Github user liancheng commented on the pull request:
https://github.com/apache/spark/pull/7154#issuecomment-122651410
Thanks for contributing this patch! I have two high level comments here:
1. PR #7396 also tries to accelerate Parquet metadata discovery/refreshing
by several means, and has been proven to be quite effective. We've observed
~50x speedup on large partitioned S3 dataset with schema merging enabled.
1. How about adding a check for `FileStatus.getModificationTime`? Namely,
we only read footers of new files and existing files that are modified since
last refresh. This can be particularly useful for appending.
In general, this PR can be a good complement for #7396.
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