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/*
* Copyright 2006-2012 Amazon Technologies, Inc. or its affiliates.
* Amazon, Amazon.com and Carbonado are trademarks or registered trademarks
* of Amazon Technologies, Inc. or its affiliates. All rights reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.amazon.carbonado.qe;
import java.io.IOException;
import com.amazon.carbonado.Cursor;
import com.amazon.carbonado.FetchException;
import com.amazon.carbonado.Query;
import com.amazon.carbonado.Storable;
import com.amazon.carbonado.filter.Filter;
import com.amazon.carbonado.filter.FilterValues;
import com.amazon.carbonado.info.StorableIndex;
/**
* QueryExecutor which has a fully specified key, and so cursors produce at
* most one result.
*
* @author Brian S O'Neill
*/
public class KeyQueryExecutor<S extends Storable> extends AbstractQueryExecutor<S> {
private final Support<S> mSupport;
private final StorableIndex<S> mIndex;
private final Filter<S> mKeyFilter;
/**
* @param index index to use, which may be a primary key index
* @param score score determines how best to utilize the index
* @throws IllegalArgumentException if any parameter is null or if index is
* not unique or if score is not a key match
*/
public KeyQueryExecutor(Support<S> support, StorableIndex<S> index, FilteringScore<S> score) {
if (support == null && this instanceof Support) {
support = (Support<S>) this;
}
if (support == null || index == null || score == null) {
throw new IllegalArgumentException();
}
if (!index.isUnique() || !score.isKeyMatch()) {
throw new IllegalArgumentException();
}
mSupport = support;
mIndex = index;
mKeyFilter = score.getIdentityFilter();
}
@Override
public Class<S> getStorableType() {
// Storable type of filter may differ if index is used along with a
// join. The type of the index is the correct storable type.
return mIndex.getStorableType();
}
public Cursor<S> fetch(FilterValues<S> values) throws FetchException {
return mSupport.fetchOne(mIndex, values.getValuesFor(mKeyFilter));
}
public Cursor<S> fetch(FilterValues<S> values, Query.Controller controller)
throws FetchException
{
return mSupport.fetchOne(mIndex, values.getValuesFor(mKeyFilter), controller);
}
public Filter<S> getFilter() {
return mKeyFilter;
}
/**
* Returns an empty list.
*/
public OrderingList<S> getOrdering() {
return OrderingList.emptyList();
}
public boolean printPlan(Appendable app, int indentLevel, FilterValues<S> values)
throws IOException
{
indent(app, indentLevel);
app.append("index key match: ");
app.append(mIndex.getStorableType().getName());
newline(app);
indent(app, indentLevel);
app.append("...index: ");
mIndex.appendTo(app);
newline(app);
indent(app, indentLevel);
app.append("...key filter: ");
mKeyFilter.appendTo(app, values);
newline(app);
return true;
}
/**
* Provides support for {@link KeyQueryExecutor}.
*/
public static interface Support<S extends Storable> {
/**
* Select at most one Storable referenced by an index. The identity
* values fully specify all elements of the index, and the index is
* unique.
*
* @param index index to open, which may be a primary key index
* @param identityValues of exactly matching values to apply to index
*/
Cursor<S> fetchOne(StorableIndex<S> index, Object[] identityValues)
throws FetchException;
/**
* Select at most one Storable referenced by an index. The identity
* values fully specify all elements of the index, and the index is
* unique.
*
* @param controller optional controller which can abort query operation
* @param index index to open, which may be a primary key index
* @param identityValues of exactly matching values to apply to index
*/
Cursor<S> fetchOne(StorableIndex<S> index, Object[] identityValues,
Query.Controller controller)
throws FetchException;
}
}
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