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Clarify the seed value of version #649

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Clarify the seed value of version #649

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14 changes: 13 additions & 1 deletion api/src/main/java/jakarta/persistence/Version.java
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Expand Up @@ -41,14 +41,26 @@
* {@code long}, {@link Long}, {@code java.sql.Timestamp},
* {@link java.time.Instant}, {@link java.time.LocalDateTime}.
*
* <p>This field declares a version number:
* <p>Any <strong>positive number</strong> or <strong>non-null timestamp</strong>
* initial value will be the seed of version, otherwise vendors are free to
* seed the version.
Comment on lines +44 to +46
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I don't see how this actually addresses the real actually-known use case here which is to enable a portable way to choose between an initial version of 0 and an initial version of 1.

With this language:

@Version int version = 1;

lets me portably get an initial value of 1. OK, great.

But:

@Version int version = 0;

Just does something non-portable and vendor-specific.

So there's no portable way to request an initial value of 0.

Is that correct?

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So there's no portable way to request an initial value of 0.

Yes, there is no way to differ int version = 0; from int version;, both of them should be treated as non-predefined, if negative numbers are treated that way, why not zero?

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if negative numbers are treated that way, why not zero?

Well, because counting from 0 is perfectly legit, and often used in computing.

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Indeed, it's what Hibernate does by default, so it can't be terrible.

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if negative numbers are treated that way, why not zero?

Well, because counting from 0 is perfectly legit, and often used in computing.

I'm not against that if EclipseLink team would like to support counting from 0.

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Exactly, so it's something that needs to be discussed properly with @lukasj and we need to think through the full impact. i.e. we need an issue to track this. We can't just make this sort of change as a PR with no discussion.

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we need an issue to track this.

Could you reopen #600?

*
* <p>This field declares a version number, the version seed is vendor-specific:
*
* {@snippet :
* @Version
* @Column(name = "REVISION")
* protected int version;
* }
*
* <p>This field declares a version number, the version seed is <code>1</code> across vendors:
*
* {@snippet :
* @Version
* @Column(name = "REVISION")
* protected int version = 1;
* }
*
* <p>This field declares a revision timestamp:
*
* {@snippet :
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5 changes: 5 additions & 0 deletions spec/src/main/asciidoc/ch02-entities.adoc
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Expand Up @@ -1251,6 +1251,11 @@ hierarchy, or by one of its mapped superclasses. A portable application
must not declare a version field or property in a subclass of the root
class of an entity class hierarchy.

Any *positive number* or *non-null timestamp* initial value will be the seed of version,
otherwise vendors are free to seed the version. A portable application
should declare a version number field with positive initial value
to make the seed deterministic.

=== Basic Types [[a486]]

The following Java types are considered _basic types_:
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