okumin commented on code in PR #5882: URL: https://github.com/apache/hive/pull/5882#discussion_r2182641070
########## standalone-metastore/metastore-rest-catalog/src/main/java/org/apache/iceberg/rest/HMSEventListener.java: ########## @@ -0,0 +1,96 @@ +/* + * 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.rest; + +import org.apache.hadoop.conf.Configuration; +import org.apache.hadoop.hive.metastore.MetaStoreEventListener; +import org.apache.hadoop.hive.metastore.api.MetaException; +import org.apache.hadoop.hive.metastore.api.Table; +import org.apache.hadoop.hive.metastore.events.AlterTableEvent; +import org.apache.hadoop.hive.metastore.events.DropDatabaseEvent; +import org.apache.hadoop.hive.metastore.events.DropTableEvent; +import org.apache.hadoop.hive.metastore.events.ReloadEvent; +import org.apache.iceberg.catalog.Catalog; +import org.slf4j.Logger; + +/** + * IcebergEventListener is a Hive Metastore event listener that invalidates the cache + * of the HMSCachingCatalog when certain events occur, such as altering or dropping a table. + */ +public class HMSEventListener extends MetaStoreEventListener { Review Comment: Let me try to explain my intention. As you know, the location of the metadata top is stored in `metadata_location`. The most important point is `file:/opt/hive/data/warehouse/test/metadata/00000-165e08e2-9cea-47b1-9eef-45921f238fe2.metadata.json` is immutable. Whenever we update the table, the path will change. ``` | CREATE EXTERNAL TABLE `test`( | | `id` int) | | ROW FORMAT SERDE | | 'org.apache.iceberg.mr.hive.HiveIcebergSerDe' | | STORED BY | | 'org.apache.iceberg.mr.hive.HiveIcebergStorageHandler' | | | | LOCATION | | 'file:/opt/hive/data/warehouse/test' | | TBLPROPERTIES ( | | 'TRANSLATED_TO_EXTERNAL'='TRUE', | | 'bucketing_version'='2', | | 'current-schema'='{"type":"struct","schema-id":0,"fields":[{"id":1,"name":"id","required":false,"type":"int"}]}', | | 'external.table.purge'='TRUE', | | 'format-version'='2', | | 'iceberg.orc.files.only'='false', | | 'metadata_location'='file:/opt/hive/data/warehouse/test/metadata/00000-165e08e2-9cea-47b1-9eef-45921f238fe2.metadata.json', | ``` Therefore, the following code does not include the staleness problem. ```java Map<String, org.apache.iceberg.Table> cache = new HashMap(); // We should use Guava's cache or something cache.put("file:/opt/hive/data/warehouse/test/metadata/00000-165e08e2-9cea-47b1-9eef-45921f238fe2.metadata.json", icebergTable); ``` On `loadTable`, we will use the cache in the following way. ```java org.apache.hadoop.hive.metastore.api.Table hmsTable = rdbms.getTable(tableName); String metadataLocation = hmsTable.getParameters().get("metadata_location"); // this might be wrong org.apache.iceberg.Table cachedTable = cache.get(metaedataLocation); if (cachedTable != null) { return cachedTable; } // We will access S3, and then build the org.apache.iceberg.Table ``` This is suboptimal because we access the RDBMS every time. However, we can eliminate S3 latency without staleness issues. I haven't run the PoC, so I'm not sure if it really works. -- 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: gitbox-unsubscr...@hive.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: gitbox-unsubscr...@hive.apache.org For additional commands, e-mail: gitbox-h...@hive.apache.org
