org.apache.parquet.column.values.deltastrings

Class DeltaByteArrayReader

java.lang.Object

org.apache.parquet.column.values.ValuesReader

org.apache.parquet.column.values.deltastrings.DeltaByteArrayReader

All Implemented Interfaces:

RequiresPreviousReader

public class DeltaByteArrayReader
extends ValuesReader
implements RequiresPreviousReader

Reads binary data written by DeltaByteArrayWriter

Author:

Aniket Mokashi

Constructor Summary

Constructors

Constructor and Description
DeltaByteArrayReader()

Method Summary

Modifier and Type	Method and Description
void	initFromPage(int valueCount, ByteBuffer page, int offset) Called to initialize the column reader from a part of a page.
Binary	readBytes()
void	setPreviousReader(ValuesReader reader) There was a bug (PARQUET-246) in which DeltaByteArrayWriter's reset() method did not clear the previous value state that it tracks internally.
void	skip() Skips the next value in the page

Methods inherited from class org.apache.parquet.column.values.ValuesReader

getNextOffset, initFromPage, readBoolean, readDouble, readFloat, readInteger, readLong, readValueDictionaryId

Methods inherited from class java.lang.Object

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

Constructor Detail

DeltaByteArrayReader

public DeltaByteArrayReader()

Method Detail

initFromPage

public void initFromPage(int valueCount,
                         ByteBuffer page,
                         int offset)
                  throws IOException

Description copied from class: ValuesReader

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.

Specified by:

initFromPage in class ValuesReader

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

skip

public void skip()

Description copied from class: ValuesReader

Skips the next value in the page

Specified by:

skip in class ValuesReader

readBytes

public Binary readBytes()

Overrides:

readBytes in class ValuesReader

Returns:

the next Binary from the page

setPreviousReader

public void setPreviousReader(ValuesReader reader)

There was a bug (PARQUET-246) in which DeltaByteArrayWriter's reset() method did not clear the previous value state that it tracks internally. This resulted in the first value of all pages (except for the first page) to be a delta from the last value of the previous page. In order to read corrupted files written with this bug, when reading a new page we need to recover the previous page's last value to use it (if needed) to read the first value.

Specified by:

setPreviousReader in interface RequiresPreviousReader