autumnust opened a new pull request #651:
URL: https://github.com/apache/orc/pull/651
This PR:
- Add a straightforward implementation for `Dictionary` using hash table.
- Refactored RB-Tree to make code reusable, like `VisitorContextImpl`.
Moving it into `DictionaryUtils.java` to make is sharable between different
implementation of `Dictionary` interface.
- Enabling hash-based dictionary for existing tests that enables
dictionary-encoding.
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### What changes were proposed in this pull request?
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We find RB-Tree based dictionary implementation being slow in our production
workload. The performance comparison for the new hash-table based
implementation will be done as part of ORC-50.
### How was this patch tested?
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Mostly tested with added unit tests for hash-table and enabled hash-table
based dictionary in some of the existing tests.
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