GraphQueryStreaming

另请参阅

• knowledgeGraphService

// sample streaming query using bind parameters
// to search for entities with a the `name` property that matches a specific string
// or have their geometry within a bounding box.
// get all parts bought by each supplier.
// query returns both the supplier and the part it buys.
const query = `MATCH (s:Supplier)-[:buys_part]-(p:Part)
               WHERE s.name=$name OR geoscene.graph.ST_Intersects($geom, s.geometry)
               RETURN s,p`;

KnowledgeGraphModule.executeQueryStreaming(
  knowledgeGraph,
  {
    openCypherQuery: query,
    bindParameters: {
      name: "Supplier 1",
      geom: new Polygon({
        rings: [
          [
            [38,-78],
            [39, -78],
            [39, -76],
            [-38, -76],
            [-38, -78],
          ],
       ],
    }),
  }
}).then((streamingQueryResult)=>{
  // streaming query returns a readableStream which must be read to access the returned graph data
  readStream(streamingQueryResult);
})

// a function to read the readable stream returned from the above query
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(`All records returned, stream closed: ${(Date.now() - time) / 1000} seconds`);
        break;
      }
      console.log(`Streaming chunk returned in: ${(Date.now() - time) / 1000} seconds`, value);
      // use the results
      // 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 (var 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);
        console.log(supplierParts);
        // result printed to the console: {Supplier 1:[Part1], Supplier 3:[Part2, Part3]}
      }
    }
  } catch (err) {
    if (err.name === "AbortError") {
      console.log("Request aborted as expected");
    } else {
      throw err;
    }
  }
};

// result stream from above query after it has been read
"Streaming chunk returned in: 0.082 seconds"
[
  [{
    "declaredClass": "geoscene.rest.knowledgeGraph.Entity",
    "properties": {
      "Name": "Supplier 1",
      "City": "Washington DC",
      "EmployeeCount": 31
    },
    "typeName": "Supplier",
    "id": "{57FDF2F3-34C8-48EF-9A3B-76ED9314C4D2}"
  },{
    "declaredClass": "geoscene.rest.knowledgeGraph.Entity",
    "properties": {
      "Part_ID": 695401,
      "Name": "Part1",
      "Minimum_quantity": 360
    },
    "typeName": "Part",
    "id": "{IWN51W4-1AW8-A2W6-1AW5F-1AW8F9F4W51AS}",
  }],
  [{
    "declaredClass": "geoscene.rest.knowledgeGraph.Entity",
    "properties": {
      "Name": "Supplier 2",
      "City": "Baltimore",
      "EmployeeCount": 53
    },
    "typeName": "Supplier",
    "id": "{1A4W8F5W-1WA8-5W6A-A1W8-A1W5F8W3S482A}"
  },{
    "declaredClass": "geoscene.rest.knowledgeGraph.Entity",
    "properties": {
      "Part_ID": 695401,
      "Name": "Part2",
      "Minimum_quantity": 2500
    },
    "typeName": "Part",
    "id": "{A1W5F8W4F-A1W8-1894-16A5-A86WF4A8SFWD}",
  }],
  [{
    "declaredClass": "geoscene.rest.knowledgeGraph.Entity",
    "properties": {
      "Name": "Supplier 2",
      "City": "Baltimore",
      "EmployeeCount": 53
    },
    "typeName": "Supplier",
    "id": "{1A4W8F5W-1WA8-5W6A-A1W8-L5H4G8RT1PK3}"
  },{
    "declaredClass": "geoscene.rest.knowledgeGraph.Entity",
    "properties": {
      "Part_ID": 695401,
      "Name": "Part3",
      "Minimum_quantity": 5000
    },
    "typeName": "Part",
    "id": "{PTJ51FT-KY4H-1GY5-G1Y8-G1Y5K49G8Y4GHJ}",
  }]
]

// aborting the query
// create instance of native browser abort controller
const controller = new AbortController();
// create query
KnowledgeGraphModule
  .executeQueryStreaming(
    knowledgeGraph,
    {
      openCypherQuery: "MATCH (n) RETURN n LIMIT 100",
    },
    {
      signal: controller.signal,
    }
  )
  .then((streamingQueryResult) => {
    readStream(streamingQueryResult);
  })
  // indicate that the stream was aborted
  .catch((err) => {
    if (err.name === "AbortError") {
      console.log("Request aborted as expected");
    }

// abort the query after half a second
setTimeout(() => {
  console.log("Sending abort signal");
  controller.abort();
}, 500);

构造函数

new GraphQueryStreaming(properties)

参数

properties Object optional 有关可能传递给构造函数的属性的完整列表，请参见属性。