Package org.apache.druid.query.rowsandcols.column

Class LimitedColumn

java.lang.Object

org.apache.druid.query.rowsandcols.column.LimitedColumn

All Implemented Interfaces:

Column

public class LimitedColumn
extends Object
implements Column

Constructor Summary

Constructors

Constructor	Description
LimitedColumn(Column column, int start, int end)

Method Summary

Modifier and Type	Method	Description
<T> T	as(Class<? extends T> clazz)	Asks the Column to return itself as a concrete implementation of a specific interface.
ColumnAccessor	toAccessor()	Returns the column as a ColumnAccessor.

Methods inherited from class java.lang.Object

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

Constructor Details

LimitedColumn

public LimitedColumn(Column column,
 int start,
 int end)

Method Details

toAccessor

@Nonnull
public ColumnAccessor toAccessor()

Description copied from interface: Column

Returns the column as a ColumnAccessor. Semantically, this would be equivalent to calling Column.as(ColumnAccessor.class). However, being able to implement this interface is part of the explicit contract of implementing this interface, so instead of relying on Column.as(java.lang.Class<? extends T>) which allows for returning null, we define a top-level method that should never return null.

Specified by:

toAccessor in interface Column

Returns:

a ColumnAccessor representation of the column, this should never return null.

as

@Nullable
public <T> T as(Class<? extends T> clazz)

Description copied from interface: Column

Asks the Column to return itself as a concrete implementation of a specific interface. The interface asked for will tend to be a semantically-meaningful interface. This method allows the calling code to interrogate the Column object about whether it can offer a meaningful optimization of the semantic interface. If a Column cannot do anything specifically optimal for the interface requested, it should return null instead of trying to come up with its own default implementation.

Specified by:

as in interface Column

Type Parameters:

T - The interface that the calling code wants a concrete implementation of

Parameters:

clazz - A class object representing the interface that the calling code wants a concrete implementation of

Returns:

A concrete implementation of the interface, or null if there is no meaningful optimization to be had through a local implementation of the interface.