Package org.apache.druid.frame.field

Class NumericFieldWriter

java.lang.Object

org.apache.druid.frame.field.NumericFieldWriter

All Implemented Interfaces:

Closeable, AutoCloseable, FieldWriter

Direct Known Subclasses:

DoubleFieldWriter, FloatFieldWriter, LongFieldWriter

public abstract class NumericFieldWriter
extends Object
implements FieldWriter

FieldWriter for numeric datatypes. The parent class does the null handling for the underlying data, while the individual subclasses write the individual element (long, float or double type). This also allows for a clean reuse of the readers and writers between the numeric types and also allowing the array writers (NumericArrayFieldWriter) to use these methods directly without duplication Format: - 1 byte: Whether the following value is null or not. Take a look at the note on the indicator bytes. - X bytes: Encoded value of the selector, or the default value if it is null. X denotes the size of the numeric value Indicator bytes for denoting whether the element is null or not null changes depending on whether the writer is used to write the data for individual value (like LONG) or for an element of an array (like ARRAY). This is because array support for the numeric types was added later and by then the field writers for individual fields were using 0x00 to denote the null byte, which is reserved for denoting the array end when we are writing the elements as part of the array instead. (0x00 is used for array end because it helps in preserving the byte comparison property of the numeric array field writers). Therefore, to preserve backward and forward compatibility, the individual element's writers were left unchanged, while the array's element's writers used 0x01 and 0x02 to denote null and non-null byte respectively Values produced by the writer are sortable without decoding

See Also:

• for examples of how this class serializes the field for numeric arrays

Field Summary

Fields

Modifier and Type	Field	Description
static final byte	ARRAY_ELEMENT_NOT_NULL_BYTE	Indicator byte denoting that the numeric value succeeding it is not null.
static final byte	ARRAY_ELEMENT_NULL_BYTE	Indicator byte denoting that the numeric value succeeding it is null.
static final byte	NOT_NULL_BYTE	Indicator byte denoting that the numeric value succeeding it is not null.
static final byte	NULL_BYTE	Indicator byte denoting that the numeric value succeeding it is null.

Constructor Summary

Constructors

Constructor	Description
NumericFieldWriter(BaseNullableColumnValueSelector selector, boolean forArray)

Method Summary

Modifier and Type	Method	Description
void	close()	Releases resources held by this writer.
abstract int	getNumericSizeBytes()
abstract void	writeNullToMemory(org.apache.datasketches.memory.WritableMemory memory, long position)	Writes the default value for the type to the memory.
abstract void	writeSelectorToMemory(org.apache.datasketches.memory.WritableMemory memory, long position)	Writes the value pointed by the selector to memory.
long	writeTo(org.apache.datasketches.memory.WritableMemory memory, long position, long maxSize)	Writes the current selection at the given memory position.

Methods inherited from class java.lang.Object

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

Field Details

NULL_BYTE

public static final byte NULL_BYTE

Indicator byte denoting that the numeric value succeeding it is null. This is used in the primitive writers. NULL_BYTE < NOT_NULL_BYTE to preserve the ordering while doing byte comparison

See Also:

• Constant Field Values

NOT_NULL_BYTE

public static final byte NOT_NULL_BYTE

Indicator byte denoting that the numeric value succeeding it is not null. This is used in the primitive writers

See Also:

• Constant Field Values

ARRAY_ELEMENT_NULL_BYTE

public static final byte ARRAY_ELEMENT_NULL_BYTE

Indicator byte denoting that the numeric value succeeding it is null. This is used while writing the individual elements writers of an array. ARRAY_ELEMENT_NULL_BYTE < ARRAY_ELEMENT_NOT_NULL_BYTE to preserve the ordering while doing byte comparison

See Also:

• Constant Field Values

ARRAY_ELEMENT_NOT_NULL_BYTE

public static final byte ARRAY_ELEMENT_NOT_NULL_BYTE

Indicator byte denoting that the numeric value succeeding it is not null. This is used while writing the individual elements writers of an array

See Also:

• Constant Field Values

Constructor Details

NumericFieldWriter

public NumericFieldWriter(BaseNullableColumnValueSelector selector,
 boolean forArray)

Method Details

writeTo

public long writeTo(org.apache.datasketches.memory.WritableMemory memory,
 long position,
 long maxSize)

Description copied from interface: FieldWriter

Writes the current selection at the given memory position.

Specified by:

writeTo in interface FieldWriter

Parameters:

memory - memory region in little-endian order

position - position to write

maxSize - maximum number of bytes to write

Returns:

number of bytes written, or -1 if "maxSize" was not enough memory

close

public void close()

Description copied from interface: FieldWriter

Releases resources held by this writer.

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Specified by:

close in interface FieldWriter

getNumericSizeBytes

public abstract int getNumericSizeBytes()

Returns:

The size in bytes of the numeric datatype that the implementation of this writer occupies

writeSelectorToMemory

public abstract void writeSelectorToMemory(org.apache.datasketches.memory.WritableMemory memory,
 long position)

Writes the value pointed by the selector to memory. The caller should ensure that the selector gives out the correct primitive type

writeNullToMemory

public abstract void writeNullToMemory(org.apache.datasketches.memory.WritableMemory memory,
 long position)

Writes the default value for the type to the memory. For long, it is 0L, for double, it is 0.0d etc. Useful mainly when the SQL incompatible mode is turned off, and maintains the fact that the size of the numeric field written doesn't vary irrespective of whether the value is null