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

Interface GroupByColumnSelectorStrategy

All Superinterfaces:
ColumnSelectorStrategy
All Known Implementing Classes:
DictionaryBuildingGroupByColumnSelectorStrategy, FixedWidthGroupByColumnSelectorStrategy, KeyMappingMultiValueGroupByColumnSelectorStrategy, KeyMappingMultiValueGroupByColumnSelectorStrategy.DictionaryBuilding, KeyMappingMultiValueGroupByColumnSelectorStrategy.PrebuiltDictionary
public interface GroupByColumnSelectorStrategy extends ColumnSelectorStrategy
Contains a collection of query processing methods for type-specific operations used exclusively by GroupByQueryEngineV2. Each GroupByColumnSelectorStrategy is associated with a single dimension. Strategies may have internal state, such as the dictionary maintained by DictionaryBuildingGroupByColumnSelectorStrategy. Callers should assume that the internal state footprint starts out empty (zero bytes) and is also reset to zero on each call to reset(). Each call to initColumnValues(org.apache.druid.segment.ColumnValueSelector, int, java.lang.Object[]) or writeToKeyBuffer(int, ColumnValueSelector, ByteBuffer) returns the incremental increase in internal state footprint that happened as a result of that particular call.
See Also:

  • Field Details

    • GROUP_BY_MISSING_VALUE

      static final int GROUP_BY_MISSING_VALUE
      Index to indicate the absence of a key in the dictionary
      See Also:

  • Method Details

    • getGroupingKeySizeBytes

      int getGroupingKeySizeBytes()
      Return the size, in bytes, of this dimension's values in the grouping key. For example, a String implementation would return 4, the size of an int.
      Returns:
      size, in bytes, of this dimension's values in the grouping key.

    • processValueFromGroupingKey

      void processValueFromGroupingKey(GroupByColumnSelectorPlus selectorPlus, ByteBuffer key, ResultRow resultRow, int keyBufferPosition)
      Read a value from a grouping key and add it to the group by query result row, using the output name specified in a DimensionSpec. An implementation may choose to not add anything to the result row (e.g., as the String implementation does for empty rows) selectorPlus provides access to: - the keyBufferPosition offset from which to read the value - the dimension value selector - the DimensionSpec for this dimension from the query
      Parameters:
      selectorPlus - dimension info containing the key offset, value selector, and dimension spec
      key - grouping key
      resultRow - result row for the group by query being served
      keyBufferPosition - buffer position for the grouping key, added to support chaining multiple ColumnSelectorStrategy

    • initColumnValues

      @CheckReturnValue int initColumnValues(ColumnValueSelector selector, int columnIndex, Object[] valuess)
      Retrieve a row object from the ColumnValueSelector and put it in valuess at columnIndex.
      Parameters:
      selector - Value selector for a column.
      columnIndex - Index of the column within the row values array
      valuess - Row values array, one index per column
      Returns:
      estimated increase in internal state footprint, in bytes, as a result of this operation. May be zero if memory did not increase as a result of this operation. Will not be negative.

    • initGroupingKeyColumnValue

      void initGroupingKeyColumnValue(int keyBufferPosition, int dimensionIndex, Object rowObj, ByteBuffer keyBuffer, int[] stack)
      Read the first value within a row values object (e. g. IndexedInts, as the value in a dictionary-encoded string column) and write that value to the keyBuffer at keyBufferPosition. If the row size is 0 (e. g. IndexedInts.size()), write GROUP_BY_MISSING_VALUE instead. If the size of the row is > 0, write 1 to stack[] at columnIndex, otherwise write 0.
      Parameters:
      keyBufferPosition - Starting offset for this column's value within the grouping key.
      dimensionIndex - Index of this dimension within the stack array
      rowObj - Row value object for this column
      keyBuffer - grouping key
      stack - array containing the current within-row value index for each column

    • checkRowIndexAndAddValueToGroupingKey

      boolean checkRowIndexAndAddValueToGroupingKey(int keyBufferPosition, Object rowObj, int rowValIdx, ByteBuffer keyBuffer)
      If rowValIdx is less than the size of rowObj (haven't handled all of the row values): First, read the value at rowValIdx from a rowObj and write that value to the keyBuffer at keyBufferPosition. Then return true. This method assumes that the size increase associated with the dictionary building has occurred already when calling initColumnValues(org.apache.druid.segment.ColumnValueSelector, int, java.lang.Object[]) Otherwise, return false.
      Parameters:
      keyBufferPosition - Starting offset for this column's value within the grouping key.
      rowObj - Row value object for this column (e.g., IndexedInts)
      rowValIdx - Index of the current value being grouped on within the row
      keyBuffer - grouping key
      Returns:
      true if rowValIdx invalid input: '<' size of rowObj, false otherwise

    • writeToKeyBuffer

      @CheckReturnValue int writeToKeyBuffer(int keyBufferPosition, ColumnValueSelector selector, ByteBuffer keyBuffer)
      Write a single object from the given selector to the keyBuffer at keyBufferPosition. The reading column must have a single value. The position of the keyBuffer may be modified.
      Parameters:
      keyBufferPosition - starting offset for this column's value within the grouping key
      selector - selector to retrieve row value object from
      keyBuffer - grouping key
      Returns:
      estimated increase in internal state footprint, in bytes, as a result of this operation. May be zero if memory did not increase as a result of this operation. Will not be negative.

    • bufferComparator

      Grouper.BufferComparator bufferComparator(int keyBufferPosition, @Nullable StringComparator stringComparator)
      Return BufferComparator for values written using this strategy when limit is pushed down to segment scan.
      Parameters:
      keyBufferPosition - starting offset for this column's value within the grouping key
      stringComparator - stringComparator from LimitSpec for this column. If this is null, implementations will use the StringComparators.LEXICOGRAPHIC comparator.
      Returns:
      BufferComparator for comparing values written

    • reset

      void reset()
      Reset any internal state held by this selector. After this method is called, any row objects or key objects generated by any methods of this class must be considered unreadable. Calling processValueFromGroupingKey(org.apache.druid.query.groupby.epinephelinae.column.GroupByColumnSelectorPlus, java.nio.ByteBuffer, org.apache.druid.query.groupby.ResultRow, int) on that memory has undefined behavior.