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

Class DummyArrayWriter

java.lang.Object
org.apache.drill.exec.vector.accessor.writer.AbstractArrayWriter
org.apache.drill.exec.vector.accessor.writer.dummy.DummyArrayWriter
All Implemented Interfaces:
ArrayWriter, ColumnWriter, WriterEvents, WriterPosition
Direct Known Subclasses:
DummyDictWriter
public class DummyArrayWriter extends AbstractArrayWriter
Dummy scalar array writer that allows a client to write values into the array, but discards all of them. Provides no implementations of any methods, all are simply ignored.

Experience may suggest that some methods must return non-dummy values, such as the number of items in the array. That can be added as needed.

  • Field Details

  • Constructor Details

  • Method Details

    • save

      public void save()
      Description copied from interface: ArrayWriter
      When the array contains a tuple or an array, call save() after each array value. Not necessary when writing scalars; each set operation calls save automatically.

    • setObject

      public void setObject(Object array)
      Description copied from interface: ColumnWriter
      Generic technique to write data as a generic Java object. The type of the object must match the target writer. Primarily for testing.
      • Scalar: The type of the Java object must match the type of the target vector. String or byte[] can be used for Varchar vectors.
      • Array: Write the array given an array of values. The object must be a Java array. The type of the array must match the type of element in the repeated vector. That is, if the vector is a Repeated Int, provide an int[] array.
      • Tuple (map or row): The Java object must be an array of objects in which the members of the array have a 1:1 correspondence with the members of the tuple in the order defined by the writer metadata. That is, if the map is (Int, Varchar), provide a Object[] array like this: {10, "fred"}.
      • Union: Uses the Java object type to determine the type of the backing vector. Creates a vector of the required type if needed.
      Parameters:
      array - value to write to the vector. The Java type of the object indicates the Drill storage type

    • 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.)

    • startRow

      public void startRow()
      Description copied from interface: WriterEvents
      Start a new row. To be called only when a row is not active. To restart a row, call WriterEvents.restartRow() instead.

    • endArrayValue

      public void endArrayValue()
      Description copied from interface: WriterEvents
      End a value. Similar to WriterEvents.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

      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.

    • saveRow

      public void saveRow()
      Description copied from interface: WriterEvents
      Saves a row. Commits offset vector locations and advances each to the next position. Can be called only when a row is active.

    • endWrite

      public void endWrite()
      Description copied from interface: WriterEvents
      End a batch: finalize any vector values.

    • 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.

    • 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.
      Specified by:
      lastWriteIndex in interface WriterPosition
      Overrides:
      lastWriteIndex in class AbstractArrayWriter
      Returns:
      index of the last valid value in the vector

    • bindIndex

      public void bindIndex(ColumnWriterIndex index)
      Description copied from interface: WriterEvents
      Bind the writer to a writer index.
      Parameters:
      index - the writer index (top level or nested for arrays)

    • isProjected

      public boolean isProjected()
      Description copied from interface: ColumnWriter
      Whether this writer is projected (is backed by a materialized vector), or is unprojected (is just a dummy writer.) In most cases, clients can ignore whether the column is projected and just write to the writer. This flag handles those special cases where it is helpful to know if the column is projected or not.
      Specified by:
      isProjected in interface ColumnWriter
      Overrides:
      isProjected in class AbstractArrayWriter

    • copy

      public void copy(ColumnReader from)
      Description copied from interface: ColumnWriter
      Copy a single value from the given reader, which must be of the same type as this writer.
      Specified by:
      copy in interface ColumnWriter
      Overrides:
      copy in class AbstractArrayWriter
      Parameters:
      from - reader to provide the data