Class CountAggregateDefinition

java.lang.Object
org.apache.derby.impl.sql.compile.CountAggregateDefinition
All Implemented Interfaces:
AggregateDefinition

class CountAggregateDefinition extends Object implements AggregateDefinition
Definition for the COUNT()/COUNT(*) aggregates.
  • Constructor Details

    • CountAggregateDefinition

      public CountAggregateDefinition()
      Niladic constructor. Does nothing. For ease Of use, only.
  • Method Details

    • getAggregator

      public final DataTypeDescriptor getAggregator(DataTypeDescriptor inputType, StringBuffer aggregatorClass)
      Determines the result datatype. We can run count() on anything, and it always returns a INTEGER (java.lang.Integer).
      Specified by:
      getAggregator in interface AggregateDefinition
      Parameters:
      inputType - the input type, either a user type or a java.lang object
      aggregatorClass - output parameter, filled in with the class name that implements com.ibm.db2j.aggregates.Aggregator
      Returns:
      the output Class (null if cannot operate on value expression of this type.
      See Also: