[ARROW-8658] [C++][Dataset] Implement subtree pruning for FileSystemDataset::GetFragments

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.17.0
• Fix Version/s: 4.0.0
• Component/s: C++
• Labels: dataset pull-request-available
• External issue URL: https://github.com/apache/arrow/issues/24819
• Assignee: Ben Kietzman
• Reporter: Ben Kietzman
• Created: 30/Apr/20 19:02
• Updated: 11/Jan/23 08:01
• Resolved: 12/Mar/21 15:57

Description

This is a very handy optimization for large datasets with multiple partition fields. For example, given a hive-style directory $base_dir/a=3/ and a filter "a"_ == 2 none of its files or subdirectories need be examined.

After ARROW-8318 FileSystemDataset stores only files so subtree pruning (whose implementation depended on the presence of directories to represent subtrees) was disabled. It should be possible to reintroduce this without reference to directories by examining partition expressions directly and extracting a tree structure from their subexpressions.

Issue Links

• is related to: ARROW-11781 [Python] Reading small amount of files from a partitioned dataset is unexpectedly slow
• links to: GitHub Pull Request #9670