulator value, representing the accumulation of zero input values.
|
java.lang.reflect.TypeVariable<?> |
getAccumTVariable()
Returns the
TypeVariable of AccumT. |
Coder<org.apache.beam.sdk.transforms.ApproximateQuantiles.QuantileState<T,ComparatorT>> |
getAccumulatorCoder(CoderRegistry registry,
Coder<T> elementCoder)
Returns the
Coder to use for accumulator AccumT values, or null if it is not
able to be inferred. |
Coder<OutputT> |
getDefaultOutputCoder(CoderRegistry registry,
Coder<InputT> inputCoder)
Returns the
Coder to use by default for output OutputT values, or null if it
is not able to be inferred. |
java.lang.String |
getIncompatibleGlobalWindowErrorMessage()
Returns the error message for not supported default values in Combine.globally().
|
java.lang.reflect.TypeVariable<?> |
getInputTVariable()
Returns the
TypeVariable of InputT. |
java.lang.reflect.TypeVariable<?> |
getOutputTVariable()
Returns the
TypeVariable of OutputT. |
void |
populateDisplayData(DisplayData.Builder builder)
Register display data for the given transform or component.
|
ApproximateQuantiles.ApproximateQuantilesCombineFn<T,ComparatorT> |
withEpsilon(double epsilon)
Returns an
ApproximateQuantilesCombineFn that's like this one except that it uses the
specified epsilon value. |
ApproximateQuantiles.ApproximateQuantilesCombineFn<T,ComparatorT> |
withMaxInputSize(long maxNumElements)
Returns an
ApproximateQuantilesCombineFn that's like this one except that it uses the
specified maxNumElements value. |
addInput, extractOutput, mergeAccumulatorsapply, compact, defaultValue, getOutputTypepublic static final long DEFAULT_MAX_NUM_ELEMENTS
public static <T,ComparatorT extends java.util.Comparator<T> & java.io.Serializable> ApproximateQuantiles.ApproximateQuantilesCombineFn<T,ComparatorT> create(int numQuantiles, ComparatorT compareFn)
compareFn and desired number
of quantiles. A total of numQuantiles elements will appear in the output list,
including the minimum and maximum.
The Comparator must be Serializable.
The default error bound is 1 / numQuantiles, which holds as long as the number of
elements is less than DEFAULT_MAX_NUM_ELEMENTS.
public static <T extends java.lang.Comparable<T>> ApproximateQuantiles.ApproximateQuantilesCombineFn<T,Top.Natural<T>> create(int numQuantiles)
create(int, Comparator), but sorts values using their natural ordering.public ApproximateQuantiles.ApproximateQuantilesCombineFn<T,ComparatorT> withEpsilon(double epsilon)
ApproximateQuantilesCombineFn that's like this one except that it uses the
specified epsilon value. Does not modify this combiner.
See create(int, Comparator, long, double) for more information about the meaning
of epsilon.
public ApproximateQuantiles.ApproximateQuantilesCombineFn<T,ComparatorT> withMaxInputSize(long maxNumElements)
ApproximateQuantilesCombineFn that's like this one except that it uses the
specified maxNumElements value. Does not modify this combiner.
See create(int, Comparator, long, double) for more information about the meaning
of maxNumElements.
public static <T,ComparatorT extends java.util.Comparator<T> & java.io.Serializable> ApproximateQuantiles.ApproximateQuantilesCombineFn<T,ComparatorT> create(int numQuantiles, ComparatorT compareFn, long maxNumElements, double epsilon)
compareFn and desired number
of quantiles. A total of numQuantiles elements will appear in the output list,
including the minimum and maximum.
The Comparator must be Serializable.
The default error bound is epsilon, which holds as long as the number of elements
is less than maxNumElements. Specifically, if one considers the input as a sorted
list x_1, ..., x_N, then the distance between the each exact quantile x_c and its
approximation x_c' is bounded by |c - c'| < epsilon * N. Note that these errors are
worst-case scenarios; in practice the accuracy tends to be much better.
public org.apache.beam.sdk.transforms.ApproximateQuantiles.QuantileState<T,ComparatorT> createAccumulator()
Combine.CombineFncreateAccumulator in class Combine.CombineFn<T,org.apache.beam.sdk.transforms.ApproximateQuantiles.QuantileState<T,ComparatorT extends java.util.Comparator<T> & java.io.Serializable>,java.util.List<T>>public Coder<org.apache.beam.sdk.transforms.ApproximateQuantiles.QuantileState<T,ComparatorT>> getAccumulatorCoder(CoderRegistry registry, Coder<T> elementCoder)
CombineFnBase.GlobalCombineFnCoder to use for accumulator AccumT values, or null if it is not
able to be inferred.
By default, uses the knowledge of the Coder being used for InputT values
and the enclosing Pipeline's CoderRegistry to try to infer the Coder for
AccumT values.
This is the Coder used to send data through a communication-intensive shuffle step, so a compact and efficient representation may have significant performance benefits.
getAccumulatorCoder in interface CombineFnBase.GlobalCombineFn<T,org.apache.beam.sdk.transforms.ApproximateQuantiles.QuantileState<T,ComparatorT extends java.util.Comparator<T> & java.io.Serializable>,java.util.List<T>>public void populateDisplayData(DisplayData.Builder builder)
populateDisplayData(DisplayData.Builder) is invoked by Pipeline runners to collect
display data via DisplayData.from(HasDisplayData). Implementations may call super.populateDisplayData(builder) in order to register display data in the current namespace,
but should otherwise use subcomponent.populateDisplayData(builder) to use the namespace
of the subcomponent.
By default, does not register any display data. Implementors may override this method to provide their own display data.
populateDisplayData in interface HasDisplayDatabuilder - The builder to populate with display data.HasDisplayDatapublic Coder<OutputT> getDefaultOutputCoder(CoderRegistry registry, Coder<InputT> inputCoder) throws CannotProvideCoderException
CombineFnBase.GlobalCombineFnCoder to use by default for output OutputT values, or null if it
is not able to be inferred.
By default, uses the knowledge of the Coder being used for input InputT
values and the enclosing Pipeline's CoderRegistry to try to infer the Coder
for OutputT values.
getDefaultOutputCoder in interface CombineFnBase.GlobalCombineFn<InputT,AccumT,OutputT>CannotProvideCoderExceptionpublic java.lang.String getIncompatibleGlobalWindowErrorMessage()
CombineFnBase.GlobalCombineFngetIncompatibleGlobalWindowErrorMessage in interface CombineFnBase.GlobalCombineFn<InputT,AccumT,OutputT>public java.lang.reflect.TypeVariable<?> getInputTVariable()
TypeVariable of InputT.public java.lang.reflect.TypeVariable<?> getAccumTVariable()
TypeVariable of AccumT.public java.lang.reflect.TypeVariable<?> getOutputTVariable()
TypeVariable of OutputT.