Robert Muir created LUCENE-9480:
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Summary: investigate slow DataInput.skipBytes
Key: LUCENE-9480
URL: https://issues.apache.org/jira/browse/LUCENE-9480
Project: Lucene - Core
Issue Type: Improvement
Reporter: Robert Muir
Currently DataInput has skipBytes(), but IndexInput also adds seek().
There isn't a clear reason about the differences in the two methods: why would
you choose one over the other?
It causes some performance issues: for example the default implementation
actually reads bytes into a byte array and throws everything away. This is
really silly for MMapDirectory: skipping bytes should only be a glorified
{{+=}}.
So when I look at latest LUCENE-9447 patch, I can't help but think a ton of
waste is happening:
* Maybe skipBytes() is only used because the stored fields compressor interface
happens to take DataInput? Should it take IndexInput instead?
* Should skipBytes() be overridden by MMapDirectory rather than delegating to
super? doing real reads and byte array copies isn't free. It should be a {{+=}}
with single bounds check.
* Should we revisit having DataInput vs IndexInput at all? Maybe they should be
collapsed into one thing?
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