com.hazelcast.org.apache.calcite.adapter.enumerable.AggImplementor Maven / Gradle / Ivy
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* this work for additional information regarding copyright ownership.
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* (the "License"); you may not use this file except in com.hazelcast.com.liance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.com.hazelcast.org.licenses/LICENSE-2.0
*
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package com.hazelcast.org.apache.calcite.adapter.enumerable;
import com.hazelcast.org.apache.calcite.linq4j.tree.Expression;
import java.lang.reflect.Type;
import java.util.List;
/**
* Implements an aggregate function by generating expressions to
* initialize, add to, and get a result from, an accumulator.
*
* @see com.hazelcast.org.apache.calcite.adapter.enumerable.StrictAggImplementor
* @see com.hazelcast.org.apache.calcite.adapter.enumerable.StrictWinAggImplementor
* @see com.hazelcast.org.apache.calcite.adapter.enumerable.RexImpTable.CountImplementor
* @see com.hazelcast.org.apache.calcite.adapter.enumerable.RexImpTable.SumImplementor
*/
public interface AggImplementor {
/**
* Returns the types of the intermediate variables used by the aggregate
* implementation.
*
* For instance, for "concatenate to string" this can be
* {@link java.lang.StringBuilder}.
* Calcite calls this method before all other {@code implement*} methods.
*
* @param info Aggregate context
* @return Types of the intermediate variables used by the aggregate
* implementation
*/
List getStateType(AggContext info);
/**
* Implements reset of the intermediate variables to the initial state.
* {@link 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)));
*
* @param info Aggregate context
* @param reset Reset context
*/
void implementReset(AggContext info, AggResetContext reset);
/**
* Updates intermediate values to account for the newly added value.
* {@link AggResetContext#accumulator()} should be used to reference
* the state variables.
*
* @param info Aggregate context
* @param add Add context
*/
void implementAdd(AggContext info, AggAddContext add);
/**
* 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.
* {@link AggResetContext#accumulator()} should be used to reference
* the state variables.
*
* @param info Aggregate context
* @param result Result context
* @return Expression that is a result of calculating final value of
* the aggregate being implemented
*/
Expression implementResult(AggContext info, AggResultContext result);
}