xuefuz commented on a change in pull request #8404: [FLINK-11476][table] Create
CatalogManager to manage multiple catalogs
URL: https://github.com/apache/flink/pull/8404#discussion_r286155068
##########
File path:
flink-table/flink-table-api-java/src/main/java/org/apache/flink/table/api/TableEnvironment.java
##########
@@ -280,6 +315,142 @@
*/
void sqlUpdate(String stmt, QueryConfig config);
+ /**
+ * Gets the current default catalog name of the current session.
+ *
+ * @return The current default catalog name that is used for the path
resolution.
+ * @see TableEnvironment#useCatalog(String)
+ */
+ String getCurrentCatalog();
+
+ /**
+ * Sets the current catalog to the given value. It also sets the default
+ * database to the catalog's default one. To assign both catalog and
database explicitly
+ * see {@link TableEnvironment#useDatabase(String, String)}.
+ *
+ * <p>This is used during the resolution of object paths. Both the
catalog and database are optional
+ * when referencing catalog objects(tables, views etc.). The algorithm
looks for requested objects in following
+ * paths in that order:
+ * <ol>
+ * <li>{@code
[current-catalog].[current-database].[requested-path]}</li>
+ * <li>{@code [current-catalog].[requested-path]}</li>
+ * <li>{@code [requested-path]}</li>
+ * </ol>
+ *
+ * <p>Example:
+ *
+ * <p>Given structure with default catalog set to {@code
default-catalog} and default database set to
+ * {@code default-database}.
+ * <pre>
+ * root:
+ * |- default-catalog
+ * |- default-database
+ * |- tab1
+ * |- db1
+ * |- tab1
+ * |- cat1
+ * |- db1
+ * |- tab1
+ * </pre>
+ *
+ * <p></p>The following table describes resolved paths:
+ * <table>
+ * <thead>
+ * <tr>
+ * <th>Requested path</th>
+ * <th>Resolved path</th>
+ * </tr>
+ * </thead>
+ * <tbody>
+ * <tr>
+ * <td>tab1</td>
+ * <td>default-catalog.default-database.tab1</td>
+ * </tr>
+ * <tr>
+ * <td>db1.tab1</td>
+ * <td>default-catalog.db1.tab1</td>
+ * </tr>
+ * <tr>
+ * <td>cat1.db1.tab1</td>
+ * <td>cat1.db1.tab1</td>
+ * </tr>
+ * </tbody>
+ * </table>
+ *
+ * @param catalogName The name of the catalog to set as the current
default catalog.
+ * @throws CatalogException thrown if a catalog with given name could
not be set as the default one
+ */
+ void useCatalog(String catalogName);
+
+ /**
+ * Gets the current default database name of the running session.
+ *
+ * @return The name of the current database of the current catalog.
+ * @see TableEnvironment#useDatabase(String, String)
+ */
+ String getCurrentDatabase();
+
+ /**
+ * Sets the current default catalog and database. That path will be
used as the default one
+ * when looking for unqualified object names.
+ *
+ * <p>This is used during the resolution of object paths. Both the
catalog and database are optional
+ * when referencing catalog objects(tables, views etc.). The algorithm
looks for requested objects in following
+ * paths in that order:
+ * <ol>
+ * <li>{@code
[current-catalog].[current-database].[requested-path]}</li>
+ * <li>{@code [current-catalog].[requested-path]}</li>
+ * <li>{@code [requested-path]}</li>
+ * </ol>
+ *
+ * <p>Example:
+ *
+ * <p>Given structure with default catalog set to {@code
default-catalog} and default database set to
+ * {@code default-database}.
+ * <pre>
+ * root:
+ * |- default-catalog
+ * |- default-database
+ * |- tab1
+ * |- db1
+ * |- tab1
+ * |- cat1
+ * |- db1
+ * |- tab1
+ * </pre>
+ *
+ * <p></p>The following table describes resolved paths:
+ * <table>
+ * <thead>
+ * <tr>
+ * <th>Requested path</th>
+ * <th>Resolved path</th>
+ * </tr>
+ * </thead>
+ * <tbody>
+ * <tr>
+ * <td>tab1</td>
+ * <td>default-catalog.default-database.tab1</td>
+ * </tr>
+ * <tr>
+ * <td>db1.tab1</td>
+ * <td>default-catalog.db1.tab1</td>
+ * </tr>
+ * <tr>
+ * <td>cat1.db1.tab1</td>
+ * <td>cat1.db1.tab1</td>
+ * </tr>
+ * </tbody>
+ * </table>
+ *
+ * @param catalogName The name of the catalog to set as the current
catalog.
+ * @param databaseName The name of the database to set as the current
database.
+ * @throws CatalogException thrown if the given catalog and database
could not be set as the default ones
+ */
+ void useDatabase(
+ String catalogName,
Review comment:
This form is useful, as our DDL will have "use catalogName.databaseName" as
well as "use databaseName". Additionally, it might make sense also provide
useDatabase(databaseName), without which, user has to figure out the catalog
name in order to switch databases in the current catalog.
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