WritableColumnVector-spark技术分享

WritableColumnVector

WritableColumnVector is the contract for…FIXME



package org.apache.spark.sql.execution.vectorized;

abstract class WritableColumnVector extends ColumnVector {
  // only required methods that have no implementation
  // the others follow
  public abstract int getDictId(int rowId);
  protected abstract void reserveInternal(int capacity);
  public abstract void putNotNull(int rowId);
  public abstract void putNull(int rowId);
  public abstract void putNulls(int rowId, int count);
  public abstract void putNotNulls(int rowId, int count);
  // other type-specific puts
  protected abstract WritableColumnVector reserveNewColumn(int capacity, DataType type);
}

package org.apache.spark.sql.execution.vectorized;

abstract class WritableColumnVector extends ColumnVector {

// only required methods that have no implementation

// the others follow

public abstract int getDictId(int rowId);

protected abstract void reserveInternal(int capacity);

public abstract void putNotNull(int rowId);

public abstract void putNull(int rowId);

public abstract void putNulls(int rowId, int count);

public abstract void putNotNulls(int rowId, int count);

// other type-specific puts

protected abstract WritableColumnVector reserveNewColumn(int capacity, DataType type);

}

Table 1. (Subset of) WritableColumnVector Contract
Method	Description
`reserveInternal`	Used when: OnHeapColumnVector and `OffHeapColumnVector` are created `WritableColumnVector` is requested to reserve
`reserveNewColumn`	Used when `WritableColumnVector` is created and requested to reserveDictionaryIds

Table 2. WritableColumnVectors
WritableColumnVector	Description
OffHeapColumnVector
OnHeapColumnVector

`reset` Method



void reset()

void reset()

reset…FIXME

Note	`reset` is used when…FIXME

`reserve` Method



void reserve(int requiredCapacity)

void reserve(int requiredCapacity)

reserve…FIXME

Note	`reserve` is used when…FIXME

`reserveDictionaryIds` Method



WritableColumnVector reserveDictionaryIds(int capacity)

WritableColumnVector reserveDictionaryIds(int capacity)

reserveDictionaryIds…FIXME

Note	`reserveDictionaryIds` is used when…FIXME

Creating WritableColumnVector Instance

WritableColumnVector takes the following when created:

Number of elements to hold in a vector (aka capacity)
Data type of the elements stored

WritableColumnVector initializes the internal registries and counters.

WritableColumnVector…FIXME

Note	`WritableColumnVector` is a Java abstract class and cannot be created directly.

WritableColumnVector