org.apache.drill.exec.vector.accessor.writer

Class AbstractFixedWidthWriter

java.lang.Object

org.apache.drill.exec.vector.accessor.writer.AbstractScalarWriter

org.apache.drill.exec.vector.accessor.writer.AbstractScalarWriterImpl

org.apache.drill.exec.vector.accessor.writer.BaseScalarWriter

org.apache.drill.exec.vector.accessor.writer.AbstractFixedWidthWriter

All Implemented Interfaces:

ColumnWriter, ScalarWriter, ValueWriter, WriterEvents, WriterPosition

Direct Known Subclasses:

AbstractFixedWidthWriter.BaseFixedWidthWriter, BitColumnWriter, OffsetVectorWriterImpl

public abstract class AbstractFixedWidthWriter
extends BaseScalarWriter

Base class for writers for fixed-width vectors. Handles common tasks, leaving the generated code to handle only type-specific operations.

Fixed-width writers provide default values for empty (unused) slots. Suppose a client writes to slot 0, skips a few rows, then writes to slot 5. We could leave the intermediate values unwritten. But, since Drill reuses buffers, the slots may contain garbage. Instead, we implement "fill empties" logic. When we write to slot 5, we notice that the last slot written was 0, and we fill in slots 1, 2, 3 and 4 with values.

The fill value defaults to 0, and is defined as a block of zero-bytes (at least) the same length as each data value. Derived classes also allow setting a default value. In this case, the default value is encoded into a byte array, and that array is copied to each slot as the fill value.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	AbstractFixedWidthWriter.BaseFixedWidthWriter
static class	AbstractFixedWidthWriter.BaseIntWriter Base class for writers that use the Java int type as their native type.

Nested classes/interfaces inherited from class org.apache.drill.exec.vector.accessor.writer.AbstractScalarWriterImpl

AbstractScalarWriterImpl.ScalarObjectWriter

Nested classes/interfaces inherited from interface org.apache.drill.exec.vector.accessor.writer.WriterEvents

WriterEvents.ColumnWriterListener, WriterEvents.State

Field Summary

Fields

Modifier and Type	Field and Description
protected int	lastWriteIndex The largest position to which the writer has written data.

Fields inherited from class org.apache.drill.exec.vector.accessor.writer.BaseScalarWriter

capacity, drillBuf, emptyValue, listener, MIN_BUFFER_SIZE

Fields inherited from class org.apache.drill.exec.vector.accessor.writer.AbstractScalarWriterImpl

schema, vectorIndex

Constructor Summary

Constructors

Constructor and Description
AbstractFixedWidthWriter()

Method Summary

Modifier and Type	Method and Description
void	dump(HierarchicalFormatter format)
void	endWrite() End a batch: finalize any vector values.
protected abstract void	fillEmpties(int writeIndex)
int	lastWriteIndex() Return the last write position in the vector.
protected void	mandatoryResize(int writeIndex)
void	postRollover() The vectors backing this writer rolled over.
void	preRollover() The vectors backing this vector are about to roll over.
protected int	resize(int writeIndex)
void	restartRow() During a writer to a row, rewind the the current index position to restart the row.
protected void	setBuffer() All change of buffer comes through this function to allow capturing the buffer address and capacity.
void	setLastWriteIndex(int index) For internal use only to update the write position on those very rare occasions in which the vector is written to outside of this writer framework.
void	setValueCount(int valueCount)
void	skipNulls()
void	startWrite() Start a write (batch) operation.
abstract int	width()

Methods inherited from class org.apache.drill.exec.vector.accessor.writer.BaseScalarWriter

appendBytes, bindListener, bindSchema, canExpand, nullable, overflowed, realloc, setBoolean, setBytes, setDate, setDecimal, setDouble, setFloat, setInt, setLong, setNull, setPeriod, setString, setTime, setTimestamp

Methods inherited from class org.apache.drill.exec.vector.accessor.writer.AbstractScalarWriterImpl

bindIndex, endArrayValue, isProjected, rowStartIndex, saveRow, schema, startRow, type, vector, writeIndex

Methods inherited from class org.apache.drill.exec.vector.accessor.writer.AbstractScalarWriter

conversionError, extendedType, setObject, toString

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.drill.exec.vector.accessor.ScalarWriter

setDefaultValue, valueType

Methods inherited from interface org.apache.drill.exec.vector.accessor.ColumnWriter

copy

Methods inherited from interface org.apache.drill.exec.vector.accessor.ValueWriter

setValue

Field Detail

lastWriteIndex

protected int lastWriteIndex

The largest position to which the writer has written data. Used to allow "fill-empties" (AKA "back-fill") of missing values one each value write and at the end of a batch. Note that this is the position of the last write, not the next write position. Starts at -1 (no last write).

Constructor Detail

AbstractFixedWidthWriter

public AbstractFixedWidthWriter()

Method Detail

startWrite

public void startWrite()

Description copied from interface: WriterEvents

Start a write (batch) operation. Performs any vector initialization required at the start of a batch (especially for offset vectors.)

Specified by:

startWrite in interface WriterEvents

Overrides:

startWrite in class AbstractScalarWriterImpl

width

public abstract int width()

setBuffer

protected final void setBuffer()

Description copied from class: BaseScalarWriter

All change of buffer comes through this function to allow capturing the buffer address and capacity. Only two ways to set the buffer: by binding to a vector in bindVector(), or by resizing the vector in prepareWrite().

Specified by:

setBuffer in class BaseScalarWriter

mandatoryResize

protected final void mandatoryResize(int writeIndex)

resize

protected final int resize(int writeIndex)

lastWriteIndex

public int lastWriteIndex()

Description copied from interface: WriterPosition

Return the last write position in the vector. This may be the same as the writer index position (if the vector was written at that point), or an earlier point. In either case, this value points to the last valid value in the vector.

Returns:

index of the last valid value in the vector

setLastWriteIndex

public void setLastWriteIndex(int index)

For internal use only to update the write position on those very rare occasions in which the vector is written to outside of this writer framework. Not to be called by application code!

Parameters:

index - new last write index

skipNulls

public void skipNulls()

Specified by:

skipNulls in class BaseScalarWriter

restartRow

public void restartRow()

Description copied from interface: WriterEvents

During a writer to a row, rewind the the current index position to restart the row. Done when abandoning the current row, such as when filtering out a row at read time.

preRollover

public void preRollover()

Description copied from interface: WriterEvents

The vectors backing this vector are about to roll over. Finish the current batch up to, but not including, the current row.

postRollover

public void postRollover()

Description copied from interface: WriterEvents

The vectors backing this writer rolled over. This means that data for the current row has been rolled over into a new vector. Offsets and indexes should be shifted based on the understanding that data for the current row now resides at the start of a new vector instead of its previous location elsewhere in an old vector.

endWrite

public void endWrite()

Description copied from interface: WriterEvents

End a batch: finalize any vector values.

fillEmpties

protected abstract void fillEmpties(int writeIndex)

setValueCount

public void setValueCount(int valueCount)

dump

public void dump(HierarchicalFormatter format)

Specified by:

dump in interface WriterEvents

Overrides:

dump in class BaseScalarWriter