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FirstLastValue.java
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FirstLastValue.java
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/*
* JBoss, Home of Professional Open Source.
* See the COPYRIGHT.txt file distributed with this work for information
* regarding copyright ownership. Some portions may be licensed
* to Red Hat, Inc. under one or more contributor license agreements.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
* 02110-1301 USA.
*/
package org.teiid.query.function.aggregate;
import java.util.Arrays;
import java.util.List;
import org.teiid.core.TeiidComponentException;
import org.teiid.core.TeiidProcessingException;
import org.teiid.query.util.CommandContext;
/**
* Just a simple First/Last_value() implementation
*/
public class FirstLastValue extends SingleArgumentAggregateFunction {
private Class<?> type;
private Object value;
private boolean first;
private boolean set;
public void reset() {
value = null;
set = false;
}
public FirstLastValue(Class<?> type, boolean first) {
this.type = type;
this.first = first;
}
@Override
public void addInputDirect(Object input, List<?> tuple,
CommandContext commandContext) throws TeiidProcessingException,
TeiidComponentException {
if (!first) {
value = input;
} else if (!set) {
value = input;
set = true;
}
}
/**
* @see org.teiid.query.function.aggregate.AggregateFunction#getResult(CommandContext)
*/
public Object getResult(CommandContext commandContext) {
return value;
}
@Override
public void getState(List<Object> state) {
state.add(value);
state.add(set);
}
@Override
public int setState(List<?> state, int index) {
value = state.get(index);
set = (Boolean)state.get(index++);
return index++;
}
@Override
public List<? extends Class<?>> getStateTypes() {
return Arrays.asList(type, Boolean.class);
}
@Override
public boolean respectsNull() {
return true;
}
}