uschindler commented on issue #758: LUCENE-8833: Add a #load() method to IndexInput to allow preloading file content into physical memory URL: https://github.com/apache/lucene-solr/pull/758#issuecomment-521674174 > I am still in review (have to feed my brain with all details, reading C++ source code of JVM and so on). > > Because of Adrien's comment you changed the slice building to also take the start position into account, so the slice method returns a byte buffer that is really only a view and a call to load() would not read data of the whole CFS file. > > As you changed this method to take care of the start offset/position, please fix the javadocs comment: > > ``` > /** Returns a sliced view from a set of already-existing buffers: > * the last buffer's limit() will be correct, but > * you must deal with offset separately (the first buffer will not be adjusted) */ > private ByteBuffer[] buildSlice(ByteBuffer[] buffers, long offset, long length) { > ``` I am not fully sure how the comment would look like. Currently it only fixes the start offset for single-buffer indexinputs. The code is horrible here, I still don't fully understand the code difference for single and multi buffer indexinputs. IMHO, we should change the code and make buildSlice always fix position() and limit() and build a buffer slice for the first and last buffer. How it's done currently is hard to understand. I cannot make any guarantees that the code behaves correctly after this patch and I am not sure if testing of all cases is fine. Maybe only apply to master first and let Jenkins test it.
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