Erick Erickson created LUCENE-8149:
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Summary: Document why NRTCachingDirectory needs to preemptively
delete segment files.
Key: LUCENE-8149
URL: https://issues.apache.org/jira/browse/LUCENE-8149
Project: Lucene - Core
Issue Type: Improvement
Reporter: Erick Erickson
Assignee: Erick Erickson
Moving over here from SOLR-11892. After getting through my confusion I've found
the following: NRTCachingDirectory.createOutput tries to delete segment files
before creating them. We should at least add a bit of commentary as to what the
pre-emptive delete is there for since on the surface it's not obvious.
try {
in.deleteFile(name);
{{ } catch (IOException ioe) {}}
// This is fine: file may not exist
{{ }}}
If I change to using MMapDirectory or NIOFSDirectory these exceptions are not
thrown. What's special about NRTCachingDirectory that it needs this when two of
the possible underlying FS implementations apparently do not? Or is this
necessary for, say, Windows or file systems than the two I tried? Or is it some
interaction between the RAM based segments and segments on disk?
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