Package org.apache.druid.frame.field

Class NumericArrayFieldWriter

java.lang.Object

org.apache.druid.frame.field.NumericArrayFieldWriter

All Implemented Interfaces:

Closeable, AutoCloseable, FieldWriter

public class NumericArrayFieldWriter
extends Object
implements FieldWriter

Writes the values of the type ARRAY where X is a numeric type to row based frames. The format of the array written is as follows:

Format: - 1 Byte - NULL_ROW or NON_NULL_ROW denoting whether the array itself is null - If the array is null, then the writer stops here - If the array is not null, then it proceeds to the following steps

For each value in the non-null array: - 1 Byte - NumericFieldWriter.ARRAY_ELEMENT_NULL_BYTE or NumericFieldWriter.ARRAY_ELEMENT_NOT_NULL_BYTE denothing whether the proceeding value is null or not. - ElementSize Bytes - The encoded value of the element

Once all the values in the non-null arrays are over, writes ARRAY_TERMINATOR. This is to aid the byte comparison, and also let the reader know that the number of elements in the array are over.

The format doesn't add the number of elements in the array at the beginning, so that the serialization of the arrays are byte-by-byte comparable.

Examples: 1. null | Bytes | Value | Interpretation | |--------|-------|-----------------------------| | 1 | 0x00 | Denotes that the array null |

2. [] (empty array) | Bytes | Value | Interpretation | |--------|----- -|------------------------------------| | 1 | 0x01 | Denotes that the array is not null | | 2 | 0x00 | End of the array |

3. [5L, null, 6L] | Bytes | Value | Interpretation | |---------|--------------|-----------------------------------------------------------------------------------| | 1 | 0x01 | Denotes that the array is not null | | 2 | 0x02 | Denotes that the next element is not null | | 3-10 | transform(5) | Representation of 5 | | 11 | 0x01 | Denotes that the next element is null | | 12-19 | transform(0) | Representation of 0 (default value, the reader will ignore it if SqlCompatible mode is on | | 20 | 0x02 | Denotes that the next element is not null | | 21-28 | transform(6) | Representation of 6 | | 29 | 0x00 | End of array |

Field Summary

Fields

Modifier and Type	Field	Description
static byte	ARRAY_TERMINATOR	Marks the end of the array.
static byte	NON_NULL_ROW	Denotes that the array is non null
static byte	NULL_ROW	Denotes that the array itself is null

Constructor Summary

Constructors

Constructor	Description
NumericArrayFieldWriter(ColumnValueSelector selector, NumericFieldWriterFactory writerFactory)

Method Summary

Modifier and Type	Method	Description
void	close()	Releases resources held by this writer.
static NumericArrayFieldWriter	getDoubleArrayFieldWriter(ColumnValueSelector selector)	Returns the writer for ARRAY
static NumericArrayFieldWriter	getFloatArrayFieldWriter(ColumnValueSelector selector)	Returns the writer for ARRAY
static NumericArrayFieldWriter	getLongArrayFieldWriter(ColumnValueSelector selector)	Returns the writer for ARRAY
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 Detail

NULL_ROW

public static final byte NULL_ROW

Denotes that the array itself is null

See Also:

Constant Field Values

NON_NULL_ROW

public static final byte NON_NULL_ROW

Denotes that the array is non null

See Also:

Constant Field Values

ARRAY_TERMINATOR

public static final byte ARRAY_TERMINATOR

Marks the end of the array. Since NULL_ROW and ARRAY_TERMINATOR will only occur at different locations, therefore there is no clash in keeping both's values at 0x00

See Also:

Constant Field Values

Constructor Detail

NumericArrayFieldWriter

public NumericArrayFieldWriter(ColumnValueSelector selector,
                               NumericFieldWriterFactory writerFactory)

Method Detail

getLongArrayFieldWriter

public static NumericArrayFieldWriter getLongArrayFieldWriter(ColumnValueSelector selector)

Returns the writer for ARRAY

getFloatArrayFieldWriter

public static NumericArrayFieldWriter getFloatArrayFieldWriter(ColumnValueSelector selector)

Returns the writer for ARRAY

getDoubleArrayFieldWriter

public static NumericArrayFieldWriter getDoubleArrayFieldWriter(ColumnValueSelector selector)

Returns the writer for ARRAY

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