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

Interface WriterEvents

All Superinterfaces:

WriterPosition

All Known Subinterfaces:

OffsetVectorWriter, UnionWriterImpl.UnionShim

All Known Implementing Classes:

AbstractArrayWriter, AbstractArrayWriter.BaseArrayWriter, AbstractFixedWidthWriter, AbstractFixedWidthWriter.BaseFixedWidthWriter, AbstractFixedWidthWriter.BaseIntWriter, AbstractScalarWriterImpl, AbstractTupleWriter, BaseScalarWriter, BaseVarWidthWriter, BitColumnWriter, DictEntryWriter, DummyArrayWriter, DummyArrayWriter.DummyOffsetVectorWriter, DummyDictWriter, DummyScalarWriter, EmptyListShim, ListWriterImpl, MapWriter, MapWriter.ArrayMapWriter, MapWriter.DummyArrayMapWriter, MapWriter.DummyMapWriter, MapWriter.SingleMapWriter, NullableScalarWriter, ObjectArrayWriter, ObjectDictWriter, OffsetVectorWriterImpl, RepeatedListWriter, RowSetLoaderImpl, RowSetWriterImpl, ScalarArrayWriter, SimpleListShim, TestDummyWriter.RootWriterFixture, UnionVectorShim, UnionWriterImpl

public interface WriterEvents
extends WriterPosition

Internal interface used to control the behavior of writers. Consumers of writers never use this method; it is instead used by the code that implements writers.

Most methods here represents events in a state machine. The top-level writer provides a set of public methods which trigger one or more of these internal events. The events draw some fine distinctions between top-level values and those nested within arrays. See each kind of writer for the details.

The events also ensure symmetry between top-level and nested tuples, especially those nested within an array. That is, an event cannot change meaning depending on whether the tuple is top-level or nested within an array. Instead, the order of calls, or selectively making or not making calls, can change.

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static interface	WriterEvents.ColumnWriterListener Listener (callback) for vector overflow events.
static class	WriterEvents.State Tracks the write state of a tuple or variant to allow applying the correct operations to newly-added columns to synchronize them with the rest of the writers.

Method Summary

Modifier and Type	Method and Description
void	bindIndex(ColumnWriterIndex index) Bind the writer to a writer index.
void	bindListener(WriterEvents.ColumnWriterListener listener) Bind a listener to the underlying vector writer.
void	dump(HierarchicalFormatter format)
void	endArrayValue() End a value.
void	endWrite() End a batch: finalize any vector values.
void	postRollover() The vectors backing this writer rolled over.
void	preRollover() The vectors backing this vector are about to roll over.
void	restartRow() During a writer to a row, rewind the the current index position to restart the row.
void	saveRow() Saves a row.
void	startRow() Start a new row.
void	startWrite() Start a write (batch) operation.

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

lastWriteIndex, rowStartIndex, writeIndex

Method Detail

bindIndex

void bindIndex(ColumnWriterIndex index)

Bind the writer to a writer index.

Parameters:

index - the writer index (top level or nested for arrays)

bindListener

void bindListener(WriterEvents.ColumnWriterListener listener)

Bind a listener to the underlying vector writer. This listener reports on vector events (overflow, growth), and so is called only when the writer is backed by a vector. The listener is ignored (and never called) for dummy (non-projected) columns. If the column is compound (such as for a nullable or repeated column, or for a map), then the writer is bound to the individual components.

Parameters:

listener - the vector event listener to bind

startWrite

void startWrite()

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

startRow

void startRow()

Start a new row. To be called only when a row is not active. To restart a row, call restartRow() instead.

endArrayValue

void endArrayValue()

End a value. Similar to saveRow(), but the save of a value is conditional on saving the row. This version is primarily of use in tuples nested inside arrays: it saves each tuple within the array, advancing to a new position in the array. The update of the array's offset vector based on the cumulative value saves is done when saving the row.

restartRow

void restartRow()

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.

saveRow

void saveRow()

Saves a row. Commits offset vector locations and advances each to the next position. Can be called only when a row is active.

endWrite

void endWrite()

End a batch: finalize any vector values.

preRollover

void preRollover()

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

postRollover

void postRollover()

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.

dump

void dump(HierarchicalFormatter format)