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https://issues.apache.org/jira/browse/LUCENE-8126?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16320912#comment-16320912
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ASF GitHub Bot commented on LUCENE-8126:
----------------------------------------
Github user dsmiley commented on a diff in the pull request:
https://github.com/apache/lucene-solr/pull/302#discussion_r160768053
--- Diff:
lucene/spatial-extras/src/java/org/apache/lucene/spatial/prefix/tree/S2PrefixTreeCell.java
---
@@ -0,0 +1,285 @@
+/*
+ * 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.
+ */
+
+package org.apache.lucene.spatial.prefix.tree;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+import com.google.common.geometry.S2CellId;
+import org.apache.lucene.util.BytesRef;
+import org.locationtech.spatial4j.shape.Shape;
+import org.locationtech.spatial4j.shape.SpatialRelation;
+
+/**
+ * This class represents a S2 pixel in the RPT.
+ *
+ * @lucene.internal
+ */
+class S2PrefixTreeCell implements Cell {
+
+ //Faces of S2 Geometry
+ private static S2CellId[] FACES = new S2CellId[6];
+ static {
+ FACES[0] = S2CellId.fromFacePosLevel(0, 0, 0);
+ FACES[1] = S2CellId.fromFacePosLevel(1, 0, 0);
+ FACES[2] = S2CellId.fromFacePosLevel(2, 0, 0);
+ FACES[3] = S2CellId.fromFacePosLevel(3, 0, 0);
+ FACES[4] = S2CellId.fromFacePosLevel(4, 0, 0);
+ FACES[5] = S2CellId.fromFacePosLevel(5, 0, 0);
+ }
+
+ /*Special character to define a cell leaf*/
+ private static final byte LEAF = '+';
+
+ /*Tokens are used to serialize cells*/
+ private static final byte[] TOKENS;
+ /*Map containing mapping between tokens and integer values*/
+ private static final Map<Byte,Integer> PIXELS;
--- End diff --
Since this map has a small set of fixed values that have numeric
equivalents, perhaps we can do direct addressing into an array?
> Spatial prefix tree based on S2 geometry
> ----------------------------------------
>
> Key: LUCENE-8126
> URL: https://issues.apache.org/jira/browse/LUCENE-8126
> Project: Lucene - Core
> Issue Type: New Feature
> Components: modules/spatial-extras
> Reporter: Ignacio Vera
>
> Hi [~dsmiley],
> I have been working on a prefix tree based on goggle S2 geometry
> (https://s2geometry.io/) to be used mainly with Geo3d shapes with very
> promising results, in particular for complex shapes (e.g polygons). Using
> this pixelization scheme reduces the size of the index, improves the
> performance of the queries and reduces the loading time for non-point shapes.
> If you are ok with this contribution and before providing any code I would
> like to understand what is the correct/prefered approach:
> 1) Add new depency to the S2 library
> (https://mvnrepository.com/artifact/io.sgr/s2-geometry-library-java). It has
> Apache 2.0 license so it should be ok.
> 2) Create a utility class with all methods necessary to navigate the S2 tree
> and create shapes from S2 cells (basically port what we need from the library
> into Lucene).
> What do you think?
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