org.apache.drill.exec.vector.accessor

Interface ColumnReader

All Known Subinterfaces:

ArrayReader, DictReader, ObjectReader, RowSetReader, ScalarReader, TupleReader, VariantReader

All Known Implementing Classes:

AbstractObjectReader, AbstractScalarReader, AbstractScalarReader.NullReader, AbstractScalarReader.ScalarObjectReader, AbstractTupleReader, AbstractTupleReader.TupleObjectReader, ArrayReaderImpl, ArrayReaderImpl.ArrayObjectReader, BaseScalarReader, BaseScalarReader.BaseFixedWidthReader, BaseScalarReader.BaseVarWidthReader, BitColumnReader, ColumnAccessors.BigIntColumnReader, ColumnAccessors.DateColumnReader, ColumnAccessors.Decimal18ColumnReader, ColumnAccessors.Decimal28SparseColumnReader, ColumnAccessors.Decimal38SparseColumnReader, ColumnAccessors.Decimal9ColumnReader, ColumnAccessors.Float4ColumnReader, ColumnAccessors.Float8ColumnReader, ColumnAccessors.IntColumnReader, ColumnAccessors.IntervalColumnReader, ColumnAccessors.IntervalDayColumnReader, ColumnAccessors.IntervalYearColumnReader, ColumnAccessors.SmallIntColumnReader, ColumnAccessors.TimeColumnReader, ColumnAccessors.TimeStampColumnReader, ColumnAccessors.TinyIntColumnReader, ColumnAccessors.UInt1ColumnReader, ColumnAccessors.UInt2ColumnReader, ColumnAccessors.UInt4ColumnReader, ColumnAccessors.UInt8ColumnReader, ColumnAccessors.Var16CharColumnReader, ColumnAccessors.VarBinaryColumnReader, ColumnAccessors.VarCharColumnReader, ColumnAccessors.VarDecimalColumnReader, DictEntryReader, DictReaderImpl, DictReaderImpl.DictObjectReader, MapReader, OffsetVectorReader, RowSetReaderImpl, UnionReaderImpl, UnionReaderImpl.UnionObjectReader

public interface ColumnReader

Base interface for all column readers, defining a generic set of methods that all readers provide. In particular, given the metadata and the object type, one can determine what to do with each reader when working with readers generically. The getObject() and getAsString() methods provide generic data access for tests and debugging.

Method Summary

Modifier and Type	Method and Description
String	getAsString() Return the entire object as a string.
Object	getObject() Return the value of the underlying data as a Java object.
boolean	isNull() Determine if this value is null.
ColumnMetadata	schema()
ObjectType	type() The type of this reader.

Method Detail

schema

ColumnMetadata schema()

type

ObjectType type()

The type of this reader.

Returns:

type of reader

isNull

boolean isNull()

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.

Returns:

true if this value is null; false otherwise

getObject

Object getObject()

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.

Returns:

the value as a Java object

getAsString

String getAsString()

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

Returns:

string representation of the object