GH-3696: Cache ParsedVersion in FileMetaData to eliminate redundant parsing

parquet-hadoop/src/main/java/org/apache/parquet/hadoop/metadata/FileMetaData.java

@@ -24,6 +24,8 @@
 import java.io.Serializable;
 import java.util.Map;
 import java.util.Objects;
+import org.apache.parquet.VersionParser;
+import org.apache.parquet.VersionParser.ParsedVersion;
 import org.apache.parquet.crypto.InternalFileDecryptor;
 import org.apache.parquet.schema.MessageType;
 
@@ -42,6 +44,8 @@ public enum EncryptionType {
   private final MessageType schema;
   private final Map<String, String> keyValueMetaData;
   private final String createdBy;
+  private transient volatile ParsedVersion writerVersion;
+  private transient volatile boolean writerVersionParsed;
   private final InternalFileDecryptor fileDecryptor;
   private final EncryptionType encryptionType;
 
@@ -118,4 +122,25 @@ public InternalFileDecryptor getFileDecryptor() {
   public EncryptionType getEncryptionType() {
     return encryptionType;
   }
+
+  /**
+   * Returns the parsed writer version from the {@code createdBy} string, or {@code null}
+   * if {@code createdBy} is null, empty, or unparseable. The result is computed lazily
+   * and cached. Callers that need to distinguish missing vs. unparseable can check
+   * {@link #getCreatedBy()}.
+   */
+  @JsonIgnore
+  public ParsedVersion getWriterVersion() {
+    if (!writerVersionParsed) {
+      if (createdBy != null && !createdBy.isEmpty()) {
+        try {
+          writerVersion = VersionParser.parse(createdBy);
+        } catch (RuntimeException | VersionParser.VersionParseException e) {
+          // leave writerVersion as null — parse failed
+        }
+      }
+      writerVersionParsed = true;
+    }
+    return writerVersion;
+  }
 }

parquet-hadoop/src/test/java/org/apache/parquet/hadoop/metadata/FileMetaDataTest.java

@@ -0,0 +1,77 @@
+/*
+ * 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.parquet.hadoop.metadata;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.util.Collections;
+import org.apache.parquet.schema.MessageType;
+import org.apache.parquet.schema.PrimitiveType;
+import org.apache.parquet.schema.Type;
+import org.junit.jupiter.api.Test;
+
+class FileMetaDataTest {
+
+  private static final MessageType SCHEMA = new MessageType(
+      "test", new PrimitiveType(Type.Repetition.REQUIRED, PrimitiveType.PrimitiveTypeName.INT32, "id"));
+
+  @Test
+  void validCreatedByIsParsed() {
+    FileMetaData meta =
+        new FileMetaData(SCHEMA, Collections.emptyMap(), "parquet-mr version 1.12.0 (build abc123)");
+
+    assertThat(meta.getWriterVersion()).isNotNull();
+    assertThat(meta.getWriterVersion().application).isEqualTo("parquet-mr");
+    assertThat(meta.getWriterVersion().version).isEqualTo("1.12.0");
+    assertThat(meta.getWriterVersion().appBuildHash).isEqualTo("abc123");
+  }
+
+  @Test
+  void nullCreatedByReturnsNullWriterVersion() {
+    FileMetaData meta = new FileMetaData(SCHEMA, Collections.emptyMap(), null);
+
+    assertThat(meta.getWriterVersion()).isNull();
+    assertThat(meta.getCreatedBy()).isNull();
+  }
+
+  @Test
+  void emptyCreatedByReturnsNullWriterVersion() {
+    FileMetaData meta = new FileMetaData(SCHEMA, Collections.emptyMap(), "");
+
+    assertThat(meta.getWriterVersion()).isNull();
+  }
+
+  @Test
+  void unparseableCreatedByReturnsNullWriterVersion() {
+    FileMetaData meta = new FileMetaData(SCHEMA, Collections.emptyMap(), "no-version-here");
+
+    assertThat(meta.getWriterVersion()).isNull();
+  }
+
+  @Test
+  void versionWithoutBuildHash() {
+    FileMetaData meta = new FileMetaData(SCHEMA, Collections.emptyMap(), "parquet-mr version 1.8.0");
+
+    assertThat(meta.getWriterVersion()).isNotNull();
+    assertThat(meta.getWriterVersion().application).isEqualTo("parquet-mr");
+    assertThat(meta.getWriterVersion().version).isEqualTo("1.8.0");
+    assertThat(meta.getWriterVersion().appBuildHash).isNull();
+  }
+
+}