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c

org.apache.spark.sql.execution.aggregate

VectorizedHashMapGenerator

class VectorizedHashMapGenerator extends HashMapGenerator

This is a helper class to generate an append-only vectorized hash map that can act as a 'cache' for extremely fast key-value lookups while evaluating aggregates (and fall back to the BytesToBytesMap if a given key isn't found). This is 'codegened' in HashAggregate to speed up aggregates w/ key.

It is backed by a power-of-2-sized array for index lookups and a columnar batch that stores the key-value pairs. The index lookups in the array rely on linear probing (with a small number of maximum tries) and use an inexpensive hash function which makes it really efficient for a majority of lookups. However, using linear probing and an inexpensive hash function also makes it less robust as compared to the BytesToBytesMap (especially for a large number of keys or even for certain distribution of keys) and requires us to fall back on the latter for correctness. We also use a secondary columnar batch that logically projects over the original columnar batch and is equivalent to the BytesToBytesMap aggregate buffer.

NOTE: This vectorized hash map currently doesn't support nullable keys and falls back to the BytesToBytesMap to store them.

Linear Supertypes
HashMapGenerator, AnyRef, Any
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  1. VectorizedHashMapGenerator
  2. HashMapGenerator
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Instance Constructors

  1. new VectorizedHashMapGenerator(ctx: CodegenContext, aggregateExpressions: Seq[AggregateExpression], generatedClassName: String, groupingKeySchema: StructType, bufferSchema: StructType, bitMaxCapacity: Int)

Type Members

  1. case class Buffer(dataType: DataType, name: String) extends Product with Serializable
    Definition Classes
    HashMapGenerator

Value Members

  1. final def !=(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  2. final def ##(): Int
    Definition Classes
    AnyRef → Any
  3. final def ==(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  4. final def asInstanceOf[T0]: T0
    Definition Classes
    Any
  5. val buffVars: Seq[ExprCode]
    Definition Classes
    HashMapGenerator
  6. val bufferValues: Seq[Buffer]
    Definition Classes
    HashMapGenerator
  7. def clone(): AnyRef
    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( ... ) @native()
  8. final def eq(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  9. def equals(arg0: Any): Boolean
    Definition Classes
    AnyRef → Any
  10. def finalize(): Unit
    Attributes
    protected[lang]
    Definition Classes
    AnyRef
    Annotations
    @throws( classOf[java.lang.Throwable] )
  11. final def genComputeHash(ctx: CodegenContext, input: String, dataType: DataType, result: String): String
    Attributes
    protected
    Definition Classes
    HashMapGenerator
  12. def generate(): String
    Definition Classes
    HashMapGenerator
  13. final def generateClose(): String
    Attributes
    protected
    Definition Classes
    HashMapGenerator
  14. def generateEquals(): String

    Generates a method that returns true if the group-by keys exist at a given index in the associated org.apache.spark.sql.execution.vectorized.OnHeapColumnVector.

    Generates a method that returns true if the group-by keys exist at a given index in the associated org.apache.spark.sql.execution.vectorized.OnHeapColumnVector. For instance, if we have 2 long group-by keys, the generated function would be of the form:

    private boolean equals(int idx, long agg_key, long agg_key1) {
  return vectors[0].getLong(buckets[idx]) == agg_key &&
    vectors[1].getLong(buckets[idx]) == agg_key1;
}
    Attributes
    protected
    Definition Classes
    VectorizedHashMapGenerator → HashMapGenerator
  15. def generateFindOrInsert(): String

    Generates a method that returns a org.apache.spark.sql.execution.vectorized.MutableColumnarRow which keeps track of the aggregate value(s) for a given set of keys.

    Generates a method that returns a org.apache.spark.sql.execution.vectorized.MutableColumnarRow which keeps track of the aggregate value(s) for a given set of keys. If the corresponding row doesn't exist, the generated method adds the corresponding row in the associated org.apache.spark.sql.execution.vectorized.OnHeapColumnVector. For instance, if we have 2 long group-by keys, the generated function would be of the form:

    public MutableColumnarRow findOrInsert(long agg_key, long agg_key1) {
  long h = hash(agg_key, agg_key1);
  int step = 0;
  int idx = (int) h & (numBuckets - 1);
  while (step < maxSteps) {
    // Return bucket index if it's either an empty slot or already contains the key
    if (buckets[idx] == -1) {
      if (numRows < capacity) {
        vectors[0].putLong(numRows, agg_key);
        vectors[1].putLong(numRows, agg_key1);
        vectors[2].putLong(numRows, 0);
        buckets[idx] = numRows++;
        aggBufferRow.rowId = numRows;
        return aggBufferRow;
      } else {
        // No more space
        return null;
      }
    } else if (equals(idx, agg_key, agg_key1)) {
      aggBufferRow.rowId = buckets[idx];
      return aggBufferRow;
    }
    idx = (idx + 1) & (numBuckets - 1);
    step++;
  }
  // Didn't find it
  return null;
}
    Attributes
    protected
    Definition Classes
    VectorizedHashMapGenerator → HashMapGenerator
  16. final def generateHashFunction(): String

    Generates a method that computes a hash by currently xor-ing all individual group-by keys.

    Generates a method that computes a hash by currently xor-ing all individual group-by keys. For instance, if we have 2 long group-by keys, the generated function would be of the form:

    private long hash(long agg_key, long agg_key1) {
  return agg_key ^ agg_key1;
  }
    Attributes
    protected
    Definition Classes
    HashMapGenerator
  17. def generateRowIterator(): String
    Attributes
    protected
    Definition Classes
    VectorizedHashMapGenerator → HashMapGenerator
  18. final def getClass(): Class[_]
    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  19. val groupingKeySignature: String
    Definition Classes
    HashMapGenerator
  20. val groupingKeys: Seq[Buffer]
    Definition Classes
    HashMapGenerator
  21. def hashCode(): Int
    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  22. def initializeAggregateHashMap(): String
    Attributes
    protected
    Definition Classes
    VectorizedHashMapGenerator → HashMapGenerator
  23. final def isInstanceOf[T0]: Boolean
    Definition Classes
    Any
  24. final def ne(arg0: AnyRef): Boolean
    Definition Classes
    AnyRef
  25. final def notify(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native()
  26. final def notifyAll(): Unit
    Definition Classes
    AnyRef
    Annotations
    @native()
  27. final def synchronized[T0](arg0: ⇒ T0): T0
    Definition Classes
    AnyRef
  28. def toString(): String
    Definition Classes
    AnyRef → Any
  29. final def wait(): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  30. final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... )
  31. final def wait(arg0: Long): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws( ... ) @native()

Inherited from HashMapGenerator

Inherited from AnyRef

Inherited from Any

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