org.apache.druid.frame.segment.row

Class FrameColumnSelectorFactory

java.lang.Object

org.apache.druid.frame.segment.row.FrameColumnSelectorFactory

All Implemented Interfaces:

Expr.InputBindingInspector, ColumnInspector, ColumnSelectorFactory, RowIdSupplier

public class FrameColumnSelectorFactory
extends Object
implements ColumnSelectorFactory, RowIdSupplier

Field Summary

Fields

Modifier and Type	Field and Description
static String	ROW_MEMORY_COLUMN Name of the virtual column that contains MemoryRange for direct access to row memory.
static String	ROW_SIGNATURE_COLUMN Name of the virtual column that contains the RowSignature of frames from this ColumnSelectorFactory.

Fields inherited from interface org.apache.druid.segment.RowIdSupplier

INIT

Constructor Summary

Constructors

Constructor and Description
FrameColumnSelectorFactory(Frame frame, RowSignature frameSignature, List<FieldReader> fieldReaders, ReadableFrameRowPointer rowPointer)

Method Summary

Modifier and Type	Method and Description
ColumnCapabilities	getColumnCapabilities(String column) Returns capabilities of a particular column, if known.
long	getRowId() Returns a number that uniquely identifies the current position of some underlying cursor.
RowIdSupplier	getRowIdSupplier() Returns a RowIdSupplier that allows callers to detect whether the selectors returned by this factory have moved or not.
ColumnValueSelector	makeColumnValueSelector(String columnName) Returns ColumnValueSelector corresponding to the given column name, or NilColumnValueSelector if the column with such name is absent.
DimensionSelector	makeDimensionSelector(DimensionSpec dimensionSpec)

Methods inherited from class java.lang.Object

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

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

getColumnCapabilitiesWithDefault, getType

Methods inherited from interface org.apache.druid.math.expr.Expr.InputBindingInspector

areNumeric, areNumeric, areSameTypes, areSameTypes, areScalar, areScalar, canVectorize, canVectorize

Field Detail

ROW_SIGNATURE_COLUMN

public static final String ROW_SIGNATURE_COLUMN

Name of the virtual column that contains the RowSignature of frames from this ColumnSelectorFactory. This is necessary because callers need it to verify that ROW_MEMORY_COLUMN is usable, but the interface does not provide a natural way to retrieve the underlying signature. Guaranteed not to appear in the frame itself due to FrameWriterUtils.findDisallowedFieldNames(org.apache.druid.segment.column.RowSignature) checks.

See Also:

Constant Field Values

ROW_MEMORY_COLUMN

public static final String ROW_MEMORY_COLUMN

Name of the virtual column that contains MemoryRange for direct access to row memory. Guaranteed not to appear in the frame itself due to FrameWriterUtils.findDisallowedFieldNames(org.apache.druid.segment.column.RowSignature) checks.

See Also:

Constant Field Values

Constructor Detail

FrameColumnSelectorFactory

public FrameColumnSelectorFactory(Frame frame,
                                  RowSignature frameSignature,
                                  List<FieldReader> fieldReaders,
                                  ReadableFrameRowPointer rowPointer)

Method Detail

makeDimensionSelector

public DimensionSelector makeDimensionSelector(DimensionSpec dimensionSpec)

Specified by:

makeDimensionSelector in interface ColumnSelectorFactory

makeColumnValueSelector

public ColumnValueSelector makeColumnValueSelector(String columnName)

Description copied from interface: ColumnSelectorFactory

Returns ColumnValueSelector corresponding to the given column name, or NilColumnValueSelector if the column with such name is absent.

Specified by:

makeColumnValueSelector in interface ColumnSelectorFactory

getRowIdSupplier

@Nullable
public RowIdSupplier getRowIdSupplier()

Description copied from interface: ColumnSelectorFactory

Returns a RowIdSupplier that allows callers to detect whether the selectors returned by this factory have moved or not. Useful for selectors that wrap other selectors, such as virtual columns, as it allows them to cache their outputs.

Specified by:

getRowIdSupplier in interface ColumnSelectorFactory

getRowId

public long getRowId()

Description copied from interface: RowIdSupplier

Returns a number that uniquely identifies the current position of some underlying cursor. This is useful for caching: it is safe to assume nothing has changed in the selector as long as the row ID stays the same. Row IDs do not need to be contiguous or monotonic. They need not have any meaning. In particular: they may not be row *numbers* (row number 0 may have any arbitrary row ID). Valid row IDs are always nonnegative.

Specified by:

getRowId in interface RowIdSupplier

getColumnCapabilities

@Nullable
public ColumnCapabilities getColumnCapabilities(String column)

Description copied from interface: ColumnSelectorFactory

Returns capabilities of a particular column, if known. May be null if the column doesn't exist, or if the column does exist but the capabilities are unknown. The latter is possible with dynamically discovered columns.

Specified by:

getColumnCapabilities in interface ColumnInspector

Specified by:

getColumnCapabilities in interface ColumnSelectorFactory

Parameters:

column - column name

Returns:

capabilities, or null