搜索和查询知识图谱服务

有两种方法可从知识图谱中检索记录。搜索允许您对知识图谱运行自由文本搜索。查询提供了一种更细致的方式，以 openCypher 查询的形式检索对知识图谱执行的记录。搜索和查询都有两种模式：非流式和流式。流式搜索和流式查询以小的 chunk 块返回结果，允许客户端立即开始处理返回的数据，而不是等待返回整个结果集后再进行处理。流式处理更快、更高效，并且将检索所有匹配的记录，即使总数超过服务定义中设置的搜索和查询限制也是如此。流的另一个好处是请求是编码的，这意味着它比传统的 HTTP GET 或 JSON POST 的 body 小得多。当试图对非常大的参数进行查询时 (例如，大型 ID 集或与复杂几何体相交)，这一点尤其重要。

搜索

使用 GraphSearchStreaming 可通过 executeSearchStreaming() 方法搜索图谱中实体和关系的属性。其他可选搜索参数（如指定要在其中进行搜索的实体或关系类型列表）可以进一步限制搜索。搜索知识图谱的最有效方法是使用流式搜索。

展开
代码块使用深色复制
        // define the search terms
        const search = new StreamingSearch({
          searchQuery: "solar",
          typeCategoryFilter: "both",
          // optional parameters
          returnSearchContext: false,
          start: 1, //start at the first record
          num: 200, //return 200 records.
          namedTypesFilter: ["Company", "Supplier", "Part"],
          globalIdsFilter: ["aiw-924", "esj-856", "snh-571", "hnk-9751", "pyo-7884", "hjl-2541"]
        });

        // search the knowledge graph
        KnowledgeGraphModule.executeSearchStreaming(
          // knowledge graph resources
          knowledgeGraph,
          // search parameters
          search
        ).then((streamingSearchResult) => {
          // the result of a streaming search is a readableStream which must be read to access the data.
          readStream(streamingSearchResult);
        });
展开

查询

使用 executeQueryStreaming() 方法可检索实体和关系的具体子集及其属性。查询图谱使用 openCypher 查询的 GeoScene 实现，该查询支持只读操作。在从图谱返回的结果和返回的数据结构方面，查询提供了更大的灵活性。例如，假设有一个供应链图谱，该图谱包含制造 Plant 的实体，其制造的 Part 由 Supplier 进行购买；工厂和它生产的零件之间有一种 produces 关系，供应商和它购买零件的工厂之间有一种 buys_part 关系。

要查找 Supplier 类型的前十个实体，可以使用查询 MATCH (m:Supplier) RETURN m LIMIT 10。要发现哪些零件 (p) 是由哪些工厂 (pl) 生产的，可以使用查询通过 produces 关系来匹配实体，例如 MATCH (pl:Plant)-[ :produces]->(p) RETURN pl,p。GraphQueryStreaming 还提供了将参数绑定到查询 (如边界框) 的功能。有关其他查询参数，请参阅 GraphQueryStreaming。

展开
代码块使用深色复制
        // select all Supplier's that are in the Washington DC area and the parts that they buy
        const query = `MATCH (s:Supplier)-[:buys_part]-(p:Part)
               geoscene.graph.ST_Intersects($geom, s.geometry)
               RETURN s,p`;

        KnowledgeGraphModule.executeQueryStreaming(knowledgeGraph, {
          openCypherQuery: query,
          bindParameters: {
            //bounding box around Washington DC
            geom: new Polygon({
              rings: [
                [
                  [38, -78],
                  [39, -78],
                  [39, -76],
                  [-38, -76],
                  [-38, -78]
                ]
              ]
            })
          }
        }).then((streamingQueryResult) => {
          // the result of a streaming query is a readableStream which must be read to access the data.
          readStream(streamingQueryResult);
        });
展开

使用流结果

流式搜索或流式查询的结果是 GraphQueryStreamingResult，其中包含一个可读流，必须使用 getReader() 函数读取该流才能访问数据。可读流将返回记录块，直到返回所有记录。每个块都可立即处理，例如将数据添加到表或将具有几何的实体添加到地图。

展开
代码块使用深色复制
        // a function to read the stream returned from the search
        const readStream = async (streamingQueryResult) => {
          let time = Date.now();
          let reader = streamingQueryResult.resultRowsStream.getReader();
          try {
            while (true) {
              const { done, value } = await reader.read();
              if (done) {
                console.log(`Stream completed and closed: ${(Date.now() - time) / 1000} seconds`, value);
                break;
              }
              // begin working with the data from the returned chunk immediately.
              // list the parts bought by each supplier
              let supplierParts = [];

              // each element of the result array will contain one supplier and one part it buys
              for (let v in value){
                let supplier = value[v][0].properties.Name
                let part = value [v][1].properties.Name
                if(!(supplier in supplierParts)){
                  supplierParts[supplier] = [];
                }

                // collect parts by supplier that buys them
                supplierParts[supplier].push(part);
              }
              // make a table that lists the suppliers and the parts they buy
              let table = document.getElementById('supplierTableBody');
              for (let supplier in supplierParts){
                table.appendChild(`<tr><td>${supplier}</td><td>${supplierParts.supplier.join(', ')}</td>`);
              }
              //  Entities that have geometry can be drawn on the map
              addToMap(value);
              // Since
            }
            // if there is an error in returning the stream or the stream is aborted
          } catch (err) {
            if (err.name === "AbortError") {
              console.log("Request aborted as expected");
            } else {
              throw err;
            }
          }
        };

        // function to add entities with geometry to a map
        function addToMap(records) {
          let features = [];
          //extract the geometry from the returned results and add it to a feature layer
          for (let i = 0; i < records.length; i++) {
            let item = records[i][0];
            let props = item.properties;
            // if the returned item contains geometry,
            //extract the geometry information to create features
            if ("shape" in props) {
              features.push({
                geometry: {
                  type: props.shape.type,
                  x: props.shape.longitude,
                  y: props.shape.latitude
                },
                attributes: props
              });
            }
          }

          // create feature layer
          let featureLayer = new FeatureLayer({
            source: features,
            renderer: {
              type: "unique-value", // autocasts as new UniqueValueRenderer()
              defaultSymbol: {
                type: "simple-marker", // autocasts as new SimpleMarkerSymbol()
                size: 2,
                color: "#009816",
                outline: null
              }
            }
          });
          map.add(featureLayer);
        }
展开

GeoScene Maps SDK for JavaScript

搜索和查询知识图谱服务

搜索

查询

使用流结果