gabotechs opened a new pull request, #24826:
URL: https://github.com/apache/datafusion/pull/24826
## Which issue does this PR close?
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- Closes #.
## Rationale for this change
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The `ComposedPhysicalExtensionCodec` allowed to register multiple codecs,
which are tried one by one until one works. When one works, the index of the
list that occupies the codec that works is stored in the encoded payload for
later decoding:
```text
## Encoding
[
MyFirstCodec, <- tried, but did not work
MySecondCodec, <- tried, but did not work
MyThirdCodec, <- tried, and it work, store index 2 in payload
MyFourthCodec
]
payload { index: 2, data: ... }
## Decoding
payload { index: 2, data: ... }
[
MyFirstCodec,
MySecondCodec,
MyThirdCodec, <- index is 2, just this codec is attempted
MyFourthCodec
]
```
The issue with this setup is that codecs can only be added to the end of the
list, otherwise, while decoding, the index will be messed up and decoding will
fail. In a setup with progressive rollouts this is very likely to happen.
While working in a small team, it's reasonable to expect developers to
behave and just add new codecs at the end, however, when there are many teams
contributing to the same list, with a non-centralized piece of code that has
mutable access to it, it's easy to be in the situation where new codecs are not
added at the end.
## 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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Introduces a new `ComposedNamedPhysicalExtensionCodec` that identifies
encoded payloads by codec name instead of by index in a list. This way,
registration order does not matter, and this problem becomes irrepresentable:
```text
## Encoding
{
"MyFirstCodec": MyFirstCodec, <- tried, but did not work
"MySecondCodec": MySecondCodec, <- tried, but did not work
"MyThirdCodec": MyThirdCodec, <- it worked!
"MyFourthCodec": MyFourthCodec
}
payload { name: "MyThirdCodec", data: ... }
## Decoding
payload { index: "MyThirdCodec", data: ... }
{
"MyFourthCodec": MyFourthCodec,
"MyThirdCodec": MyThirdCodec, <- use this one, no matter the order
"MyFirstCodec": MyFirstCodec,
"MySecondCodec": MySecondCodec
}
```
## What is the testing strategy for this PR?
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TODO
## Are there any user-facing changes?
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updated before approving the PR.
If there are any breaking changes to public APIs, please add the `api
change` label.
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New `ComposedNamedPhysicalExtensionCodec` is added to the public API, while
keeping the previous `ComposedPhysicalExtensionCodec` still available.
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