package org.apache.lucene.spatial.prefix;
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.
*/
import com.spatial4j.core.shape.Point;
import com.spatial4j.core.shape.Shape;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.tokenattributes.CharTermAttribute;
import org.apache.lucene.document.Field;
import org.apache.lucene.document.FieldType;
import org.apache.lucene.index.FieldInfo;
import org.apache.lucene.queries.function.ValueSource;
import org.apache.lucene.spatial.SpatialStrategy;
import org.apache.lucene.spatial.prefix.tree.Cell;
import org.apache.lucene.spatial.prefix.tree.SpatialPrefixTree;
import org.apache.lucene.spatial.query.SpatialArgs;
import org.apache.lucene.spatial.util.ShapeFieldCacheDistanceValueSource;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;
/**
* An abstract SpatialStrategy based on {@link SpatialPrefixTree}. The two
* subclasses are {@link RecursivePrefixTreeStrategy} and {@link
* TermQueryPrefixTreeStrategy}. This strategy is most effective as a fast
* approximate spatial search filter.
*
* <h4>Characteristics:</h4>
* <ul>
* <li>Can index any shape; however only {@link RecursivePrefixTreeStrategy}
* can effectively search non-point shapes.</li>
* <li>Can index a variable number of shapes per field value. This strategy
* can do it via multiple calls to {@link #createIndexableFields(com.spatial4j.core.shape.Shape)}
* for a document or by giving it some sort of Shape aggregate (e.g. JTS
* WKT MultiPoint). The shape's boundary is approximated to a grid precision.
* </li>
* <li>Can query with any shape. The shape's boundary is approximated to a grid
* precision.</li>
* <li>Only {@link org.apache.lucene.spatial.query.SpatialOperation#Intersects}
* is supported. If only points are indexed then this is effectively equivalent
* to IsWithin.</li>
* <li>The strategy supports {@link #makeDistanceValueSource(com.spatial4j.core.shape.Point,double)}
* even for multi-valued data, so long as the indexed data is all points; the
* behavior is undefined otherwise. However, <em>it will likely be removed in
* the future</em> in lieu of using another strategy with a more scalable
* implementation. Use of this call is the only
* circumstance in which a cache is used. The cache is simple but as such
* it doesn't scale to large numbers of points nor is it real-time-search
* friendly.</li>
* </ul>
*
* <h4>Implementation:</h4>
* The {@link SpatialPrefixTree} does most of the work, for example returning
* a list of terms representing grids of various sizes for a supplied shape.
* An important
* configuration item is {@link #setDistErrPct(double)} which balances
* shape precision against scalability. See those javadocs.
*
* @lucene.internal
*/
public abstract class PrefixTreeStrategy extends SpatialStrategy {
protected final SpatialPrefixTree grid;
private final Map<String, PointPrefixTreeFieldCacheProvider> provider = new ConcurrentHashMap<>();
protected final boolean simplifyIndexedCells;
protected int defaultFieldValuesArrayLen = 2;
protected double distErrPct = SpatialArgs.DEFAULT_DISTERRPCT;// [ 0 TO 0.5 ]
public PrefixTreeStrategy(SpatialPrefixTree grid, String fieldName, boolean simplifyIndexedCells) {
super(grid.getSpatialContext(), fieldName);
this.grid = grid;
this.simplifyIndexedCells = simplifyIndexedCells;
}
/**
* A memory hint used by {@link #makeDistanceValueSource(com.spatial4j.core.shape.Point)}
* for how big the initial size of each Document's array should be. The
* default is 2. Set this to slightly more than the default expected number
* of points per document.
*/
public void setDefaultFieldValuesArrayLen(int defaultFieldValuesArrayLen) {
this.defaultFieldValuesArrayLen = defaultFieldValuesArrayLen;
}
public double getDistErrPct() {
return distErrPct;
}
/**
* The default measure of shape precision affecting shapes at index and query
* times. Points don't use this as they are always indexed at the configured
* maximum precision ({@link org.apache.lucene.spatial.prefix.tree.SpatialPrefixTree#getMaxLevels()});
* this applies to all other shapes. Specific shapes at index and query time
* can use something different than this default value. If you don't set a
* default then the default is {@link SpatialArgs#DEFAULT_DISTERRPCT} --
* 2.5%.
*
* @see org.apache.lucene.spatial.query.SpatialArgs#getDistErrPct()
*/
public void setDistErrPct(double distErrPct) {
this.distErrPct = distErrPct;
}
@Override
public Field[] createIndexableFields(Shape shape) {
double distErr = SpatialArgs.calcDistanceFromErrPct(shape, distErrPct, ctx);
return createIndexableFields(shape, distErr);
}
public Field[] createIndexableFields(Shape shape, double distErr) {
int detailLevel = grid.getLevelForDistance(distErr);
List<Cell> cells = grid.getCells(shape, detailLevel, true, simplifyIndexedCells);//intermediates cells
//TODO is CellTokenStream supposed to be re-used somehow? see Uwe's comments:
// http://code.google.com/p/lucene-spatial-playground/issues/detail?id=4
Field field = new Field(getFieldName(),
new CellTokenStream(cells.iterator()), FIELD_TYPE);
return new Field[]{field};
}
/* Indexed, tokenized, not stored. */
public static final FieldType FIELD_TYPE = new FieldType();
static {
FIELD_TYPE.setIndexed(true);
FIELD_TYPE.setTokenized(true);
FIELD_TYPE.setOmitNorms(true);
FIELD_TYPE.setIndexOptions(FieldInfo.IndexOptions.DOCS_ONLY);
FIELD_TYPE.freeze();
}
/** Outputs the tokenString of a cell, and if its a leaf, outputs it again with the leaf byte. */
final static class CellTokenStream extends TokenStream {
private final CharTermAttribute termAtt = addAttribute(CharTermAttribute.class);
private Iterator<Cell> iter = null;
public CellTokenStream(Iterator<Cell> tokens) {
this.iter = tokens;
}
CharSequence nextTokenStringNeedingLeaf = null;
@Override
public boolean incrementToken() {
clearAttributes();
if (nextTokenStringNeedingLeaf != null) {
termAtt.append(nextTokenStringNeedingLeaf);
termAtt.append((char) Cell.LEAF_BYTE);
nextTokenStringNeedingLeaf = null;
return true;
}
if (iter.hasNext()) {
Cell cell = iter.next();
CharSequence token = cell.getTokenString();
termAtt.append(token);
if (cell.isLeaf())
nextTokenStringNeedingLeaf = token;
return true;
}
return false;
}
}
@Override
public ValueSource makeDistanceValueSource(Point queryPoint, double multiplier) {
PointPrefixTreeFieldCacheProvider p = provider.get( getFieldName() );
if( p == null ) {
synchronized (this) {//double checked locking idiom is okay since provider is threadsafe
p = provider.get( getFieldName() );
if (p == null) {
p = new PointPrefixTreeFieldCacheProvider(grid, getFieldName(), defaultFieldValuesArrayLen);
provider.put(getFieldName(),p);
}
}
}
return new ShapeFieldCacheDistanceValueSource(ctx, p, queryPoint, multiplier);
}
public SpatialPrefixTree getGrid() {
return grid;
}
}