Add periodic Parquet file merging by time period

[Copilot]

Periodic Parquet File Merging Implementation

Implemented feature to periodically merge small Parquet files into larger consolidated files by configured time periods (hourly, daily, weekly, monthly).

Changes Made:

• Add configuration options for merge settings

  • merge_enabled: Enable/disable file merging
  • merge_period: Time-based merge interval (hour, day, week, month)
  • merge_min_files: Minimum number of files to trigger a merge
  • merge_on_flush: Merge files during flush operations

• Create merge functionality

  • Add merge_files() method to DataSink interface
  • Implement merge in LocalSink
  • Implement merge in S3Sink
  • Implement merge in HDFSSink
  • Handle dictionary encoding compatibility issues
  • Group files by time period
  • Delete original files after successful merge

• Integrate into pipeline

  • Pass merge configuration from SinkConfig to sinks
  • Support merge on flush option
  • Environment variable support

• Add comprehensive tests (11 new tests)

  • Test merge disabled by default
  • Test merge by hour/day
  • Test minimum file threshold
  • Test merge on flush
  • Test merge with partitioning
  • Test S3 merge
  • Test config loading

• Update documentation

  • Add merge configuration section to README
  • Document merge periods and triggers
  • Add example configuration file
  • Document environment variables

• Code quality

  • All tests passing (45 tests, 0 failures)
  • Black formatting applied
  • Linter clean (ruff)
  • Code coverage: 56% overall, 81% for LocalSink
  • Address code review feedback
  • Python 3.9+ compatible

Key Features:

✅ Flexible Time Periods: Merge by hour, day, week, or month
✅ Minimum File Threshold: Only merge when enough files exist
✅ Partitioning Support: Works with partitioned data
✅ Multi-Storage: Works with S3, HDFS, and local filesystems
✅ Schema Compatibility: Handles dictionary encoding in Parquet files
✅ Automatic Cleanup: Deletes original files after merge
✅ Python 3.9+ Compatible: Uses os.walk() for broad compatibility

Benefits:

• Reduces small file problem in analytics systems
• Improves query performance in ClickHouse, Presto, Spark
• Reduces metadata overhead
• Better resource utilization in distributed systems

Original prompt

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This section details on the original issue you should resolve

<issue_title>Periodically merge the data in the folder</issue_title>
<issue_description>Parquet files should be merged by a configured period (like by hour or by day etc.)</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Periodically merge the data in the folder #8

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[slhmy]

Fix format and lint issues @copilot

Run black --check src/ tests/
would reformat /home/runner/work/fs-data-sink/fs-data-sink/src/fs_data_sink/sinks/hdfs_sink.py
would reformat /home/runner/work/fs-data-sink/fs-data-sink/src/fs_data_sink/sinks/local_sink.py
would reformat /home/runner/work/fs-data-sink/fs-data-sink/src/fs_data_sink/sinks/s3_sink.py

Oh no! 💥 💔 💥
3 files would be reformatted, 22 files would be left unchanged.

[Copilot]

Fix format and lint issues @copilot

...

Fixed in baef957. Ran black formatter on all three sink files to resolve the formatting issues.