henrib commented on code in PR #6441: URL: https://github.com/apache/hive/pull/6441#discussion_r3652530105
########## standalone-metastore/metastore-rest-catalog/src/main/java/org/apache/iceberg/hive/MetadataLocator.java: ########## @@ -0,0 +1,104 @@ +/* + * 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.iceberg.hive; + +import org.apache.hadoop.hive.metastore.IMetaStoreClient; +import org.apache.hadoop.hive.metastore.api.GetProjectionsSpec; +import org.apache.hadoop.hive.metastore.api.NoSuchObjectException; +import org.apache.hadoop.hive.metastore.api.Table; +import org.apache.hadoop.hive.metastore.client.builder.GetTableProjectionsSpecBuilder; +import org.apache.iceberg.BaseMetastoreTableOperations; +import org.apache.iceberg.ClientPool; +import org.apache.iceberg.MetadataTableType; +import org.apache.iceberg.catalog.TableIdentifier; +import org.apache.iceberg.exceptions.NoSuchTableException; +import org.apache.thrift.TException; + +import java.util.Collections; +import java.util.List; + +/** + * Fetches the location of a given metadata table. + * <p>Since the location mutates with each transaction, this allows determining if a cached version of the + * table is the latest known in the HMS database.</p> + */ +public class MetadataLocator { + private static final org.slf4j.Logger LOGGER = org.slf4j.LoggerFactory.getLogger(MetadataLocator.class); + private static final GetProjectionsSpec PARAM_SPEC = new GetTableProjectionsSpecBuilder() + .includeParameters() // only fetches table.parameters + .build(); + private final HiveCatalog catalog; + + public MetadataLocator(HiveCatalog catalog) { + this.catalog = catalog; + } + + public HiveCatalog getCatalog() { + return catalog; + } + + /** + * Returns the location of the metadata table identified by the given identifier, or null if the table is + * not a metadata table. + * <p>This uses the Thrift API to fetch the table parameters, which is more efficient than fetching the entire table object.</p> + * @param identifier the identifier of the metadata table to fetch the location for + * @return the location of the metadata table, or null if the table does not exist or is not a metadata table + * @throws NoSuchTableException if the table does not exist + */ + public String getLocation(TableIdentifier identifier) { + final ClientPool<IMetaStoreClient, TException> clients = catalog.clientPool(); + final String catName = catalog.name(); + final TableIdentifier baseTableIdentifier; + if (!catalog.isValidIdentifier(identifier)) { + if (!isValidMetadataIdentifier(identifier)) { + return null; + } else { + baseTableIdentifier = TableIdentifier.of(identifier.namespace().levels()); + } + } else { + baseTableIdentifier = identifier; + } + String database = baseTableIdentifier.namespace().level(0); + String tableName = baseTableIdentifier.name(); + try { + List<Table> tables = clients.run( + client -> client.getTables(catName, database, Collections.singletonList(tableName), PARAM_SPEC) Review Comment: The whole idea is to make this the 'smallest/fastest/leanest' possible check and to avoid materializing a whole Table object. -- 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. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
