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Posted to commits@druid.apache.org by "kgyrtkirk (via GitHub)" <gi...@apache.org> on 2024/08/07 12:44:23 UTC
[I] String columns from Frames are always decoded during access (druid)
kgyrtkirk opened a new issue, #16856:
URL: https://github.com/apache/druid/issues/16856
Looking into some perf results it turned out that during queries involving windows the significance of restoring a `String` object from the `Frame` representation has some performance impact:
* string data is stored as `utf8` bytes
* operations like `compare` and such use a `ObjectColumnAccessorBase` to access the value
* since the type is `String` it have to be decoded
* `StringUtils#fromUtf8` allocates a new bytearray; copies stuff
* `java.lang.String` constructor is used to decode the bytes from `UTF_8`
<details>
<summary>some benchmark results/tries</summary>
tried forcing the encoding to `ISO-8859-1` which could have some advantages; but that will still retain a lot from the above
```
// base
Benchmark (rowsPerSegment) (schema) (storageType) Mode Cnt Score Error Units
SqlWindowFunctionsBenchmark.windowWithSorter 100000 auto mmap avgt 5 812.024 ± 24.003 ms/op
SqlWindowFunctionsBenchmark.windowWithoutSorter 100000 auto mmap avgt 5 611.424 ± 47.396 ms/op
// ISO-8859-1
Benchmark (rowsPerSegment) (schema) (storageType) Mode Cnt Score Error Units
SqlWindowFunctionsBenchmark.windowWithSorter 100000 auto mmap avgt 5 779.933 ± 29.665 ms/op
SqlWindowFunctionsBenchmark.windowWithoutSorter 100000 auto mmap avgt 5 613.465 ± 37.255 ms/op
```
</details>
note: For the Partitioner its not even relevant if the String is lesser or smaller - it just needs to know if its the same or not; the same could not be said about the Sorter.
note: might be interesting to try and materialize the frame into object arrays before processing; so that the conversion only happens once
<details>
<summary>some flamegraphs about it</summary>
### the sorter and the partitioner are affected by this
### zoomed in a bit
<details>
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Re: [I] String columns from Frames are always decoded during access (druid)
Posted by "naanagon (via GitHub)" <gi...@apache.org>.
naanagon commented on issue #16856:
URL: https://github.com/apache/druid/issues/16856#issuecomment-2401575019
@kgyrtkirk
I would like to work on this
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Re: [I] String columns from Frames are always decoded during access (druid)
Posted by "github-actions[bot] (via GitHub)" <gi...@apache.org>.
github-actions[bot] closed issue #16856: String columns from Frames are always decoded during access
URL: https://github.com/apache/druid/issues/16856
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Re: [I] String columns from Frames are always decoded during access (druid)
Posted by "github-actions[bot] (via GitHub)" <gi...@apache.org>.
github-actions[bot] commented on issue #16856:
URL: https://github.com/apache/druid/issues/16856#issuecomment-3190274327
This issue has been closed due to lack of activity. If you think that
is incorrect, or the issue requires additional review, you can revive the issue at
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Re: [I] String columns from Frames are always decoded during access (druid)
Posted by "github-actions[bot] (via GitHub)" <gi...@apache.org>.
github-actions[bot] commented on issue #16856:
URL: https://github.com/apache/druid/issues/16856#issuecomment-3081933843
This issue has been marked as stale due to 280 days of inactivity.
It will be closed in 4 weeks if no further activity occurs. If this issue is still
relevant, please simply write any comment. Even if closed, you can still revive the
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Thank you for your contributions.
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