Lucene should have a "write once" mode
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Key: LUCENE-704
URL: http://issues.apache.org/jira/browse/LUCENE-704
Project: Lucene - Java
Issue Type: Improvement
Components: Index
Affects Versions: 2.1
Reporter: Michael McCandless
Assigned To: Michael McCandless
Priority: Minor
This is a spinoff of LUCENE-701
If your directory is residing on a "write once" filesystem (eg Hadoop), we need
for Lucene to have a mode where it doesn't write to the same file more than
once, nor (I think?) do things like rewind a file to overwrite parts of it.
Lockless commits (LUCENE-701 ) gets us closer to this goal because it always
commits to a new segments_N+1 file (and new files for deletes/separate norms),
but, it still re-writes to a "segments.gen" file. This file is often
"optional" (it's only necessary if directory listing can be stale on the
platform/filesystem).
The only other place I know of is in CompoundFileWriter.close(). That method
writes 0's into the header and then rewinds and rewrites those 0s with the
actual offsets into the compound file. I think (on quick inspection) that
pre-computing the offsets and writing everything in one pass should be simple.
Does anyone know of other places that re-use filenames or rewind/seek and
rewrite bytes?
We should create a "setWriteOnceMode()" or something like that.
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