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Druid adapter for Calcite

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/*
 * 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.calcite.adapter.druid;

import org.apache.calcite.schema.Schema;
import org.apache.calcite.schema.SchemaFactory;
import org.apache.calcite.schema.SchemaPlus;

import java.util.List;
import java.util.Map;

/**
 * Schema factory that creates Druid schemas.
 *
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 * Druid schema operandsOperand Description Required
url URL of Druid's query node.
 *     The default is "http://localhost:8082". No
coordinatorUrl URL of Druid's coordinator node.
 *     The default is url, replacing "8082" with "8081",
 *     for example "http://localhost:8081". No
 */
public class DruidSchemaFactory implements SchemaFactory {
  /** Default Druid URL. */
  public static final String DEFAULT_URL = "http://localhost:8082";

  public Schema create(SchemaPlus parentSchema, String name,
      Map operand) {
    final String url = operand.get("url") instanceof String
        ? (String) operand.get("url")
        : DEFAULT_URL;
    final String coordinatorUrl = operand.get("coordinatorUrl") instanceof String
        ? (String) operand.get("coordinatorUrl")
        : url.replace(":8082", ":8081");
    // "tables" is a hidden attribute, copied in from the enclosing custom
    // schema
    final boolean containsTables = operand.get("tables") instanceof List
        && ((List) operand.get("tables")).size() > 0;
    return new DruidSchema(url, coordinatorUrl, !containsTables);
  }
}

// End DruidSchemaFactory.java

Operand	Description	Required
url	URL of Druid's query node. * The default is "http://localhost:8082".	No
coordinatorUrl	URL of Druid's coordinator node. * The default is `url`, replacing "8082" with "8081", * for example "http://localhost:8081".	No