sdks/java/extensions/sql/src/main/java/org/apache/beam/sdk/extensions/sql/meta/provider/TableProvider.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.beam.sdk.extensions.sql.meta.provider;

import java.util.Collections;
import java.util.Map;
import java.util.Set;
import javax.annotation.Nullable;
import org.apache.beam.sdk.extensions.sql.BeamSqlTable;
import org.apache.beam.sdk.extensions.sql.impl.BeamCalciteSchema;
import org.apache.beam.sdk.extensions.sql.impl.JdbcDriver;
import org.apache.beam.sdk.extensions.sql.meta.Table;

/**
 * A {@code TableProvider} handles the metadata CRUD of a specified kind of tables.
 *
 * <p>So there will be a provider to handle textfile(CSV) based tables, there is a provider to
 * handle MySQL based tables, a provider to handle Casandra based tables etc.
 *
 * <p><i>Note:</i> all implementations marked with {@code @AutoService(TableProvider.class)} are
 * automatically loaded by CLI or other cases when {@link JdbcDriver} is used with default
 * connection parameters.
 */
public interface TableProvider {
  /** Gets the table type this provider handles. */
  String getTableType();

  /** Creates a table. */
  void createTable(Table table);

  /**
   * Drops a table.
   *
   * @param tableName
   */
  void dropTable(String tableName);

  /** Get all tables from this provider. */
  Map<String, Table> getTables();

  /** Get a specific table from this provider it is present, or null if it is not present. */
  default @Nullable Table getTable(String tableName) {
    return getTables().get(tableName);
  }

  /** Build a {@link BeamSqlTable} using the given table meta info. */
  BeamSqlTable buildBeamSqlTable(Table table);

  /**
   * Returns all sub-providers, e.g. sub-schemas. Temporary, this logic needs to live in {@link
   * BeamCalciteSchema}.
   */
  default Set<String> getSubProviders() {
    return Collections.emptySet();
  }

  /**
   * Returns a sub-provider, e.g. sub-schema. Temporary, this logic needs to live in {@link
   * BeamCalciteSchema}.
   */
  default TableProvider getSubProvider(String name) {
    return null;
  }
}