org.apache.parquet.column.values

Class ValuesReader

java.lang.Object

org.apache.parquet.column.values.ValuesReader

Direct Known Subclasses:

BinaryPlainValuesReader, BitPackingValuesReader, BooleanPlainValuesReader, ByteBitPackingValuesReader, DeltaBinaryPackingValuesReader, DeltaByteArrayReader, DeltaLengthByteArrayValuesReader, DictionaryValuesReader, FixedLenByteArrayPlainValuesReader, PlainValuesReader, RunLengthBitPackingHybridValuesReader, ZeroIntegerValuesReader

public abstract class ValuesReader
extends Object

Base class to implement an encoding for a given column type. A ValuesReader is provided with a page (byte-array) and is responsible for deserializing the primitive values stored in that page. Given that pages are homogeneous (store only a single type), typical subclasses will only override one of the read*() methods.

Author:

Julien Le Dem

Constructor Summary

Constructors

Constructor and Description
ValuesReader()

Method Summary

Methods

Modifier and Type	Method and Description
int	getNextOffset() Called to return offset of the next section
abstract void	initFromPage(int valueCount, byte[] page, int offset) Called to initialize the column reader from a part of a page.
boolean	readBoolean()
Binary	readBytes()
double	readDouble()
float	readFloat()
int	readInteger()
long	readLong()
int	readValueDictionaryId() usable when the encoding is dictionary based
abstract void	skip() Skips the next value in the page

Methods inherited from class java.lang.Object

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

Constructor Detail

ValuesReader

public ValuesReader()

Method Detail

initFromPage

public abstract void initFromPage(int valueCount,
                byte[] page,
                int offset)
                           throws IOException

Called to initialize the column reader from a part of a page. The underlying implementation knows how much data to read, so a length is not provided. Each page may contain several sections:

• repetition levels column
• definition levels column
• data column

This function is called with 'offset' pointing to the beginning of one of these sections, and should return the offset to the section following it.

Parameters:

valueCount - count of values in this page

page - the array to read from containing the page data (repetition levels, definition levels, data)

offset - where to start reading from in the page

Throws:

IOException

getNextOffset

public int getNextOffset()

Called to return offset of the next section

Returns:

offset of the next section

readValueDictionaryId

public int readValueDictionaryId()

usable when the encoding is dictionary based

Returns:

the id of the next value from the page

readBoolean

public boolean readBoolean()

Returns:

the next boolean from the page

readBytes

public Binary readBytes()

Returns:

the next Binary from the page

readFloat

public float readFloat()

Returns:

the next float from the page

readDouble

public double readDouble()

Returns:

the next double from the page

readInteger

public int readInteger()

Returns:

the next integer from the page

readLong

public long readLong()

Returns:

the next long from the page

skip

public abstract void skip()

Skips the next value in the page