Parquet Incremental Sync

[sapienza88]

Important Read

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• Fixed JSON parsing error when persisting state
• Added unit tests for schema evolution

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[rahil-c]

I can do first review for this @the-other-tim-brown @vinishjail97

[vinishjail97]

Why are we writing new parquet files again like this through the writer? I think there's some misunderstanding with the parquet incremental sync feature here.

Parquet Incremental Sync Requirements.

1. You have a target table where parquet files [p1/f1.parquet, p1/f2.parquet, p2/f1.parquet] have been synced to hudi, iceberg and delta for example.
2. In the source changes some changes have been made a new file in partition p1 was added and p2's file was deleted. The incremental sync should now sync the new changes incrementally.

@sapienza88 It's better to align on the approach first here before we push PR's. Can you add the approach for parquet incremental sync in the PR description or any google doc if possible?

[sapienza88]

@vinishjail97 we simply want to append the file to where it belongs in the table (under the right partition). so we need to find the partition path (from the table's) where the file should be injected (doing this through path construction). In order to write the file the only way as far as I know is the ParquetWriter. After doing so, the Source can filter the files based on the modfication dates.

[sapienza88]

@vinishjail97 I added some comments on the functions so that the approach is clearer. All above suggestions were also taken into account in my last commit.