org.apache.drill.exec.vector.accessor

Interface ArrayReader

All Superinterfaces:

ColumnReader

All Known Subinterfaces:

DictReader

All Known Implementing Classes:

ArrayReaderImpl, DictReaderImpl

public interface ArrayReader
extends ColumnReader

Generic array reader. An array is one of the following:

• Array of scalars. Read the values using #elements(), which provides an array-like access to the scalars.
• A repeated map. Use #tuple(int) to get a tuple reader for a specific array element. Use size() to learn the number of maps in the array.
• List of lists. Use the #array(int) method to get the nested list at a given index. Use size() to learn the number of maps in the array.

ArrayWriter

Method Summary

Modifier and Type	Method and Description
ArrayReader	array()
ObjectReader	entry() Return the generic object reader for the array element.
ObjectType	entryType() The object type of the list entry.
boolean	next() Move forward one position.
void	rewind()
ScalarReader	scalar()
void	setPosn(int index) Set the array reader to read a given array entry.
int	size() Number of elements in the array.
TupleReader	tuple()
VariantReader	variant()

Methods inherited from interface org.apache.drill.exec.vector.accessor.ColumnReader

getAsString, getObject, isNull, schema, type

Method Detail

size

int size()

Number of elements in the array.

Returns:

the number of elements

entryType

ObjectType entryType()

The object type of the list entry. All entries have the same type.

Returns:

the object type of each entry

entry

ObjectReader entry()

Return the generic object reader for the array element. This version does not position the reader, the client must call setPosn(int) to set the position. This form allows up-front setup of the readers when convenient for the caller.

scalar

ScalarReader scalar()

tuple

TupleReader tuple()

array

ArrayReader array()

variant

VariantReader variant()

setPosn

void setPosn(int index)

Set the array reader to read a given array entry. Not used for scalars, only for maps and arrays when using the non-indexed methods entry(), tuple() and array().

rewind

void rewind()

next

boolean next()

Move forward one position.

Returns:

true if another position is available, false if the end of the array is reached