Package org.apache.druid.segment.virtual

Class ExpressionVirtualColumn

java.lang.Object

org.apache.druid.segment.virtual.ExpressionVirtualColumn

All Implemented Interfaces:

Cacheable, VirtualColumn

public class ExpressionVirtualColumn
extends Object
implements VirtualColumn

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.druid.segment.VirtualColumn

VirtualColumn.EquivalenceKey

Constructor Summary

Constructors

Constructor	Description
ExpressionVirtualColumn(String name, String expression, Expr parsedExpression, ColumnType outputType)	Constructor for creating an ExpressionVirtualColumn from a pre-parsed-and-analyzed expression, where the original expression string is known.
ExpressionVirtualColumn(String name, String expression, ColumnType outputType, ExprMacroTable macroTable)	Constructor for deserialization.
ExpressionVirtualColumn(String name, Expr parsedExpression, ColumnType outputType)	Constructor for creating an ExpressionVirtualColumn from a pre-parsed expression, where the original expression string is not known.

Method Summary

Modifier and Type	Method	Description
boolean	canVectorize(ColumnInspector inspector)
ColumnCapabilities	capabilities(String columnName)	This method is deprecated in favor of VirtualColumn.capabilities(ColumnInspector, String), which should be used whenever possible and can support virtual column implementations that need to inspect other columns as inputs.
ColumnCapabilities	capabilities(ColumnInspector inspector, String columnName)	Return the ColumnCapabilities which best describe the optimal selector to read from this virtual column.
boolean	equals(Object o)
byte[]	getCacheKey()	Get a byte array used as a cache key.
VirtualColumn.EquivalenceKey	getEquivalanceKey()	Returns a key used for "equivalence" comparisons, for checking if some virtual column is equivalent to some other virtual column, regardless of the output name.
String	getExpression()
ColumnIndexSupplier	getIndexSupplier(String columnName, ColumnIndexSelector columnIndexSelector)	Get the ColumnIndexSupplier of the specified virtual column, with the assistance of a ColumnSelector to allow reading things from segments.
String	getOutputName()	Output name of this column.
ColumnType	getOutputType()
com.google.common.base.Supplier<Expr>	getParsedExpression()
int	hashCode()
ColumnValueSelector<?>	makeColumnValueSelector(String columnName, ColumnSelectorFactory factory)
DimensionSelector	makeDimensionSelector(DimensionSpec dimensionSpec, ColumnSelectorFactory columnSelectorFactory)
GroupByVectorColumnSelector	makeGroupByVectorColumnSelector(String columnName, VectorColumnSelectorFactory factory, DeferExpressionDimensions deferExpressionDimensions)	Returns a group-by selector.
SingleValueDimensionVectorSelector	makeSingleValueVectorDimensionSelector(DimensionSpec dimensionSpec, VectorColumnSelectorFactory factory)
VectorObjectSelector	makeVectorObjectSelector(String columnName, VectorColumnSelectorFactory factory)
VectorValueSelector	makeVectorValueSelector(String columnName, VectorColumnSelectorFactory factory)
List<String>	requiredColumns()	Returns a list of columns that this virtual column will access.
VirtualColumn	rewriteRequiredColumns(Map<String,String> columnRewrites)	Return a copy of this virtual column that is identical to this virtual column except that it operates on different columns, based on a renaming map where the key is the column to be renamed and the value is the new column.
boolean	supportsRequiredRewrite()	Returns true if the virtual column supports VirtualColumn.rewriteRequiredColumns(Map)
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

Methods inherited from interface org.apache.druid.segment.VirtualColumn

makeColumnValueSelector, makeColumnValueSelector, makeDimensionSelector, makeDimensionSelector, makeMultiValueVectorDimensionSelector, makeMultiValueVectorDimensionSelector, makeMultiValueVectorDimensionSelector, makeSingleValueVectorDimensionSelector, makeSingleValueVectorDimensionSelector, makeVectorObjectSelector, makeVectorObjectSelector, makeVectorValueSelector, makeVectorValueSelector, toSelectableColumn

Constructor Details

ExpressionVirtualColumn

public ExpressionVirtualColumn(String name,
 String expression,
 @Nullable
 ColumnType outputType,
 ExprMacroTable macroTable)

Constructor for deserialization.

ExpressionVirtualColumn

public ExpressionVirtualColumn(String name,
 String expression,
 Expr parsedExpression,
 @Nullable
 ColumnType outputType)

Constructor for creating an ExpressionVirtualColumn from a pre-parsed-and-analyzed expression, where the original expression string is known.

ExpressionVirtualColumn

public ExpressionVirtualColumn(String name,
 Expr parsedExpression,
 @Nullable
 ColumnType outputType)

Constructor for creating an ExpressionVirtualColumn from a pre-parsed expression, where the original expression string is not known. Instead, it is generated by Expr.stringify().

Method Details

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()

getOutputType

@Nullable
public ColumnType getOutputType()

getParsedExpression

public com.google.common.base.Supplier<Expr> getParsedExpression()

makeDimensionSelector

public DimensionSelector makeDimensionSelector(DimensionSpec dimensionSpec,
 ColumnSelectorFactory columnSelectorFactory)

Specified by:

makeDimensionSelector in interface VirtualColumn

makeColumnValueSelector

public ColumnValueSelector<?> makeColumnValueSelector(String columnName,
 ColumnSelectorFactory factory)

Specified by:

makeColumnValueSelector in interface VirtualColumn

canVectorize

public boolean canVectorize(ColumnInspector inspector)

Specified by:

canVectorize in interface VirtualColumn

makeSingleValueVectorDimensionSelector

public SingleValueDimensionVectorSelector makeSingleValueVectorDimensionSelector(DimensionSpec dimensionSpec,
 VectorColumnSelectorFactory factory)

Specified by:

makeSingleValueVectorDimensionSelector in interface VirtualColumn

makeVectorValueSelector

public VectorValueSelector makeVectorValueSelector(String columnName,
 VectorColumnSelectorFactory factory)

Specified by:

makeVectorValueSelector in interface VirtualColumn

makeVectorObjectSelector

public VectorObjectSelector makeVectorObjectSelector(String columnName,
 VectorColumnSelectorFactory factory)

Specified by:

makeVectorObjectSelector in interface VirtualColumn

makeGroupByVectorColumnSelector

@Nullable
public GroupByVectorColumnSelector makeGroupByVectorColumnSelector(String columnName,
 VectorColumnSelectorFactory factory,
 DeferExpressionDimensions deferExpressionDimensions)

Description copied from interface: VirtualColumn

Returns a group-by selector. Allows virtual columns to control their own grouping behavior.

Specified by:

makeGroupByVectorColumnSelector in interface VirtualColumn

Parameters:

columnName - column name

factory - column selector factory

deferExpressionDimensions - active value of GroupByQueryConfig.CTX_KEY_DEFER_EXPRESSION_DIMENSIONS

Returns:

selector, or null if this virtual column does not have a specialized one

getIndexSupplier

@Nullable
public ColumnIndexSupplier getIndexSupplier(String columnName,
 ColumnIndexSelector columnIndexSelector)

Description copied from interface: VirtualColumn

Get the ColumnIndexSupplier of the specified virtual column, with the assistance of a ColumnSelector to allow reading things from segments. Returns null if the virtual column wants to act like a missing column. Returns NoIndexesColumnIndexSupplier.getInstance() if the virtual column does not support indexes and wants cursor-based filtering.

Specified by:

getIndexSupplier in interface VirtualColumn

capabilities

public ColumnCapabilities capabilities(String columnName)

Description copied from interface: VirtualColumn

This method is deprecated in favor of VirtualColumn.capabilities(ColumnInspector, String), which should be used whenever possible and can support virtual column implementations that need to inspect other columns as inputs. This is a fallback implementation to return the capabilities of this virtual column, which includes a type that corresponds to the best performing base selector supertype (e. g. BaseLongColumnValueSelector) of the object, returned from VirtualColumn.makeColumnValueSelector(String, ColumnSelectorFactory). 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

capabilities

@Nullable
public ColumnCapabilities capabilities(ColumnInspector inspector,
 String columnName)

Description copied from interface: VirtualColumn

Return the ColumnCapabilities which best describe the optimal selector to read from this virtual column.

The ColumnInspector (most likely corresponding to an underlying ColumnSelectorFactory of a query) allows the virtual column to consider this information if necessary to compute its output type details.

Examples of this include the ExpressionVirtualColumn, which takes input from other columns and uses the ColumnInspector to infer the output type of expressions based on the types of the inputs.

Specified by:

capabilities in interface VirtualColumn

Parameters:

inspector - column inspector to provide additional information of other available columns

columnName - the name this virtual column was referenced with

Returns:

capabilities, or null if the column should be treated as if it doesn't exist.

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

supportsRequiredRewrite

public boolean supportsRequiredRewrite()

Description copied from interface: VirtualColumn

Returns true if the virtual column supports VirtualColumn.rewriteRequiredColumns(Map)

Specified by:

supportsRequiredRewrite in interface VirtualColumn

rewriteRequiredColumns

public VirtualColumn rewriteRequiredColumns(Map<String,String> columnRewrites)

Description copied from interface: VirtualColumn

Return a copy of this virtual column that is identical to this virtual column except that it operates on different columns, based on a renaming map where the key is the column to be renamed and the value is the new column. Callers should check VirtualColumn.supportsRequiredRewrite() first to ensure that this method is supported.

Specified by:

rewriteRequiredColumns in interface VirtualColumn

Parameters:

columnRewrites - Column rewrite map

Returns:

Copy of this virtual column that operates on new columns based on the rewrite map

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:

bytes to be used as cache key - or null if this object should not be cached.

getEquivalanceKey

@Nullable
public VirtualColumn.EquivalenceKey getEquivalanceKey()

Description copied from interface: VirtualColumn

Returns a key used for "equivalence" comparisons, for checking if some virtual column is equivalent to some other virtual column, regardless of the output name. If this method returns null, it does not participate in equivalence comparisons.

Specified by:

getEquivalanceKey in interface VirtualColumn

See Also:

• VirtualColumns.findEquivalent(VirtualColumns, VirtualColumn)

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