Github user manishgupta88 commented on the issue:
https://github.com/apache/carbondata/pull/2898
@xuchuanyin ...your point is correct. To explain this in detail
1. We have already a way to clear the cached DataMaps through API call
`DataMapStoreManager.getInstance().clearDataMaps(AbsoluteTableIdentifier
identifier)`. This API call ensures that for a given table all the dataMaps are
cleared.
2. For FileFormat case if the above API is not integrated by the customer
there is a possibility that drop table call will not come to carbondata layer
and there can be few stale objects which can cause query failure.
The PR is raised to handle the 2nd case. The other stale DataMaps are being
already taken care by the LRU cache which will clear the stale entries one LRU
cache threshold is reached.
Let me know if you still have doubts
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