io.druid.segment.virtual

Class ExpressionVirtualColumn

java.lang.Object

io.druid.segment.virtual.ExpressionVirtualColumn

All Implemented Interfaces:

Cacheable, VirtualColumn

public class ExpressionVirtualColumn
extends Object
implements VirtualColumn

Constructor Summary

Constructors

Constructor and Description
ExpressionVirtualColumn(String name, String expression)

Method Summary

Modifier and Type	Method and Description
ColumnCapabilities	capabilities(String columnName) Returns the capabilities of this virtual column, which includes a type that should match the type returned by "makeObjectColumnSelector" and should correspond to the best performing selector.
boolean	equals(Object o)
byte[]	getCacheKey() Get a byte array used as a cache key.
String	getExpression()
String	getOutputName() Output name of this column.
int	hashCode()
DimensionSelector	makeDimensionSelector(DimensionSpec dimensionSpec, ColumnSelectorFactory columnSelectorFactory) Build a selector corresponding to this virtual column.
FloatColumnSelector	makeFloatColumnSelector(String columnName, ColumnSelectorFactory columnSelectorFactory) Build a selector corresponding to this virtual column.
LongColumnSelector	makeLongColumnSelector(String columnName, ColumnSelectorFactory columnSelectorFactory) Build a selector corresponding to this virtual column.
ObjectColumnSelector	makeObjectColumnSelector(String columnName, ColumnSelectorFactory columnSelectorFactory) Build a selector corresponding to this virtual column.
List<String>	requiredColumns() Returns a list of columns that this virtual column will access.
String	toString()
boolean	usesDotNotation() Indicates that this virtual column can be referenced with dot notation.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

ExpressionVirtualColumn

public ExpressionVirtualColumn(String name,
                               String expression)

Method Detail

getOutputName

public String getOutputName()

Description copied from interface: VirtualColumn

Output name of this column.

Specified by:

getOutputName in interface VirtualColumn

Returns:

name

getExpression

public String getExpression()

makeObjectColumnSelector

public ObjectColumnSelector makeObjectColumnSelector(String columnName,
                                                     ColumnSelectorFactory columnSelectorFactory)

Description copied from interface: VirtualColumn

Build a selector corresponding to this virtual column. Also provides the name that the virtual column was referenced with, which is useful if this column uses dot notation.

Specified by:

makeObjectColumnSelector in interface VirtualColumn

Parameters:

columnName - the name this virtual column was referenced with

columnSelectorFactory - column selector factory

Returns:

the selector, must not be null

makeDimensionSelector

public DimensionSelector makeDimensionSelector(DimensionSpec dimensionSpec,
                                               ColumnSelectorFactory columnSelectorFactory)

Description copied from interface: VirtualColumn

Build a selector corresponding to this virtual column. Also provides the name that the virtual column was referenced with (through DimensionSpec.getDimension(), which is useful if this column uses dot notation. The virtual column is expected to apply any necessary decoration from the dimensionSpec.

Specified by:

makeDimensionSelector in interface VirtualColumn

Parameters:

dimensionSpec - the dimensionSpec this column was referenced with

columnSelectorFactory - column selector factory

Returns:

the selector, or null if we can't make a selector

makeFloatColumnSelector

public FloatColumnSelector makeFloatColumnSelector(String columnName,
                                                   ColumnSelectorFactory columnSelectorFactory)

Description copied from interface: VirtualColumn

Build a selector corresponding to this virtual column. Also provides the name that the virtual column was referenced with, which is useful if this column uses dot notation.

Specified by:

makeFloatColumnSelector in interface VirtualColumn

Parameters:

columnName - the name this virtual column was referenced with

columnSelectorFactory - column selector factory

Returns:

the selector, or null if we can't make a selector

makeLongColumnSelector

public LongColumnSelector makeLongColumnSelector(String columnName,
                                                 ColumnSelectorFactory columnSelectorFactory)

Description copied from interface: VirtualColumn

Build a selector corresponding to this virtual column. Also provides the name that the virtual column was referenced with, which is useful if this column uses dot notation.

Specified by:

makeLongColumnSelector in interface VirtualColumn

Parameters:

columnName - the name this virtual column was referenced with

columnSelectorFactory - column selector factory

Returns:

the selector, or null if we can't make a selector

capabilities

public ColumnCapabilities capabilities(String columnName)

Description copied from interface: VirtualColumn

Returns the capabilities of this virtual column, which includes a type that should match the type returned by "makeObjectColumnSelector" and should correspond to the best performing selector. May vary based on columnName if this column uses dot notation.

Specified by:

capabilities in interface VirtualColumn

Parameters:

columnName - the name this virtual column was referenced with

Returns:

capabilities, must not be null

requiredColumns

public List<String> requiredColumns()

Description copied from interface: VirtualColumn

Returns a list of columns that this virtual column will access. This may include the names of other virtual columns. May be empty if a virtual column doesn't access any underlying columns. Does not pass columnName because there is an assumption that the list of columns needed by a dot-notation supporting virtual column will not vary based on the columnName.

Specified by:

requiredColumns in interface VirtualColumn

Returns:

column names

usesDotNotation

public boolean usesDotNotation()

Description copied from interface: VirtualColumn

Indicates that this virtual column can be referenced with dot notation. For example, a virtual column named "foo" could be referred to as "foo.bar" with the Cursor it is registered with. In that case, init will be called with columnName "foo.bar" rather than "foo".

Specified by:

usesDotNotation in interface VirtualColumn

Returns:

whether to use dot notation

getCacheKey

public byte[] getCacheKey()

Description copied from interface: Cacheable

Get a byte array used as a cache key.

Specified by:

getCacheKey in interface Cacheable

Returns:

a cache key

equals

public boolean equals(Object o)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

toString

public String toString()

Overrides:

toString in class Object