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https://issues.apache.org/jira/browse/AVRO-3257?focusedWorklogId=693503&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-693503
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ASF GitHub Bot logged work on AVRO-3257:
----------------------------------------
Author: ASF GitHub Bot
Created on: 09/Dec/21 19:20
Start Date: 09/Dec/21 19:20
Worklog Time Spent: 10m
Work Description: martin-g commented on a change in pull request #1411:
URL: https://github.com/apache/avro/pull/1411#discussion_r766084596
##########
File path: doc/src/content/xdocs/idl.xml
##########
@@ -301,17 +301,36 @@ record Card {
<section id="unions">
<title>Unions</title>
<p>Union types are denoted as <code>union { typeA, typeB, typeC, ...
}</code>. For example,
- this record contains a string field that is optional (unioned with
<code>null</code>):
+ this record contains a string field that is optional (unioned with
<code>null</code>), and
+ a field containing either a precise or a imprecise number:
</p>
<source>
record RecordWithUnion {
union { null, string } optionalString;
+ union { decimal(12, 6), float } number;
}
</source>
<p>
Note that the same restrictions apply to Avro IDL unions as apply
to unions defined in the
- JSON format; namely, a record may not contain multiple elements of
the same type.
+ JSON format; namely, a record may not contain multiple elements of
the same type. Also,
+ fields/parameters that use the union type and have a default
parameter must specify a
+ default value of the same type as the <em>first</em>em> union type.
</p>
+ <p>Because it occurs so often, there is a special shorthand to
denote a union of
+ <code>null</code> with another type. In the following snippet, the
first three fields have
+ identical types:
+ </p>
+ <source>
+record RecordWithUnion {
+ union { null, string } optionalString1 = null;
+ string? optionalString2 = null;
+ string? optionalString3; // No default value
+ string? optionalString4 = "something";
+}
+ </source>
+ <p>Note that unlike explicit unions, the position of the
<code>null</code> type is fluid; it will be
+ the first or last type depending on the default value (if any). So
in the example above, all fields
+ are valid.</p>
Review comment:
We should not forget to update the new website once it starts being used
(https://lists.apache.org/thread/ktjh7kyd92hf0jsmpp16c3k121dc8grg)
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Issue Time Tracking
-------------------
Worklog Id: (was: 693503)
Time Spent: 1h 40m (was: 1.5h)
> IDL: add syntax to create optional fields
> -----------------------------------------
>
> Key: AVRO-3257
> URL: https://issues.apache.org/jira/browse/AVRO-3257
> Project: Apache Avro
> Issue Type: Improvement
> Components: java, spec
> Reporter: Oscar Westra van Holthe - Kind
> Assignee: Oscar Westra van Holthe - Kind
> Priority: Minor
> Labels: javacc, pull-request-available
> Fix For: 1.11.1
>
> Time Spent: 1h 40m
> Remaining Estimate: 0h
>
> To define optional values, Avro has the "union with the null type"
> construction.
> In IDL, this is a rather verbose construct:
> {code}
> union {null, string} optionalName = null;
> {code}
> Wish: add Kotlin style optional types like this:
> {code}
> string? optionalName = null;
> {code}
> The resulting schema should be identical; it's only a syntax change.
> Note: it would be nice (but not required) if the syntax would also work if
> the default value is not null:
> {code}
> string? optionalName = "Jane Doe";
> {code}
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