mythrocks commented on a change in pull request #807:
URL: https://github.com/apache/hive/pull/807#discussion_r434739477
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File path: serde/src/java/org/apache/hadoop/hive/serde2/avro/InstanceCache.java
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@@ -51,20 +51,19 @@ public Instance retrieve(SeedObject hv) throws
AvroSerdeException {
* Retrieve (or create if it doesn't exist) the correct Instance for this
* SeedObject using 'seenSchemas' to resolve circular references
*/
- public synchronized Instance retrieve(SeedObject hv,
- Set<SeedObject> seenSchemas) throws AvroSerdeException {
+ public Instance retrieve(SeedObject hv, Set<SeedObject> seenSchemas)
+ throws AvroSerdeException {
if(LOG.isDebugEnabled()) LOG.debug("Checking for hv: " + hv.toString());
if(cache.containsKey(hv)) {
Review comment:
I had left [a comment about this on
HIVE-19261](https://issues.apache.org/jira/browse/HIVE-19261?focusedCommentId=16929610&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-16929610).
I think `makeInstance()` makes reentrant calls into
`InstanceCache::retrieve()`.
`computeIfAbsent()` expects that `cache` not be modified in the lambda.
Calling calling `makeInstance()` from `computeIfAbsent()` might lead to a
hang. I ran into this when testing an older version of this patch, some months
ago.
It's possible that the reentrant call no longer occurs. I'd check this
before using `computeIfAbsent()`.
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