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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.expression.Expression;
import com.salesforce.phoenix.schema.PDataType;
import com.salesforce.phoenix.schema.tuple.Tuple;
/**
*
* Result scanner that filters out rows based on the results of a boolean
* expression (i.e. filters out if {@link com.salesforce.phoenix.expression.Expression#evaluate(Tuple, ImmutableBytesWritable)}
* returns false or the ptr contains a FALSE value}). May not be used where
* the delegate provided is an {@link com.salesforce.phoenix.iterate.AggregatingResultIterator}.
* For these, the {@link com.salesforce.phoenix.iterate.FilterAggregatingResultIterator} should be used.
*
* @author jtaylor
* @since 0.1
*/
public class FilterResultIterator extends LookAheadResultIterator {
private final ResultIterator delegate;
private final Expression expression;
private final ImmutableBytesWritable ptr = new ImmutableBytesWritable();
public FilterResultIterator(ResultIterator delegate, Expression expression) {
if (delegate instanceof AggregatingResultIterator) {
throw new IllegalArgumentException("FilterResultScanner may not be used with an aggregate delegate. Use phoenix.iterate.FilterAggregateResultScanner instead");
}
this.delegate = delegate;
this.expression = expression;
if (expression.getDataType() != PDataType.BOOLEAN) {
throw new IllegalArgumentException("FilterResultIterator requires a boolean expression, but got " + expression);
}
}
@Override
protected Tuple advance() throws SQLException {
Tuple next;
do {
next = delegate.next();
} while (next != null && expression.evaluate(next, ptr) && Boolean.FALSE.equals(expression.getDataType().toObject(ptr)));
return next;
}
@Override
public void close() throws SQLException {
delegate.close();
}
@Override
public void explain(List<String> planSteps) {
delegate.explain(planSteps);
planSteps.add("CLIENT FILTER BY " + expression.toString());
}
}