[GitHub] [incubator-hudi] bvaradar commented on a change in pull request #1457: [HUDI-741] Added checks to validate Hoodie's schema evolution.

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bvaradar commented on a change in pull request #1457: [HUDI-741] Added checks to validate Hoodie's schema evolution.
URL: https://github.com/apache/incubator-hudi/pull/1457#discussion_r405979601
 
 

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 File path: hudi-common/src/main/java/org/apache/hudi/common/table/TableSchemaResolver.java
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+/*
+ * 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.hudi.common.table;
+
+import java.io.IOException;
+
+import org.apache.avro.Schema;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.Path;
+import org.apache.hudi.common.avro.SchemaCompatibility;
+import org.apache.hudi.common.model.HoodieCommitMetadata;
+import org.apache.hudi.common.model.HoodieFileFormat;
+import org.apache.hudi.common.model.HoodieLogFile;
+import org.apache.hudi.common.table.log.HoodieLogFormat;
+import org.apache.hudi.common.table.log.HoodieLogFormat.Reader;
+import org.apache.hudi.common.table.log.block.HoodieAvroDataBlock;
+import org.apache.hudi.common.table.log.block.HoodieLogBlock;
+import org.apache.hudi.common.table.timeline.HoodieActiveTimeline;
+import org.apache.hudi.common.table.timeline.HoodieInstant;
+import org.apache.hudi.common.util.Option;
+import org.apache.hudi.common.util.collection.Pair;
+import org.apache.hudi.exception.HoodieException;
+import org.apache.hudi.exception.InvalidTableException;
+import org.apache.log4j.LogManager;
+import org.apache.log4j.Logger;
+import org.apache.parquet.avro.AvroSchemaConverter;
+import org.apache.parquet.format.converter.ParquetMetadataConverter;
+import org.apache.parquet.hadoop.ParquetFileReader;
+import org.apache.parquet.hadoop.metadata.ParquetMetadata;
+import org.apache.parquet.schema.MessageType;
+
+/**
+ * Helper class to read schema from data files and log files and to convert it between different formats.
+ */
+public class TableSchemaResolver {
+
+  private static final Logger LOG = LogManager.getLogger(TableSchemaResolver.class);
+  private HoodieTableMetaClient metaClient;
+
+  public TableSchemaResolver(HoodieTableMetaClient metaClient) {
+    this.metaClient = metaClient;
+  }
+
+  /**
+   * Gets the schema for a hoodie table. Depending on the type of table, read from any file written in the latest
+   * commit. We will assume that the schema has not changed within a single atomic write.
+   *
+   * @return Parquet schema for this table
+   * @throws Exception
+   */
+  public MessageType getDataSchema() throws Exception {
 
 Review comment:
   Since we log schema now in commit metadata, can't we just try to read it first. If it is not there, then we can try reading from parquet file.

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