tustvold opened a new pull request, #2765:
URL: https://github.com/apache/arrow-rs/pull/2765
# Which issue does this PR close?
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Closes #.
# Rationale for this change
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The use of HashMap without a hasher nor keys, is a little perverse. It turns
out hashbrown has a RawTable API that we can use directly instead. As an added
bonus this provides a very minor performance improvement
```
string_dictionary_builder/(dict_size:20, len:1000, key_len: 5)
time: [18.563 µs 18.605 µs 18.647 µs]
change: [-4.5058% -3.6392% -2.7326%] (p = 0.00 <
0.05)
Performance has improved.
Found 8 outliers among 100 measurements (8.00%)
3 (3.00%) low mild
2 (2.00%) high mild
3 (3.00%) high severe
string_dictionary_builder/(dict_size:100, len:1000, key_len: 5)
time: [21.649 µs 21.693 µs 21.738 µs]
change: [-2.2389% -1.8649% -1.5032%] (p = 0.00 <
0.05)
Performance has improved.
Found 1 outliers among 100 measurements (1.00%)
1 (1.00%) high severe
string_dictionary_builder/(dict_size:100, len:1000, key_len: 10)
time: [21.696 µs 21.715 µs 21.734 µs]
change: [-2.0519% -1.8956% -1.6960%] (p = 0.00 <
0.05)
Performance has improved.
Found 1 outliers among 100 measurements (1.00%)
1 (1.00%) high severe
string_dictionary_builder/(dict_size:100, len:10000, key_len: 10)
time: [176.06 µs 176.14 µs 176.22 µs]
change: [-0.9251% -0.6795% -0.4273%] (p = 0.00 <
0.05)
Change within noise threshold.
Found 5 outliers among 100 measurements (5.00%)
1 (1.00%) low mild
2 (2.00%) high mild
2 (2.00%) high severe
string_dictionary_builder/(dict_size:100, len:10000, key_len: 100)
time: [463.94 µs 464.12 µs 464.30 µs]
change: [-0.1715% -0.0733% +0.0237%] (p = 0.15 >
0.05)
No change in performance detected.
Found 2 outliers among 100 measurements (2.00%)
1 (1.00%) high mild
1 (1.00%) high severe
```
# What changes are included in this PR?
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sometimes worth providing a summary of the individual changes in this PR.
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Switches to using hashbrown::RawTable in place of HashMap and the raw entry
API
# Are there any user-facing changes?
No
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