org.apache.drill.exec.vector.accessor.reader

Class UnionReaderImpl

java.lang.Object

org.apache.drill.exec.vector.accessor.reader.UnionReaderImpl

All Implemented Interfaces:

ColumnReader, ReaderEvents, VariantReader

public class UnionReaderImpl
extends Object
implements VariantReader, ReaderEvents

Reader for a union vector. The union vector presents itself as a variant. This is an important, if subtle distinction. The current union vector format is highly inefficient (and buggy and not well supported in Drill's operators.) If the union concept is needed, then it should be redesigned, perhaps as a variable-width vector in which each entry consists of a type/value pair. (For variable-width values such as strings, the implementation would be a triple of (type, length, value). The API here is designed to abstract away the implementation and should work equally well for the current "union" implementation and the possible "variant" implementation. As a result, when changing the API, avoid introducing methods that assume an implementation.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	UnionReaderImpl.UnionObjectReader

Field Summary

Fields

Modifier and Type	Field and Description
protected NullStateReader	nullStateReader

Constructor Summary

Constructors

Constructor and Description
UnionReaderImpl(ColumnMetadata schema, VectorAccessor va, AbstractObjectReader[] variants)

Method Summary

Modifier and Type	Method and Description
ArrayReader	array()
void	bindBuffer()
void	bindIndex(ColumnReaderIndex index)
void	bindNullState(NullStateReader nullStateReader)
static AbstractObjectReader	build(ColumnMetadata schema, VectorAccessor va, AbstractObjectReader[] variants)
TypeProtos.MinorType	dataType() Return the data type of the current value.
String	getAsString() Return the entire object as a string.
Object	getObject() Return the value of the underlying data as a Java object.
boolean	hasType(TypeProtos.MinorType type) Determine if a given type is supported by the union vector for some value in the result set.
boolean	isNull() Determine if this value is null.
ObjectReader	member() Return the reader for the member type of the current row.
ObjectReader	member(TypeProtos.MinorType type) Return the member reader for the given type.
NullStateReader	nullStateReader()
void	reposition()
ScalarReader	scalar() Return the appropriate scalar reader for the current value.
ScalarReader	scalar(TypeProtos.MinorType type) Return the scalar reader for the given type member.
ColumnMetadata	schema()
int	size()
TupleReader	tuple()
ObjectType	type() The type of this reader.
VariantMetadata	variantSchema()

Methods inherited from class java.lang.Object

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

Field Detail

nullStateReader

protected NullStateReader nullStateReader

Constructor Detail

UnionReaderImpl

public UnionReaderImpl(ColumnMetadata schema,
                       VectorAccessor va,
                       AbstractObjectReader[] variants)

Method Detail

build

public static AbstractObjectReader build(ColumnMetadata schema,
                                         VectorAccessor va,
                                         AbstractObjectReader[] variants)

bindNullState

public void bindNullState(NullStateReader nullStateReader)

Specified by:

bindNullState in interface ReaderEvents

nullStateReader

public NullStateReader nullStateReader()

Specified by:

nullStateReader in interface ReaderEvents

bindIndex

public void bindIndex(ColumnReaderIndex index)

Specified by:

bindIndex in interface ReaderEvents

type

public ObjectType type()

Description copied from interface: ColumnReader

The type of this reader.

Specified by:

type in interface ColumnReader

Returns:

type of reader

schema

public ColumnMetadata schema()

Specified by:

schema in interface ColumnReader

variantSchema

public VariantMetadata variantSchema()

Specified by:

variantSchema in interface VariantReader

size

public int size()

Specified by:

size in interface VariantReader

hasType

public boolean hasType(TypeProtos.MinorType type)

Description copied from interface: VariantReader

Determine if a given type is supported by the union vector for some value in the result set.

Specified by:

hasType in interface VariantReader

Parameters:

type - the Drill minor type to query

Returns:

true if a reader for the given type is available, false if a request for a reader of that type will return null.

reposition

public void reposition()

Specified by:

reposition in interface ReaderEvents

bindBuffer

public void bindBuffer()

Specified by:

bindBuffer in interface ReaderEvents

isNull

public boolean isNull()

Description copied from interface: ColumnReader

Determine if this value is null.

• Nullable scalar: determine if the value is null.
• Non-nullable scalar: always returns false.
• Arrays: always returns false
• Lists: determine if the list for the current row is null. In a list, an array entry can be null, empty, or can contain items. In repeated types, the array itself is never null. If the array is null, then it implicitly has no entries.
• Map or Repeated Map: Always returns false.
• Map inside a union, or in a list that contains a union, the tuple itself can be null.
• Union: Determine if the current value is null. Null values have no type and no associated reader.

Specified by:

isNull in interface ColumnReader

Returns:

true if this value is null; false otherwise

dataType

public TypeProtos.MinorType dataType()

Description copied from interface: VariantReader

Return the data type of the current value. (What happens if the row is null, must it be a null of some type?)

Specified by:

dataType in interface VariantReader

Returns:

data type of the current data value

member

public ObjectReader member(TypeProtos.MinorType type)

Description copied from interface: VariantReader

Return the member reader for the given type. The type must be a member of the union. Allows caching readers across rows.

Specified by:

member in interface VariantReader

Parameters:

type - member type

Returns:

reader for that type

scalar

public ScalarReader scalar(TypeProtos.MinorType type)

Description copied from interface: VariantReader

Return the scalar reader for the given type member. The type must be a member of the union. Allows caching readers across rows. Identical to:
>member(type).scalar()

Specified by:

scalar in interface VariantReader

Parameters:

type - member type

Returns:

scalar reader for that type

member

public ObjectReader member()

Description copied from interface: VariantReader

Return the reader for the member type of the current row. Same as:
member(dataType())

Specified by:

member in interface VariantReader

Returns:

reader for the member type of the current row.

scalar

public ScalarReader scalar()

Description copied from interface: VariantReader

Return the appropriate scalar reader for the current value.

Specified by:

scalar in interface VariantReader

Returns:

null if ColumnReader.isNull() returns true, else the equivalent of scalar( VariantReader.dataType() )

tuple

public TupleReader tuple()

Specified by:

tuple in interface VariantReader

array

public ArrayReader array()

Specified by:

array in interface VariantReader

getObject

public Object getObject()

Description copied from interface: ColumnReader

Return the value of the underlying data as a Java object. Primarily for testing

• Array: Return the entire array as an List of objects. Note, even if the array is scalar, the elements are still returned as a list.

Specified by:

getObject in interface ColumnReader

Returns:

the value as a Java object

getAsString

public String getAsString()

Description copied from interface: ColumnReader

Return the entire object as a string. Primarily for debugging.

Specified by:

getAsString in interface ColumnReader

Returns:

string representation of the object