examples/flink-sql/src/main/java/FlinkExample.java

/*
 * 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
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import static org.apache.flink.table.api.Expressions.$;
import static org.apache.flink.table.api.Expressions.call;

import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
import org.apache.flink.table.api.EnvironmentSettings;
import org.apache.flink.table.api.Table;
import org.apache.flink.table.api.bridge.java.StreamTableEnvironment;
import org.apache.sedona.flink.SedonaFlinkRegistrator;
import org.apache.sedona.flink.expressions.Constructors;

public class FlinkExample {
  static String[] pointColNames = {"geom_point", "name_point", "event_time", "proc_time"};

  static String[] polygonColNames = {"geom_polygon", "name_polygon", "event_time", "proc_time"};

  public static void main(String[] args) {
    testS2SpatialJoin(10);
  }

  public static void testS2SpatialJoin(int testDataSize) {
    StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
    EnvironmentSettings settings = EnvironmentSettings.newInstance().inStreamingMode().build();
    StreamTableEnvironment tableEnv = StreamTableEnvironment.create(env, settings);
    SedonaFlinkRegistrator.registerType(env);
    SedonaFlinkRegistrator.registerFunc(tableEnv);

    // Create a fake WKT string table source
    Table pointWktTable =
        Utils.createTextTable(env, tableEnv, Utils.createPointWKT(testDataSize), pointColNames);

    // Create a geometry column
    Table pointTable =
        pointWktTable.select(
            call("ST_GeomFromWKT", $(pointColNames[0])).as(pointColNames[0]), $(pointColNames[1]));

    // Create S2CellID
    pointTable =
        pointTable.select(
            $(pointColNames[0]),
            $(pointColNames[1]),
            call("ST_S2CellIDs", $(pointColNames[0]), 6).as("s2id_array"));
    // Explode s2id array
    tableEnv.createTemporaryView("pointTable", pointTable);
    pointTable =
        tableEnv.sqlQuery(
            "SELECT geom_point, name_point, s2id_point FROM pointTable CROSS JOIN UNNEST(pointTable.s2id_array) AS tmpTbl1(s2id_point)");

    // Create a fake WKT string table source
    Table polygonWktTable =
        Utils.createTextTable(env, tableEnv, Utils.createPolygonWKT(testDataSize), polygonColNames);
    // Create a geometry column
    Table polygonTable =
        polygonWktTable.select(
            call(Constructors.ST_GeomFromWKT.class.getSimpleName(), $(polygonColNames[0]))
                .as(polygonColNames[0]),
            $(polygonColNames[1]));
    // Create S2CellID
    polygonTable =
        polygonTable.select(
            $(polygonColNames[0]),
            $(polygonColNames[1]),
            call("ST_S2CellIDs", $(polygonColNames[0]), 6).as("s2id_array"));
    // Explode s2id array
    tableEnv.createTemporaryView("polygonTable", polygonTable);
    polygonTable =
        tableEnv.sqlQuery(
            "SELECT geom_polygon, name_polygon, s2id_polygon FROM polygonTable CROSS JOIN UNNEST(polygonTable.s2id_array) AS tmpTbl2(s2id_polygon)");

    // TODO: TableImpl.print() occurs EOF Exception due to
    // https://issues.apache.org/jira/browse/FLINK-35406
    // Use polygonTable.execute().print() when FLINK-35406 is fixed.
    polygonTable.execute().collect().forEachRemaining(row -> System.out.println(row));

    // Join two tables by their S2 ids
    Table joinResult =
        pointTable.join(polygonTable).where($("s2id_point").isEqual($("s2id_polygon")));
    // Optional: remove false positives
    joinResult = joinResult.where(call("ST_Contains", $("geom_polygon"), $("geom_point")));
    joinResult.execute().collect().forEachRemaining(row -> System.out.println(row));
  }
}