org.apache.druid.frame.field

Class StringFieldReader

java.lang.Object

org.apache.druid.frame.field.StringFieldReader

All Implemented Interfaces:

FieldReader

public class StringFieldReader
extends Object
implements FieldReader

Reads fields written by StringFieldWriter or StringArrayFieldWriter. Strings are written in UTF8 and terminated by StringFieldWriter.VALUE_TERMINATOR. Note that this byte appears in valid UTF8 encodings if and only if the string contains a NUL (char 0). Therefore, this field writer cannot write out strings containing NUL characters. Rows are terminated by StringFieldWriter.ROW_TERMINATOR. Nulls are stored as StringFieldWriter.NULL_BYTE. All other strings are prepended by StringFieldWriter.NOT_NULL_BYTE byte to differentiate them from nulls. This encoding allows the encoded data to be compared as bytes in a way that matches the behavior of StringDimensionHandler.DIMENSION_SELECTOR_COMPARATOR, except null and empty list are not considered equal.

Method Summary

Modifier and Type	Method and Description
boolean	isComparable() Whether this field is comparable.
boolean	isNull(org.apache.datasketches.memory.Memory memory, long position) Whether the provided memory position points to a null value.
ColumnValueSelector<?>	makeColumnValueSelector(org.apache.datasketches.memory.Memory memory, ReadableFieldPointer fieldPointer) Create a ColumnValueSelector backed by some memory and a moveable pointer.
DimensionSelector	makeDimensionSelector(org.apache.datasketches.memory.Memory memory, ReadableFieldPointer fieldPointer, ExtractionFn extractionFn) Create a DimensionSelector backed by some memory and a moveable pointer.

Methods inherited from class java.lang.Object

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

Method Detail

makeColumnValueSelector

public ColumnValueSelector<?> makeColumnValueSelector(org.apache.datasketches.memory.Memory memory,
                                                      ReadableFieldPointer fieldPointer)

Description copied from interface: FieldReader

Create a ColumnValueSelector backed by some memory and a moveable pointer.

Specified by:

makeColumnValueSelector in interface FieldReader

makeDimensionSelector

public DimensionSelector makeDimensionSelector(org.apache.datasketches.memory.Memory memory,
                                               ReadableFieldPointer fieldPointer,
                                               @Nullable
                                               ExtractionFn extractionFn)

Description copied from interface: FieldReader

Create a DimensionSelector backed by some memory and a moveable pointer.

Specified by:

makeDimensionSelector in interface FieldReader

isNull

public boolean isNull(org.apache.datasketches.memory.Memory memory,
                      long position)

Description copied from interface: FieldReader

Whether the provided memory position points to a null value.

Specified by:

isNull in interface FieldReader

isComparable

public boolean isComparable()

Description copied from interface: FieldReader

Whether this field is comparable. Comparable fields can be compared as unsigned bytes.

Specified by:

isComparable in interface FieldReader