xuefuz commented on a change in pull request #8007: [FLINK-11474][table] Add ReadableCatalog, ReadableWritableCatalog, and other … URL: https://github.com/apache/flink/pull/8007#discussion_r275734781
########## File path: flink-table/flink-table-common/src/main/java/org/apache/flink/table/catalog/ReadableCatalog.java ########## @@ -0,0 +1,116 @@ +/* + * 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.flink.table.catalog; + +import org.apache.flink.table.catalog.exceptions.DatabaseNotExistException; +import org.apache.flink.table.catalog.exceptions.TableNotExistException; + +import java.util.List; + +/** + * This interface is responsible for reading database/table/views/UDFs from a registered catalog. + * It connects a registered catalog and Flink's Table API. + */ +public interface ReadableCatalog { + + /** + * Open the catalog. Used for any required preparation in initialization phase. + */ + void open(); + + /** + * Close the catalog when it is no longer needed and release any resource that it might be holding. + */ + void close(); + + // ------ databases ------ + + /** + * Get the name of the current database of this type of catalog. This is used when users refers an object in the catalog + * without specifying a database. For example, the current db in a Hive Metastore is 'default' by default. + * + * @return the name of the current database + */ + String getCurrentDatabase(); + + /** + * Set the database with the given name as the current database. A current database is used when users refers an object + * in the catalog without specifying a database. + * + * @param databaseName the name of the database + */ + void setCurrentDatabase(String databaseName) throws DatabaseNotExistException; + + /** + * Get the names of all databases in this catalog. + * + * @return The list of the names of all databases + */ + List<String> listDatabases(); + + /** + * Get a database from this catalog. + * + * @param databaseName Name of the database + * @return The requested database + * @throws DatabaseNotExistException if the database does not exist + */ + CatalogDatabase getDatabase(String databaseName) throws DatabaseNotExistException; + + /** + * Check if a database exists in this catalog. + * + * @param databaseName Name of the database + */ + boolean databaseExists(String databaseName); Review comment: I noticed databaseExists() or schemaExists() are fairly commonly used in other database systems. On the other hand, word "contains" sounds more like a container, which isn't exactly what a catalog is about. Let me know if you're strong on this. Thanks. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org With regards, Apache Git Services
