[SPARK-55273][SQL] Replace ParquetFileReader.open().getFooter() with readFooter() to avoid unnecessary operations in ParquetFooterReader

[LuciferYang]

What changes were proposed in this pull request?

This pr replace ParquetFileReader.open().getFooter() with ParquetFileReader.readFooter() to avoid unnecessary operations in ParquetFooterReader

Why are the changes needed?

Compared to ParquetFileReader.readFooter(), ParquetFileReader.open() performs more operations as follows:

    this.converter = new ParquetMetadataConverter(options);
    this.file = file;
    this.f = f;
    this.options = options;
    this.footer = footer;

    this.fileMetaData = footer.getFileMetaData();
    this.fileDecryptor = fileMetaData.getFileDecryptor(); // must be called before filterRowGroups!
    if (null != fileDecryptor && fileDecryptor.plaintextFile()) {
      this.fileDecryptor = null; // Plaintext file. No need in decryptor
    }

    try {
      this.blocks = filterRowGroups(footer.getBlocks());
    } catch (Exception e) {
      // In case that filterRowGroups throws an exception in the constructor, the new stream
      // should be closed. Otherwise, there's no way to close this outside.
      f.close();
      throw e;
    }
    this.blockIndexStores = listWithNulls(this.blocks.size());
    this.blockRowRanges = listWithNulls(this.blocks.size());
    for (ColumnDescriptor col : footer.getFileMetaData().getSchema().getColumns()) {
      paths.put(ColumnPath.get(col.getPath()), col);
    }

    if (options.usePageChecksumVerification()) {
      this.crc = new CRC32();
      this.crcAllocator = ReusingByteBufferAllocator.strict(options.getAllocator());
    } else {
      this.crc = null;
      this.crcAllocator = null;
    }

https://github.com/apache/parquet-java/blob/fac0c746532e133beb928a7f6a7e57b510b477a1/parquet-hadoop/src/main/java/org/apache/parquet/hadoop/ParquetFileReader.java#L960-L1016

And these operations can be omitted for the requirement of readFooter.

Does this PR introduce any user-facing change?

No

How was this patch tested?

Pass GitHub Acitons

Was this patch authored or co-authored using generative AI tooling?

No

[github-actions]

JIRA Issue Information

=== Improvement SPARK-55273 ===
Summary: Replace ParquetFileReader.open().getFooter() with readFooter() to avoid unnecessary operations in ParquetFooterReader
Assignee: None
Status: Open
Affected: ["4.2.0"]

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This comment was automatically generated by GitHub Actions

[LuciferYang]

https://github.com/LuciferYang/spark/actions/runs/21471431559/job/61844708507

[dongjoon-hyun]

+1, LGTM. Thank you, @LuciferYang .

[LuciferYang]

Merged into master. Thanks @dongjoon-hyun and @pan3793