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https://issues.apache.org/jira/browse/AVRO-4093?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17901598#comment-17901598
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Huw Campbell edited comment on AVRO-4093 at 11/27/24 10:54 PM:
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Personally I think the change to the specification should be reverted.
It's not safe, and means that valid schemas don't round trip anymore (I have
property tests in my Haskell library which can not be made to pass, I'm sure
other libraries will find this when they implement it).
Remember that Avro has an encoding for JSON objects which properly supports
union types, e.g., \{ "int": 2 }.
was (Author: JIRAUSER306745):
Personally I think the change to the specification should be reverted.
It's not safe, and means that valid schemas don't round trip anymore (I have
property tests in my Haskell library which can not be made to pass, I'm sure
other libraries will find this when they implement it).
Remember that Avro has an encoding for JSON objects which properly supports
union types, e.g., \{ "int": 2 }. At the very, very least, using that could be
supported in the default position for a union (and I would recommend it be
required if the value is not from the first position).
> New union defaulting rules is dangerous.
> ----------------------------------------
>
> Key: AVRO-4093
> URL: https://issues.apache.org/jira/browse/AVRO-4093
> Project: Apache Avro
> Issue Type: Bug
> Components: spec
> Affects Versions: 1.12.0
> Reporter: Huw Campbell
> Priority: Major
>
> {{In version 1.12, the specification for unions changed, so that the default
> value must be one of the values instead of the first one.}}
> {{While this sounds ok at first blush, it opens a whole kettle of worms with
> regards to schemas which appear correct but contain bugs.}}
> {{For example, this schema has four examples which I want defaults for, in
> all cases, I want the second one, but the first will be picked.}}
>
> {color:#a31515}{ "type": "record"{color}
> {color:#a31515}, "name": "demo1"{color}
> {color:#a31515}, "fields" :{color}
> {color:#a31515} [ { "name": "enum"{color}
> {color:#a31515} , "type":{color}
> {color:#a31515} [ \{ "type": "enum", "name": "suit", "symbols": [ "diamonds",
> "hearts", "clubs", "spades" ] }{color}
> {color:#a31515} , \{ "type": "enum", "name": "tools", "symbols": [ "shovels",
> "spades", "hammers", "drills" ] }{color}
> {color:#a31515} ]{color}
> {color:#a31515} , "doc": "I want tools to be the default, but if I select
> spades we get a suit!"{color}
> {color:#a31515} , "default": "spades"{color}
> {color:#a31515} }{color}
> {color:#a31515} , { "name": "string_enum"{color}
> {color:#a31515} , "type":{color}
> {color:#a31515} [ \{ "type": "string" }{color}
> {color:#a31515} , \{ "type": "enum", "name": "tools", "symbols": [ "shovels",
> "spades", "hammers", "drills" ] }{color}
> {color:#a31515} ]{color}
> {color:#a31515} , "doc": "I want tools to be the default, but this will be a
> string"{color}
> {color:#a31515} , "default": "drill"{color}
> {color:#a31515} }{color}
> {color:#a31515} , { "name": "int_long"{color}
> {color:#a31515} , "type": [ "int", "long"]{color}
> {color:#a31515} , "doc": "I can't make this a long"{color}
> {color:#a31515} , "default": 400000000{color}
> {color:#a31515} }{color}
> {color:#a31515} , { "name": "records_ambiguity"{color}
> {color:#a31515} , "type":{color}
> {color:#a31515} [ { "name": "xs"{color}
> {color:#a31515} , "type":{color}
> {color:#a31515} { "type": "record"{color}
> {color:#a31515} , "name": "xs"{color}
> {color:#a31515} , "fields" : [ \{ "name": "z", "type": [ "null", "int" ],
> "default": null }, \{ "name": "w", "type": [ "null", "int" ], "default": null
> } ]{color}
> {color:#a31515} }{color}
> {color:#a31515} }{color}
> {color:#a31515} , { "name": "ys"{color}
> {color:#a31515} , "type":{color}
> {color:#a31515} { "type": "record"{color}
> {color:#a31515} , "name": "ys"{color}
> {color:#a31515} , "fields" : [ \{ "name": "a", "type": "int" } , \{ "name":
> "c", "type": "string" } ]{color}
> {color:#a31515} }{color}
> {color:#a31515} }{color}
> {color:#a31515} ]{color}
> {color:#a31515} , "doc": "I want ys, hence the fields a and c, xs has
> everything with defaults, so it matches and the items are discarded."{color}
> {color:#a31515} , "default": \{ "a": 2, "c": "yes" }{color}
> {color:#a31515} }{color}
> {color:#a31515} ]{color}
> {color:#a31515}}
>
> {{Other things which it can get wrong are "fixed", fields which have names,
> so two are fine, but they could be parsed as each other, "bytes", and so on.}}
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