[RocksJava] Allow iterators to be refreshed with new data #3465
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| void Java_org_rocksdb_WBWIRocksIterator_refresh0( | ||
| JNIEnv* env, jobject jobj, jlong handle) { | ||
| auto* it = reinterpret_cast<rocksdb::Iterator*>(handle); |
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Note the cast to rocksdb::Iterator here instead of rocksdb::WBWIIterator, so that we can use the default implementation and return Status::NotSupported.
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I don't see WBWIIterator to be a child class of Iterator. I don't know how this can be casted.
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I guess you are right. This seems like a blunder on my part. Thanks for catching this.
RocksIterator and WBWIRocksIterator inherit from AbstractRocksIterator/RocksInterface on the java side, but they don't have such an inheritance chain on the C++ side, which contributed to the confusion at my end.
I need to re-think the strategy for WBWIRockIterator ... may be something like just throwing a RocksDBException from Java layer without even going to the C++ layer.
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Otherwise LGTM |
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| return; | ||
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| rocksdb::RocksDBExceptionJni::ThrowNew(env, s); |
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@sagar0 if you delete line 549 to line 554, and only leave 556 with a NotSupported message, I can merge it.
We need you advice on how we should do with it.
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Any news on this? I was going to open the same exact PR but noticed this - I'd love to get access to |
Summary: This PR exposes the `Iterator::Refresh` method to the Java API by adding it on the `RocksIteratorInterface` interface. There are three concrete implementations: `RocksIterator`, `SstFileReaderIterator`, and `WBWIRocksIterator`. For the first two cases, the JNI side simply delegates to the underlying `Iterator::Refresh` method; in the last case, as it doesn't share an ancestor, and per the discussion in #3465, a `Status::NotSupported` exception is thrown. As the last PR had no activity in a while, I'm opening a new one - I'm completely fine with merging the previous PR if it gets completed before this is reviewed. Let me know if there's anything missing or anything else I can do 👍 Pull Request resolved: #6573 Reviewed By: cheng-chang Differential Revision: D20604666 Pulled By: pdillinger fbshipit-source-id: 4de17df1180c3b87b76cfdd77b674b81fc0563f7
Ported Iterator::Refresh functionality to RocksJava. This was originally introduced in the C++ API by @siying in #2621.
This should reduce GC pressure particularly in use-cases that frequently create and destroy large number of iterators just to get to the latest snapshot of data.
The API can be invoked by calling
RocksIterator::refresh().WBWIRocksIterator::refresh()is not implemented and would throw a not-supported exception for now.Test Plan:
Added Unit tests.