korowa opened a new pull request, #5057:
URL: https://github.com/apache/arrow-datafusion/pull/5057
# Which issue does this PR close?
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Closes #137.
# Rationale for this change
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Improved performance for reading single parquet file / parquet files in
quantity less than number of cores / parquet files having significant variation
in size in multicore runtime
# What changes are included in this PR?
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1) `parallel_file_scan` execution setting - by default false, when true -
file scan operations parallelized for Parquet files
2) `FormatScanMetadata` - container for format-specific metadata required
for planning/optimizing scans. It seemed to be reasonable to calculate file
ranges along with statistics, and avoid additional metadata fetch. Returned by
`FileFormat` method `fetch_format_scan_metadata` (replacement for `infer_stats`)
3) `FormatScanMetadataCache` - replacement for `StatisticsCache` - appeared
for the same reason `FormatScanMetadata` was introduced. Listing options are
not available from outside, and there are no methods for their modification, so
simply caching metadata object retrieved from `fetch_format_scan_metadata`
method seems to be safe.
4) `split_files` - now performed over tuples of (`PartitionedFile`,
`FileRanges`) and handle them as a basic unit for Scan
# Are these changes tested?
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Tests for `fetch_format_scan_metadata` and `split_files` added.
# Are there any user-facing changes?
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New configuration setting `parallel_file_scan`
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