uk.ac.starlink.parquet

Interface Decoder<T>

public interface Decoder<T>

Can read values from a particular column in a parquet file. Instances of this class should not be used from multiple threads concurrently.

Since:

24 Feb 2021

Author:

Mark Taylor

Method Summary

Modifier and Type	Method and Description
void	clearValue() Resets this reader to the state in which no reads have been called.
Class<T>	getContentClass() Class of object that is read from column data.
T	getValue() Returns the value that has been read into this reader.
void	readItem(org.apache.parquet.column.ColumnReader crdr) Reads a primitive value from the supplied column reader into this decoder's current value.
void	readNull() Reads a null value into this decoder's current value.

Method Detail

getContentClass

Class<T> getContentClass()

Class of object that is read from column data.

Returns:

content class

readItem

void readItem(org.apache.parquet.column.ColumnReader crdr)

Reads a primitive value from the supplied column reader into this decoder's current value.

Parameters:

crdr - column reader with a primitive value ready to read

readNull

void readNull()

Reads a null value into this decoder's current value.

clearValue

void clearValue()

Resets this reader to the state in which no reads have been called.

getValue

T getValue()

Returns the value that has been read into this reader. It will be the result of all the readItem and readNull() calls since the last call to clearValue() (in the case of a scalar value, there will only have been one such call).

Returns:

value of the most recently read column cell