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package com.salesforce.phoenix.iterate;
import java.sql.SQLException;
import java.util.List;
import org.apache.hadoop.hbase.io.ImmutableBytesWritable;
import com.salesforce.phoenix.schema.tuple.Tuple;
import com.salesforce.phoenix.util.SQLCloseables;
/**
*
* Base class for a ResultIterator that does a merge sort on the list of iterators
* provided.
*
* @author jtaylor
* @since 1.2
*/
public abstract class MergeSortResultIterator implements PeekingResultIterator {
protected final ResultIterators resultIterators;
protected final ImmutableBytesWritable tempPtr = new ImmutableBytesWritable();
private List<PeekingResultIterator> iterators;
public MergeSortResultIterator(ResultIterators iterators) {
this.resultIterators = iterators;
}
private List<PeekingResultIterator> getIterators() throws SQLException {
if (iterators == null) {
iterators = resultIterators.getIterators();
}
return iterators;
}
@Override
public void close() throws SQLException {
if (iterators != null) {
SQLCloseables.closeAll(iterators);
}
}
abstract protected int compare(Tuple t1, Tuple t2);
private PeekingResultIterator minIterator() throws SQLException {
List<PeekingResultIterator> iterators = getIterators();
Tuple minResult = null;
PeekingResultIterator minIterator = EMPTY_ITERATOR;
for (int i = iterators.size()-1; i >= 0; i--) {
PeekingResultIterator iterator = iterators.get(i);
Tuple r = iterator.peek();
if (r != null) {
if (minResult == null || compare(r, minResult) < 0) {
minResult = r;
minIterator = iterator;
}
continue;
}
iterator.close();
iterators.remove(i);
}
return minIterator;
}
@Override
public Tuple peek() throws SQLException {
PeekingResultIterator iterator = minIterator();
return iterator.peek();
}
@Override
public Tuple next() throws SQLException {
PeekingResultIterator iterator = minIterator();
return iterator.next();
}
}