Package org.apache.calcite.adapter.enumerable

Interface AggImplementor

All Known Subinterfaces:
WinAggImplementor
All Known Implementing Classes:
RexImpTable.LagImplementor, RexImpTable.LeadImplementor, RexImpTable.UserDefinedAggReflectiveImplementor, StrictAggImplementor, StrictWinAggImplementor
public interface AggImplementor
Implements an aggregate function by generating expressions to initialize, add to, and get a result from, an accumulator.
See Also:

  • Method Details

    • getStateType

      List<Type> getStateType(AggContext info)
      Returns the types of the intermediate variables used by the aggregate implementation.

      For instance, for "concatenate to string" this can be StringBuilder. Calcite calls this method before all other implement* methods.

      Parameters:
      info - Aggregate context
      Returns:
      Types of the intermediate variables used by the aggregate implementation

    • implementReset

      void implementReset(AggContext info, AggResetContext reset)
      Implements reset of the intermediate variables to the initial state. AggResetContext.accumulator() should be used to reference the state variables. For instance, to zero the count, use the following code:
      reset.currentBlock().add(
      Expressions.statement(
      Expressions.assign(reset.accumulator().get(0),
      Expressions.constant(0)));
      Parameters:
      info - Aggregate context
      reset - Reset context

    • implementAdd

      void implementAdd(AggContext info, AggAddContext add)
      Updates intermediate values to account for the newly added value. AggResetContext.accumulator() should be used to reference the state variables.
      Parameters:
      info - Aggregate context
      add - Add context

    • implementResult

      Expression implementResult(AggContext info, AggResultContext result)
      Calculates the resulting value based on the intermediate variables. Note: this method must NOT destroy the intermediate variables as calcite might reuse the state when calculating sliding aggregates. AggResetContext.accumulator() should be used to reference the state variables.
      Parameters:
      info - Aggregate context
      result - Result context
      Returns:
      Expression that is a result of calculating final value of the aggregate being implemented