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package com.salesforce.phoenix.iterate;

import static com.salesforce.phoenix.query.QueryConstants.*;

import java.sql.SQLException;

import com.salesforce.phoenix.expression.aggregator.Aggregators;
import com.salesforce.phoenix.schema.tuple.SingleKeyValueTuple;
import com.salesforce.phoenix.schema.tuple.Tuple;
import com.salesforce.phoenix.util.KeyValueUtil;


public class UngroupedAggregatingResultIterator extends GroupedAggregatingResultIterator {
    private boolean hasRows = false;

    public UngroupedAggregatingResultIterator( PeekingResultIterator resultIterator, Aggregators aggregators) {
        super(resultIterator, aggregators);
    }
    
    @Override
    public Tuple next() throws SQLException {
        Tuple result = super.next();
        // Ensure ungrouped aggregregation always returns a row, even if the underlying iterator doesn't.
        if (result == null && !hasRows) {
            // Generate value using unused ClientAggregators
            byte[] value = aggregators.toBytes(aggregators.getAggregators());
            result = new SingleKeyValueTuple(
                    KeyValueUtil.newKeyValue(UNGROUPED_AGG_ROW_KEY, 
                            SINGLE_COLUMN_FAMILY, 
                            SINGLE_COLUMN, 
                            AGG_TIMESTAMP, 
                            value));
        }
        hasRows = true;
        return result;
    }
}
