pvary commented on a change in pull request #1495: URL: https://github.com/apache/iceberg/pull/1495#discussion_r494114559
########## File path: mr/src/main/java/org/apache/iceberg/mr/hive/HiveIcebergMetaHook.java ########## @@ -0,0 +1,161 @@ +/* + * 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.mr.hive; + +import java.util.HashSet; +import java.util.Properties; +import java.util.Set; +import java.util.stream.Collectors; +import java.util.stream.Stream; +import org.apache.hadoop.conf.Configuration; +import org.apache.hadoop.hive.metastore.HiveMetaHook; +import org.apache.hadoop.hive.metastore.api.MetaException; +import org.apache.iceberg.BaseMetastoreTableOperations; +import org.apache.iceberg.PartitionSpecParser; +import org.apache.iceberg.Schema; +import org.apache.iceberg.SchemaParser; +import org.apache.iceberg.Table; +import org.apache.iceberg.exceptions.NoSuchTableException; +import org.apache.iceberg.hive.HiveTableOperations; +import org.apache.iceberg.mr.Catalogs; +import org.apache.iceberg.mr.InputFormatConfig; +import org.apache.iceberg.relocated.com.google.common.base.Preconditions; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +public class HiveIcebergMetaHook implements HiveMetaHook { + private static final Logger LOG = LoggerFactory.getLogger(HiveIcebergMetaHook.class); + private static final Set<String> PARAMETERS_TO_REMOVE = Stream + .of(InputFormatConfig.TABLE_SCHEMA, InputFormatConfig.PARTITION_SPEC, Catalogs.LOCATION, Catalogs.NAME) + .collect(Collectors.toCollection(HashSet::new)); + private static final Set<String> PROPERTIES_TO_REMOVE = Stream + .of(InputFormatConfig.HIVE_DELETE_BACKING_TABLE, "storage_handler", "EXTERNAL") + .collect(Collectors.toCollection(HashSet::new)); + + private final Configuration conf; + private Table icebergTable = null; + private Properties catalogProperties; + private boolean deleteIcebergTable; + + public HiveIcebergMetaHook(Configuration conf) { + this.conf = conf; + } + + @Override + public void preCreateTable(org.apache.hadoop.hive.metastore.api.Table hmsTable) { + catalogProperties = getCatalogProperties(hmsTable); + try { + icebergTable = Catalogs.loadTable(conf, catalogProperties); + + Preconditions.checkArgument(catalogProperties.getProperty(InputFormatConfig.TABLE_SCHEMA) == null, + "Iceberg table already created - can not use provided schema"); + Preconditions.checkArgument(catalogProperties.getProperty(InputFormatConfig.PARTITION_SPEC) == null, + "Iceberg table already created - can not use provided partition specification"); + + LOG.info("Iceberg table already exists {}", icebergTable); + } catch (NoSuchTableException nte) { + String schemaString = catalogProperties.getProperty(InputFormatConfig.TABLE_SCHEMA); + Preconditions.checkNotNull(schemaString, "Please provide a table schema"); + // Just check if it is parsable, and later use for partition specification parsing + Schema schema = SchemaParser.fromJson(schemaString); + + String specString = catalogProperties.getProperty(InputFormatConfig.PARTITION_SPEC); + if (specString != null) { + // Just check if it is parsable + PartitionSpecParser.fromJson(schema, schemaString); + } + + // Allow purging table data if the table is created now and not set otherwise + if (hmsTable.getParameters().get(InputFormatConfig.HIVE_DELETE_BACKING_TABLE) == null) { + hmsTable.getParameters().put(InputFormatConfig.HIVE_DELETE_BACKING_TABLE, "TRUE"); Review comment: I can see 2 different use-cases for Hive tables Iceberg tables: 1. Table is created and used only from Hive. When we drop the table we want to drop the underlying Iceberg table as well 2. Table is created outside of Hive but want to read it from Hive as well. We create the Hive table above the Iceberg table but when we drop the Hive table we do not want to drop the underlying Iceberg table. The proposed solution is: - Default behavior: When the table is created from Hive and it needs to create the underlying Iceberg table then Hive will master the data. If the underlying Iceberg table is already there then Hive will not master the data. When the Hive table is dropped then the underlying Iceberg table is only dropped if Hive is mastering the data. - HIVE_DELETE_BACKING_TABLE could override the default behavior when dropping the table There is 1 exception: If the HiveCatalog is used it is obviously not possible to keep the table if we drop the HMS table. 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