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Posted to commits@fury.apache.org by "LoranceChen (via GitHub)" <gi...@apache.org> on 2024/06/12 04:05:35 UTC
[I] [Scala] support default not-null value in COMPATIBLE mode. [incubator-fury]
LoranceChen opened a new issue, #1683:
URL: https://github.com/apache/incubator-fury/issues/1683
Currently, for scala, add new field and deserialize from old binary data will get a `null` as new field value. But avoid null is a good practice in scala language.
```scala
val personBytes = readBytesFromFile("person_v1") // there are old version `Person(1,true,some text)`
// append field as new person: case class Person(a: Int, b: Boolean, c: String, d: String = "default d")
val deserPerson = fury.deserializeJavaObject(personBytes, classOf[Person])
println(s"deserPerson: ${deserPerson}") // deserPerson: Person(1,true,some text,null)
```
I think it's better using default value our a empty value to set the new field. Such as give the result:
```scala
// deserPerson: Person(1,true,some text, "default d")
```
And if there not a default value in the field define, can give a empty value. For String is `""` will be better for null.
If the new field is a structure, can using a default value to instance this one.
`case class Foo(a: String, b: Int)` can setting the default value as `Foo("", 0)`
However, for some performance care scenario. Using `null` should be better and handler by develop.
I advice add a new configuration to decide using the default value or `null` for new field.
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Re: [I] [Scala] support default not-null value in COMPATIBLE mode. [fury]
Posted by "chaokunyang (via GitHub)" <gi...@apache.org>.
chaokunyang commented on issue #1683:
URL: https://github.com/apache/fury/issues/1683#issuecomment-2171736538
Scala didn't provide a method to construct object with default value at bytecode level. It generate bytecode to invoke constructor with all parameters provided, and default params are provided at callsite.
If we need to provide default value when creating object, we need to extract the default value. Fortunately, scala generate a
method like `SomeClass$.apply$default$2:()I`:
```scala
case class SomeClass(v: List[IdAnyVal], x:Int=1)
// Callsite bytecode
34: getstatic #131 // Field org/apache/fury/serializer/SomeClass$.MODULE$:Lorg/apache/fury/serializer/SomeClass$;
37: invokevirtual #135 // Method org/apache/fury/serializer/SomeClass$.apply$default$2:()I
40: invokespecial #138 // Method org/apache/fury/serializer/SomeClass."<init>":(Lscala/collection/immutable/List;I)V
43: putstatic #87 // Field p:Lorg/apache/fury/serializer/SomeClass;
46: getstatic #143 // Field scala/Predef$.MODULE$:Lscala/Predef$;
```
We may can detect whether such method exists to know which parameter has default value, and provide it as default value when constructing object. This will take some horse work. We don't have time for this currently. Would you like to contribute to this? The `record` contructor in Fury `org.apache.fury.builder.ObjectCodecBuilder#createRecord/org.apache.fury.serializer.ObjectSerializer#read` can be taken as an example.
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Re: [I] [Scala] support default not-null value in COMPATIBLE mode. [fury]
Posted by "chaokunyang (via GitHub)" <gi...@apache.org>.
chaokunyang commented on issue #1683:
URL: https://github.com/apache/fury/issues/1683#issuecomment-2172072000
If the field doesn't exist in serialization process, but does exist in deserialization process, we can invoke method like ` SomeClass$.apply$default$2:()I` to get default value for such field, and set it the object
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Re: [I] [Scala] support default not-null value in COMPATIBLE mode. [fury]
Posted by "LoranceChen (via GitHub)" <gi...@apache.org>.
LoranceChen commented on issue #1683:
URL: https://github.com/apache/fury/issues/1683#issuecomment-2172053408
Hi, great to see can solve it.
Glade to take a PR if possiable and I need sometime to familiar with the repository.
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Re: [I] [Scala] support default not-null value in COMPATIBLE mode. [fury]
Posted by "chaokunyang (via GitHub)" <gi...@apache.org>.
chaokunyang commented on issue #1683:
URL: https://github.com/apache/fury/issues/1683#issuecomment-2516223344
Hi @LoranceChen , are you still working on this issue?
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Re: [I] [Scala] support default not-null value in COMPATIBLE mode. [fory]
Posted by "chaokunyang (via GitHub)" <gi...@apache.org>.
chaokunyang closed issue #1683: [Scala] support default not-null value in COMPATIBLE mode.
URL: https://github.com/apache/fory/issues/1683
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