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Neo4J空间数据存储知识解答

shasha 2021年06月14日 数据库 147 0

1.Neo4j Spatial 简介

1.1Neo4j Spatial概念

Neo4j Spatial项目是图数据库Neo4j的一个插件,它通过将空间数据映射到图模型(graph model),它将对象和关系当作顶点和边存储在图模型中。因而使得Neo4j具有空间数据的导入,存储,查询等功能[8]。Neo4j Spatial支持的地理要素遵循OpenGIS的规范[9],包括点(point),线段(line-string),面(polygon),多点(multipoint),多线段(multi-linestring)等简单要素。Neo4j Spatial使用R树作为空间索引,主要是集成了Lucene 的索引库,支持的空间查询包括覆盖(cover),被覆盖(cover by),包含(contian),相交(intersect)等。一般而言,R树会将叶子结点(COUNT,LEVEL,<OIi,MBRi>)上几何要素分组并用它们的数据矩形来表示,相比PostGIS所使用的优化过GisT[13]索引要低效,会使Neo4j在范围查询上效率有所不及PostGIS,但它对适合图模型的数据(如网络数据)操作效率非常高[14]。综上所述,Neo4j在符合图数据模型的分析中如邻近搜索,路径分析等这些特定类型的应用有非常大的优势。

Neo4J图数据库实践系列

图数据库实践系列 (一)--Neo4J简介与安装 IT虾米网

图数据库实践系列 (二)--Neo4J空间数据存储 IT虾米网

图数据库实践系列 (三)--Neo4j Spatial的REST集成 IT虾米网

1.2 Neo4j Spatial特性

Neo4j Spatial的部分核心特性包括

  • 支持Esri Shapefile格式,OSM(OpenStreetMap)格式(只支持.osm格式)(补充:Open Street Map目前逐步适用PBF替代OSM)
  • 支持所有通用的几何要素
  • 在空间查询的时候支持拓扑操作
  • 允许任何图数据都实现空间操作功能
  • 能够将单一图层或者数据集拆分成多个子图层

2.Neo4j Spatial安装

2.1 EGit安装

EGit是Eclipse团队提供的Git插件,它基于JGit(Git的java实现版本)实现的,允许在Eclipse中实现Git的各种命令[15]。它的安装和其他插件一样,在eclipse中选择Help->Install New Software,加入Update site IT虾米网 会如图1所示:

图1 安装EGit

安装成功的话,需要重启Eclipse。File ->New -> Other,会看到Git的字样。

2.2 M2eclipse安装

M2eclipse是Maven的Eclipse插件,项目的目标是提供为Eclipse 提供一流的Maven支持,使它能够更方便地编辑POM文件,构建项目等[16]。同样可以通过Update Site 安装:IT虾米网。如图2所示:

图2 安装M2Eclipse

安装成功的话,需要重启Eclipse。File ->New -> Other,会看到Maven的字样。

2.2Neo4j Spatial安装

Neo4j Spatial源码可以在Github下载,我们通过以上安装的两个插件,来构建和安装我们的Neo4j Spatial项目。首先在eclipse中File中导入Git项目,

File -> Import -> Git -> Project from Git.如果本地已经存在Git库,可以选择Local.我们远程下载Spatial,选择URI,如图3所示。

图3 选择远程库

输入Neo4j Spatial URI,然后Next,如图-4所示:

图4 输入URI

EGit会自动Fetch回所有的源码,我们可以按照自己需要选择特定版本,然后Next。如图5所示:

图5 选择源码版本

然后可以一直Next,直至选择导入的项目类型,选择Import as general projcet.如图6 所示:

图6 导入项目

再Next然后点finish 完成neo4j spatial 的导出。此时,还需要将该项目转化成Maven Project ,选中项目,右键:Configure ->Convert to Maven Project.最后我们得到了一个git管理下的maven项目。使用如下命令来安装Neo4j Spatial。

 
mvn clean install
 

在eclipse操作是 Run as ->5. Maven Build ->输入构建目标。 如图7所示:

图7 构建Neo4j Spatial 项目

M2eclipse会自动构建工程。如果安装失败的话,可以使用如下命令跳过单元测试

 
mvn clean install -DskipTests
 

最后eclipse的console会报出build success。

3.Neo4j Spatial 空间数据读取

 3.1地理图层与编码

Spatial 库中首先需要定义图层中几何要素,可供查询的索引,同时图层是否可编辑 ,其次是确定几何编码接口。Spatial类库提供的默认图层是标准图层,使用WKBGeometryEncoder,将所有的要素以字节数组的形式来存 储。地理数据中实体的属性会当作图数据模型中顶点的属性来存储。OSMLayer 是支持Open Street Map格式的特殊图层,neo4j使用单个完全图[17]来存储该图层。同时 OMSLayer继承动态图层,允许包含任意个子图层。

 3.2导入shapefile

导入shapefile大概过程是1.生存Neo4j数据库(调用已有) 2.实例化,并调用ShapefileImporter 3.关闭数据库  实例代码如下所示:

复制代码
package edu.sirc.gis.data; 

import java.io.FileNotFoundException; import java.io.IOException; import java.nio.charset.Charset;

import org.geotools.data.shapefile.shp.ShapefileException; import org.neo4j.gis.spatial.Layer; import org.neo4j.gis.spatial.ShapefileImporter; import org.neo4j.gis.spatial.SpatialDatabaseService; import org.neo4j.graphdb.GraphDatabaseService; import org.neo4j.kernel.EmbeddedGraphDatabase;

public class importShapefiletest {

/** 
 * @param args 
 * import shapefile to neo4j database 
 * just Extract from the org.neo4j.gis.spatial.testfordoc 
 */ 
private String databasepath="/home/vent/environment/neo4j/gis"; 

public void importShapfile() throws ShapefileException, FileNotFoundException, IOException
{
System.out.println("\n=== Test Import Shapefile ===");

 </span><span class="typ">GraphDatabaseService</span><span class="pln"> graphdb </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">new</span><span class="pln"> </span><span class="typ">EmbeddedGraphDatabase</span><span class="pun">(</span><span class="pln">databasepath</span><span class="pun">);</span><span class="pln"> 
 </span><span class="kwd">try</span><span class="pln"> 
 </span><span class="pun">{</span><span class="pln"> 
     </span><span class="typ">ShapefileImporter</span><span class="pln"> shpImporter </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">new</span><span class="pln"> </span><span class="typ">ShapefileImporter</span><span class="pun">(</span><span class="pln">graphdb</span><span class="pun">);</span><span class="pln"> 
     shpImporter</span><span class="pun">.</span><span class="pln">importFile</span><span class="pun">(</span><span class="str">"/home/vent/environment/neo4j/data/shp/river.shp"</span><span class="pun">,</span><span class="pln"> </span><span class="str">"river"</span><span class="pun">,</span><span class="pln"> </span><span class="typ">Charset</span><span class="pun">.</span><span class="pln">forName</span><span class="pun">(</span><span class="str">"UTF-8"</span><span class="pun">));</span><span class="pln"> 
 </span><span class="pun">}</span><span class="pln"> 
 </span><span class="kwd">finally</span><span class="pln"> 
 </span><span class="pun">{</span><span class="pln"> 
     graphdb</span><span class="pun">.</span><span class="pln">shutdown</span><span class="pun">();</span><span class="pln"> 
 </span><span class="pun">}</span><span class="pln"> 

}
public static void main(String[] args) throws ShapefileException, FileNotFoundException, IOException {
// TODO Auto-generated method stub
importShapefiletest isf
= new importShapefiletest();
isf
.importShapfile();
}

}

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3.3导入OSM

导入OSM的过程和导入shapefile差异不大,旧版Neo4j Spatial 提供了批量读入的接口BatchInserter,可以加快大文件的导入。具体JavaDoc请参阅打包后的文档。

复制代码
package edu.sirc.gis.data; 

import java.io.File; import java.nio.charset.Charset; import java.util.HashMap; import java.util.Map;

import org.neo4j.gis.spatial.osm.OSMImporter; import org.neo4j.graphdb.GraphDatabaseService; import org.neo4j.kernel.EmbeddedGraphDatabase; import org.neo4j.kernel.impl.batchinsert.BatchInserter; import org.neo4j.kernel.impl.batchinsert.BatchInserterImpl;

public class importOSMTest {

/** 
 * @param args 
 */ 
//import osm file into the default db for server . 
private String databasepath="/home/vent/environment/neo4j/data/graph.db"; 
private String osmPath="/home/vent/Downloads/"; 
private static final Map&lt;String, String&gt; NORMAL_CONFIG = new HashMap&lt;String, String&gt;(); 
static { 
    NORMAL_CONFIG.put( "neostore.nodestore.db.mapped_memory", "50M" ); 
    NORMAL_CONFIG.put( "neostore.relationshipstore.db.mapped_memory", "120M" ); 
    NORMAL_CONFIG.put( "neostore.propertystore.db.mapped_memory", "150M" ); 
    NORMAL_CONFIG.put( "neostore.propertystore.db.strings.mapped_memory", "200M" ); 
    NORMAL_CONFIG.put( "neostore.propertystore.db.arrays.mapped_memory", "0M" ); 
    NORMAL_CONFIG.put( "dump_configuration", "false" ); 
} 
private void  importOSM() throws Exception 
{ 
</span><span class="typ">OSMImporter</span><span class="pln"> osmIm </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">new</span><span class="pln"> </span><span class="typ">OSMImporter</span><span class="pun">(</span><span class="str">"FUJIAN"</span><span class="pun">);</span><span class="pln"> 
</span><span class="typ">Map</span><span class="pun">&amp;</span><span class="pln">lt</span><span class="pun">;</span><span class="typ">String</span><span class="pun">,</span><span class="pln"> </span><span class="typ">String</span><span class="pun">&amp;</span><span class="pln">gt</span><span class="pun">;</span><span class="pln"> config </span><span class="pun">=</span><span class="pln"> NORMAL_CONFIG</span><span class="pun">;</span><span class="pln"> 
</span><span class="lit">@SuppressWarnings</span><span class="pun">(</span><span class="str">"deprecation"</span><span class="pun">)</span><span class="pln"> 
</span><span class="com">//BatchInserter baIns = new BatchInserterImpl(osmPath,config);</span><span class="pln"> 
</span><span class="typ">String</span><span class="pln"> dataset </span><span class="pun">=</span><span class="str">"/home/vent/Downloads/Fujian.osm"</span><span class="pun">;</span><span class="pln"> 
</span><span class="com">//osmIm.importFile(baIns,dataset,false);</span><span class="pln"> 
 
</span><span class="typ">GraphDatabaseService</span><span class="pln"> db </span><span class="pun">=</span><span class="pln"> </span><span class="kwd">new</span><span class="pln"> </span><span class="typ">EmbeddedGraphDatabase</span><span class="pun">(</span><span class="pln">databasepath</span><span class="pun">);</span><span class="pln"> 
osmIm</span><span class="pun">.</span><span class="pln">importFile</span><span class="pun">(</span><span class="pln">db</span><span class="pun">,</span><span class="pln"> dataset</span><span class="pun">);</span><span class="pln"> 
osmIm</span><span class="pun">.</span><span class="pln">reIndex</span><span class="pun">(</span><span class="pln">db</span><span class="pun">,</span><span class="pln"> </span><span class="lit">100</span><span class="pun">);</span><span class="pln"> 
db</span><span class="pun">.</span><span class="pln">shutdown</span><span class="pun">();</span><span class="pln"> 

}
public static void main(String[] args) throws Exception {
// TODO Auto-generated method stub
importOSMTest iOSM
= new importOSMTest();
iOSM
.importOSM();
}

}

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下讲会讲述Neo4j Spatial与GeoServer 的集成,以及与Neo4j Server的集成。

[8]Neo4j Spatial  IT虾米网

[9] OpenGIS® Simple Features Specification For SQL

[10]Vicknair, C. et al. 2010. A Comparison of a Graph Database and a Relational Database. In Proceedings of the 48th annual Southeast regional conference

[11]Apache Lucene IT虾米网

[12]R-tree IT虾米网

[13]GiST  IT虾米网

[14]空间数据库索引技术 郭薇 郭菁 上海交通大学出版社  P104-105 2006

[15]EGit IT虾米网

[16]Maven Integration (m2e) IT虾米网

原文地址:http://neo4j.com.cn/topic/581925ac5ab6525b6d6ab80b

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