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https://issues.apache.org/jira/browse/AVRO-853?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13061446#comment-13061446
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Scott Carey commented on AVRO-853:
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{quote}
I think we have two consistent choices:
* Schemas are equal only if all aliases, props, and doc fields match exactly –
in other words if toString() prints the same result.
* Schemas are equal based on name, type, and structure alone. In other words,
they can exchange serialized data without type promotion.
{quote}
I want to discuss this point a bit more. These in my mind are the two
fundamental use cases for equivalence of schemas:
* In their JSON form, do they contain the same information? (requires
checking props, aliases, and doc)
or
* Can these two schemas participate in a bi-directional exchange of serialized
information according to the Avro spec? (requires ignoring props, aliases, and
doc)
Type promotion in schema resolution cannot be part of equals() because it is
asymmmetric. {"int"} promotesTo {"long"} but not vice-versa. Like alias
translation, this is a separate question and not one of equivalence. Type
promotion is one-way, alias translation is two-way but not transitive.
> Cache hash codes in Schema and Field
> ------------------------------------
>
> Key: AVRO-853
> URL: https://issues.apache.org/jira/browse/AVRO-853
> Project: Avro
> Issue Type: Improvement
> Components: java
> Affects Versions: 1.5.1
> Reporter: Douglas Kaminsky
> Attachments: AVRO-853-approach2.patch, AVRO-853.patch
>
>
> We are experiencing a serious performance degradation when trying to
> store/retrieve fields and schemas in hash-based data structures (eg.
> HashMap). Since all fields and schemas are immutable (with the exception of
> RecordSchema allowing deferred setting of Fields) it makes sense to cache the
> hash code on the object instead of recalculating every time the hashCode
> method gets called.
> (Are there other mutable Schema sub-types that I'm not thinking about?)
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