Maksim Zhuravkov created IGNITE-23335:
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Summary: Sql. Do not store aggregation state in Accumulator
Key: IGNITE-23335
URL: https://issues.apache.org/jira/browse/IGNITE-23335
Project: Ignite
Issue Type: Improvement
Components: sql
Reporter: Maksim Zhuravkov
`Accumulator` stores aggregation state, we should extract this state making
`Accumulator` pure functions.
Current accumulator (except methods that return result types).
{code:java}
public interface Accumulator {
void add(Object... args);
Object end();
{code}
DoubleAvg example:
{code:java}
public static class DoubleAvg implements Accumulator {
public static final Supplier<Accumulator> FACTORY = DoubleAvg::new;
private double sum;
private long cnt;
/** {@inheritDoc} */
@Override
public void add(Object... args) {
Double in = (Double) args[0];
if (in == null) {
return;
}
sum += in;
cnt++;
}
/** {@inheritDoc} */
@Override
public Object end() {
return cnt > 0 ? sum / cnt : null;
}
{code}
{code:java}
public interface Accumulator {
void init(AggregateState state);
void update(AggregateState state, arguments);
void end(AggregateState state);
{code}
Aggregate should be stored in aggregate operators (HashAggregateNode, ). We
should also move DistinctAccumulator (AVG(DISTINCT x) to HashAggregateNode
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