org.apache.drill.exec.vector.accessor

Interface ObjectWriter

All Superinterfaces:

ColumnWriter

All Known Implementing Classes:

AbstractArrayWriter.ArrayObjectWriter, AbstractObjectWriter, AbstractScalarWriterImpl.ScalarObjectWriter, AbstractTupleWriter.TupleObjectWriter, DictEntryWriter.DictEntryObjectWriter, ObjectDictWriter.DictObjectWriter, UnionWriterImpl.VariantObjectWriter

public interface ObjectWriter
extends ColumnWriter

Represents a column within a tuple. A column can be an array, a scalar or a tuple. Each has an associated column metadata (schema) and a writer. The writer is one of three kinds, depending on the kind of the column. If the column is a map, then the column also has an associated tuple loader to define and write to the tuple.

This interface defines a writer to set values for value vectors using a simple, uniform interface modeled after a JSON object. Every column value is an object of one of three types: scalar, array or tuple. Methods exist to "cast" this object to the proper type. This model allows a very simple representation: tuples (rows, maps) consist of objects. Arrays are lists of objects.

Every column resides at an index, is defined by a schema, is backed by a value vector, and and is written to by a writer. Each column also tracks the schema version in which it was added to detect schema evolution. Each column has an optional overflow vector that holds overflow record values when a batch becomes full.

ObjectReader

Method Summary

Modifier and Type	Method and Description
ArrayWriter	array()
DictWriter	dict()
WriterEvents	events() The internal state behind this writer.
ScalarWriter	scalar()
TupleWriter	tuple()
VariantWriter	variant()
ColumnWriter	writer() Generic version of the above, for dynamic handling of writers.

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

copy, isProjected, nullable, schema, setNull, setObject, type

Method Detail

scalar

ScalarWriter scalar()

tuple

TupleWriter tuple()

array

ArrayWriter array()

variant

VariantWriter variant()

dict

DictWriter dict()

writer

ColumnWriter writer()

Generic version of the above, for dynamic handling of writers.

Returns:

the generic form of the column writer

events

WriterEvents events()

The internal state behind this writer. To be used only by the implementation, not by the client.