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https://issues.apache.org/jira/browse/HIVE-11288?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14644736#comment-14644736
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Swarnim Kulkarni commented on HIVE-11288:
-----------------------------------------
{quote}
The instanceCache could probably be a singleton, and shouldn't really require
an equals method (unless I am mistaken).
{quote}
If I am not missing something, I think that is a dangerous assumption to make.
Mostly because currently there is nothing on the InstanceCache that states that
it should be used as a singleton[1]. So I would vote that we either
specifically mark that by making the constructor on the class private or
implement hashcode and equals on the class. Also could be nice to mark those
final so that we do not have bad overrides of those?
[1]
https://github.com/apache/hive/blob/master/serde/src/java/org/apache/hadoop/hive/serde2/avro/InstanceCache.java#L38
> Avro SerDe InstanceCache returns incorrect schema
> -------------------------------------------------
>
> Key: HIVE-11288
> URL: https://issues.apache.org/jira/browse/HIVE-11288
> Project: Hive
> Issue Type: Bug
> Reporter: Greg Phillips
> Assignee: Greg Phillips
> Attachments: HIVE-11288.2.patch, HIVE-11288.3.patch,
> HIVE-11288.4.patch, HIVE-11288.patch
>
>
> To reproduce this error, take two fields in an avro schema document matching
> the following:
> "type" : { "type": "array", "items": [ "null", { "type": "map", "values": [
> "null", "string" ] } ] }
> "type" : { "type": "map", "values": [ "null" , { "type": "array", "items": [
> "null" , "string"] } ] }
> After creating two tables in hive with these schemas, the describe statement
> on each of them will only return the schema for the first one loaded. This
> is due to a hashCode() collision in the InstanceCache.
> A patch will be included in this ticket shortly which removes the hashCode
> call from the InstanceCache's internal HashMap, and instead provides the
> entire schema object.
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