rdblue commented on a change in pull request #1495:
URL: https://github.com/apache/iceberg/pull/1495#discussion_r497838143



##########
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:
       
[`StaticTableOperations`](https://github.com/apache/iceberg/blob/master/core/src/main/java/org/apache/iceberg/StaticTableOperations.java)
 might help here. We use that to inspect metadata that has already expired in 
the `ExpireSnapshotsAction`. That allows you to create a static table based on 
an older metadata location.




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