org.apache.flink.table.functions.ImperativeAggregateFunction Maven / Gradle / Ivy
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*
* http://www.apache.org/licenses/LICENSE-2.0
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package org.apache.flink.table.functions;
import org.apache.flink.annotation.PublicEvolving;
import org.apache.flink.api.common.typeinfo.TypeInformation;
import org.apache.flink.table.annotation.DataTypeHint;
import org.apache.flink.table.annotation.FunctionHint;
import org.apache.flink.table.catalog.DataTypeFactory;
/**
* Base class for user-defined {@link AggregateFunction} and {@link TableAggregateFunction}.
*
* This class is used for unified handling of imperative aggregating functions. Concrete
* implementations should extend from {@link AggregateFunction} or {@link TableAggregateFunction}.
*
* @param final result type of the aggregation
* @param intermediate result type during the aggregation
*/
@PublicEvolving
public abstract class ImperativeAggregateFunction extends UserDefinedFunction {
/**
* Creates and initializes the accumulator for this {@link ImperativeAggregateFunction}.
*
* The accumulator is an intermediate data structure that stores the aggregated values until
* a final aggregation result is computed.
*
* @return the accumulator with the initial value
*/
public abstract ACC createAccumulator();
/**
* Returns the {@link TypeInformation} of the {@link ImperativeAggregateFunction}'s result.
*
* @return The {@link TypeInformation} of the {@link ImperativeAggregateFunction}'s result or
* null if the result type should be automatically inferred.
* @deprecated This method uses the old type system and is based on the old reflective
* extraction logic. The method will be removed in future versions and is only called when
* using the deprecated {@code TableEnvironment.registerFunction(...)} method. The new
* reflective extraction logic (possibly enriched with {@link DataTypeHint} and {@link
* FunctionHint}) should be powerful enough to cover most use cases. For advanced users, it
* is possible to override {@link UserDefinedFunction#getTypeInference(DataTypeFactory)}.
*/
@Deprecated
public TypeInformation getResultType() {
return null;
}
/**
* Returns the {@link TypeInformation} of the {@link ImperativeAggregateFunction}'s accumulator.
*
* @return The {@link TypeInformation} of the {@link ImperativeAggregateFunction}'s accumulator
* or null if the accumulator type should be automatically inferred.
* @deprecated This method uses the old type system and is based on the old reflective
* extraction logic. The method will be removed in future versions and is only called when
* using the deprecated {@code TableEnvironment.registerFunction(...)} method. The new
* reflective extraction logic (possibly enriched with {@link DataTypeHint} and {@link
* FunctionHint}) should be powerful enough to cover most use cases. For advanced users, it
* is possible to override {@link UserDefinedFunction#getTypeInference(DataTypeFactory)}.
*/
@Deprecated
public TypeInformation getAccumulatorType() {
return null;
}
}