com.datadoghq.sketch.ddsketch.encoding

Class Flag

java.lang.Object

com.datadoghq.sketch.ddsketch.encoding.Flag

public final class Flag
extends java.lang.Object

An encoded DDSketch comprises multiple contiguous blocks (sequences of bytes). Each block is prefixed with a flag that indicates what the block contains and how the data is encoded in the block.

A flag is a encoded with a single byte, which itself contains two parts:

• the flag type (the 2 least significant bits),
• the subflag (the 6 most significant bits).

There are four flag types, for:

• the sketch features,
• the index mapping,
• the positive value store,
• the negative value store.

The meaning of the subflag depends on the flag type:

• for the sketch feature flag type, it indicates what feature is encoded,
• for the index mapping flag type, it indicates what mapping is encoded and how,
• for the store flag types, it indicates how bins are encoded.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Flag.Type

Field Summary

Fields

Modifier and Type	Field and Description
static Flag	COUNT Encodes the total count.
static Flag	MAX Encodes the global maximum value.
static Flag	MIN Encodes the global minimum value.
static Flag	SUM Encodes the total sum.
static Flag	ZERO_COUNT Encodes the count of the zero bin.

Method Summary

Modifier and Type	Method and Description
static Flag	decode(Input input) Return a flag built from the data read from the provided Input.
void	encode(Output output)
boolean	equals(java.lang.Object o)
int	hashCode()
Flag.Type	type()

Methods inherited from class java.lang.Object

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

Field Detail

ZERO_COUNT

public static final Flag ZERO_COUNT

Encodes the count of the zero bin.

Encoding format:

• [byte] flag
• [varfloat64] count of the zero bin

COUNT

public static final Flag COUNT

Encodes the total count.

Encoding format:

• [byte] flag
• [varfloat64] total count

SUM

public static final Flag SUM

Encodes the total sum.

Encoding format:

• [byte] flag
• [float64LE] total sum

MIN

public static final Flag MIN

Encodes the global minimum value.

Encoding format:

• [byte] flag
• [float64LE] global minimum value

MAX

public static final Flag MAX

Encodes the global maximum value.

Encoding format:

• [byte] flag
• [float64LE] global maximum value

Method Detail

type

public Flag.Type type()

encode

public void encode(Output output)
            throws java.io.IOException

Throws:

java.io.IOException

decode

public static Flag decode(Input input)
                   throws java.io.IOException

Return a flag built from the data read from the provided Input.

Note that for performance reasons, there is no validation happening in this method while decoding the flag. As a consequence, the returned flag may not actually be a valid flag.

Parameters:

input - where to read from

Returns:

the flag built from the data immediately read from the input

Throws:

java.io.IOException - if an IO exception is thrown while reading from the input

equals

public boolean equals(java.lang.Object o)

Overrides:

equals in class java.lang.Object

hashCode

public int hashCode()

Overrides:

hashCode in class java.lang.Object