The bug of rocksdb env

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- When writing data through the env provided by rocksdb, `NewWritableFile` is called, but `NewRandomAccessFile` is called at the same time. What is the reason?
- Each `NewWritableFile` will actively release resources after the call is completed, but `NewRandomAccessFile` will wait until all writes are completed before releasing resources. This will cause the `NewRandomAccessFile` function to continuously create read objects when the amount of data written is too large. Memory will continue to increase. Has this bug always existed? Is there any solution?