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https://issues.apache.org/jira/browse/HIVE-22161?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16919810#comment-16919810
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Gopal V commented on HIVE-22161:
--------------------------------
This was a tiny bit worse than I thought - every single UDF was synchronizing
around the same class objet, UDFType.class
> UDF: FunctionRegistry synchronizes on org.apache.hadoop.hive.ql.udf.UDFType
> class
> ---------------------------------------------------------------------------------
>
> Key: HIVE-22161
> URL: https://issues.apache.org/jira/browse/HIVE-22161
> Project: Hive
> Issue Type: Bug
> Components: UDF
> Reporter: Gopal V
> Assignee: Gopal V
> Priority: Major
> Attachments: HIVE-22161.1.patch
>
>
> There's a hidden synchronization across threads when looking up isStateful
> and isDeterministic.
> https://github.com/apache/hive/blob/master/common/src/java/org/apache/hive/common/util/AnnotationUtils.java#L27
> {code}
> // to avoid https://bugs.openjdk.java.net/browse/JDK-7122142
> public static <T extends Annotation> T getAnnotation(Class<?> clazz,
> Class<T> annotationClass) {
> synchronized (annotationClass) {
> return clazz.getAnnotation(annotationClass);
> }
> }
> {code}
> This is serializing multiple threads initializing UDFs (or checking them
> during compilation) & also being locked across threads for each instance of
> GenericUDFOpEqual in the specific scenario.
> https://bugs.openjdk.java.net/browse/JDK-7122142 is fixed in jdk8+
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