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

Parse the createdBy version string once during FileMetaData construction
and cache the result as a transient field. This avoids redundant
VersionParser.parse() calls at every downstream call site (R×C times
during footer decode alone).

Author: asifsmohammed

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 +44,7 @@ public enum EncryptionType {
   private final MessageType schema;
   private final Map<String, String> keyValueMetaData;
   private final String createdBy;
+  private final transient ParsedVersion writerVersion;
   private final InternalFileDecryptor fileDecryptor;
   private final EncryptionType encryptionType;
 
@@ -80,6 +83,7 @@ public FileMetaData(
     this.keyValueMetaData =
         unmodifiableMap(Objects.requireNonNull(keyValueMetaData, "keyValueMetaData cannot be null"));
     this.createdBy = createdBy;
+    this.writerVersion = parseVersion(createdBy);
     this.fileDecryptor = fileDecryptor;
     this.encryptionType = encryptionType;
   }
@@ -118,4 +122,23 @@ public InternalFileDecryptor getFileDecryptor() {
   public EncryptionType getEncryptionType() {
     return encryptionType;
   }
+
+  /**
+   * @return the parsed writer version, or {@code null} if {@code createdBy} is null, empty, or unparseable
+   */
+  @JsonIgnore
+  public ParsedVersion getWriterVersion() {
+    return writerVersion;
+  }
+
+  private static ParsedVersion parseVersion(String createdBy) {
+    if (createdBy == null || createdBy.isEmpty()) {
+      return null;
+    }
+    try {
+      return VersionParser.parse(createdBy);
+    } catch (RuntimeException | VersionParser.VersionParseException e) {
+      return null;
+    }
+  }
 }

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

@@ -0,0 +1,76 @@
+/*
+ * 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();
+  }
+}