contrib/storage-jdbc/src/main/java/org/apache/drill/exec/store/jdbc/JdbcDialectFactory.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 under the License.
 */
package org.apache.drill.exec.store.jdbc;

import org.apache.calcite.sql.SqlDialect;
import org.apache.drill.exec.store.jdbc.clickhouse.ClickhouseJdbcDialect;

import java.time.Duration;

public class JdbcDialectFactory {
  public static final String JDBC_CLICKHOUSE_PREFIX = "jdbc:clickhouse";
  public static final int CACHE_SIZE = 100;
  public static final Duration CACHE_TTL = Duration.ofHours(1);
  private volatile JdbcDialect jdbcDialect;

  public JdbcDialect getJdbcDialect(JdbcStoragePlugin plugin, SqlDialect dialect) {
    // Note: any given JdbcDialectFactory instance will only ever be called with
    // a single SqlDialect so we can cache using a single member.
    JdbcDialect jd = jdbcDialect;
    if (jd == null) {
      // Double checked locking using a volatile member and a local var
      // optimisation to reduce volatile accesses.
      synchronized (this) {
        jd = jdbcDialect;
        if (jd == null) {
          jd = plugin.getConfig().getUrl().startsWith(JDBC_CLICKHOUSE_PREFIX)
                ? new ClickhouseJdbcDialect(plugin, dialect)
                : new DefaultJdbcDialect(plugin, dialect);
          jdbcDialect = jd;
        }
      }
    }
    return jd;
  }
}