Package org.apache.druid.query.groupby.epinephelinae

Class BufferArrayGrouper

java.lang.Object
org.apache.druid.query.groupby.epinephelinae.BufferArrayGrouper
All Implemented Interfaces:
Closeable, AutoCloseable, Grouper<IntKey>, IntGrouper, VectorGrouper
public class BufferArrayGrouper extends Object implements VectorGrouper, IntGrouper
A buffer grouper for array-based aggregation. This grouper stores aggregated values in the buffer using the grouping key as the index.

The buffer is divided into 2 separate regions, i.e., used flag buffer and value buffer. The used flag buffer is a bit set to represent which keys are valid. If a bit of an index is set, that key is valid. Finally, the value buffer is used to store aggregated values. The first index is reserved for GroupByColumnSelectorStrategy.GROUP_BY_MISSING_VALUE.

This grouper is available only when the grouping key is a single indexed dimension of a known cardinality because it directly uses the dimension value as the index for array access. Since the cardinality for the grouping key across different segments cannot be currently retrieved, this grouper can be used only when performing per-segment query execution.

  • Constructor Details

    • BufferArrayGrouper

      public BufferArrayGrouper(com.google.common.base.Supplier<ByteBuffer> bufferSupplier, AggregatorAdapters aggregators, int cardinality)

  • Method Details

    • requiredBufferCapacity

      public static long requiredBufferCapacity(int cardinality, AggregatorFactory[] aggregatorFactories)
      Computes required buffer capacity for a grouping key of the given cardinaltiy and aggregatorFactories. This method assumes that the given cardinality doesn't count nulls. Returns -1 if cardinality + 1 (for null) > Integer.MAX_VALUE. Returns computed required buffer capacity otherwise.

    • init

      public void init()
      Description copied from interface: Grouper
      Initialize the grouper. This method needs to be called before calling Grouper.aggregate(Object) and Grouper.aggregate(Object, int).
      Specified by:
      init in interface Grouper<IntKey>

    • initVectorized

      public void initVectorized(int maxVectorSize)
      Description copied from interface: VectorGrouper
      Initialize the grouper. This method needs to be called before calling VectorGrouper.aggregateVector(org.apache.datasketches.memory.Memory, int, int).
      Specified by:
      initVectorized in interface VectorGrouper

    • isInitialized

      public boolean isInitialized()
      Description copied from interface: Grouper
      Check this grouper is initialized or not.
      Specified by:
      isInitialized in interface Grouper<IntKey>
      Returns:
      true if the grouper is already initialized, otherwise false.

    • aggregateKeyHash

      public AggregateResult aggregateKeyHash(int dimIndex)
      Specified by:
      aggregateKeyHash in interface IntGrouper

    • aggregateVector

      public AggregateResult aggregateVector(org.apache.datasketches.memory.Memory keySpace, int startRow, int endRow)
      Description copied from interface: VectorGrouper
      Aggregate the current vector of rows from "startRow" to "endRow" using the provided keys.
      Specified by:
      aggregateVector in interface VectorGrouper
      Parameters:
      keySpace - array holding keys, chunked into ints. First (endRow - startRow) keys must be valid.
      startRow - row to start at (inclusive).
      endRow - row to end at (exclusive).
      Returns:
      result that indicates how many keys were aggregated (may be partial due to resource limits)

    • reset

      public void reset()
      Description copied from interface: VectorGrouper
      Reset the grouper to its initial state.
      Specified by:
      reset in interface Grouper<IntKey>
      Specified by:
      reset in interface VectorGrouper

    • hashFunction

      public IntGrouper.IntGrouperHashFunction hashFunction()
      Specified by:
      hashFunction in interface Grouper<IntKey>
      Specified by:
      hashFunction in interface IntGrouper

    • close

      public void close()
      Description copied from interface: VectorGrouper
      Close the grouper and release associated resources.
      Specified by:
      close in interface AutoCloseable
      Specified by:
      close in interface Closeable
      Specified by:
      close in interface Grouper<IntKey>
      Specified by:
      close in interface VectorGrouper

    • iterator

      public CloseableIterator<Grouper.Entry<MemoryPointer>> iterator()
      Description copied from interface: VectorGrouper
      Iterate through entry buckets. Each bucket's key is a MemoryPointer object in native byte order.

      After you are done with the iterator returned by this method, you should either call VectorGrouper.close() (if you are done with the VectorGrouper) or VectorGrouper.reset() (if you want to reuse it).

      Callers must process and discard the returned Grouper.Entrys immediately, because objects may be reused.

      Specified by:
      iterator in interface VectorGrouper
      Returns:
      entry iterator

    • iterator

      public CloseableIterator<Grouper.Entry<IntKey>> iterator(boolean sorted)
      Description copied from interface: Grouper
      Iterate through entries.

      Some implementations allow writes even after this method is called. After you are done with the iterator returned by this method, you should either call Grouper.close() (if you are done with the Grouper) or Grouper.reset() (if you want to reuse it). Some implementations allow calling Grouper.iterator(boolean) again if you want another iterator. But, this method must not be called by multiple threads concurrently.

      If "sorted" is true then the iterator will return sorted results. It will use KeyType's natural ordering on deserialized objects, and will use the Grouper.KeySerde.bufferComparator() on serialized objects. Woe be unto you if these comparators are not equivalent.

      Callers must process and discard the returned Grouper.Entrys immediately because some implementations can reuse the key objects.

      Specified by:
      iterator in interface Grouper<IntKey>
      Parameters:
      sorted - return sorted results
      Returns:
      entry iterator