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https://issues.apache.org/jira/browse/LUCENE-3932?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13242721#comment-13242721
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Sean Bridges commented on LUCENE-3932:
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{quote}Seems like if we made a direct "decode tii file and write in-memory
format" (instead of going through SegmentTermEnum), we could get some of this
back. The vLongs unfortunately need to be decoded/re-encoded because they are
deltas in the file but absolutes in memory. But, eg the vInt docFreq could be a
"copyVInt" method instead of readVInt then writeVInt, which should save a
bit.{quote}
Is the space savings of delta encoding worth the processing time? You could
write the .tii file to disk such that on open you could read it straight into a
byte[]
> Improve load time of .tii files
> -------------------------------
>
> Key: LUCENE-3932
> URL: https://issues.apache.org/jira/browse/LUCENE-3932
> Project: Lucene - Java
> Issue Type: Improvement
> Affects Versions: 3.5
> Environment: Linux
> Reporter: Sean Bridges
> Attachments: LUCENE-3932.trunk.patch, perf.csv
>
>
> We have a large 50 gig index which is optimized as one segment, with a 66 MEG
> .tii file. This index has no norms, and no field cache.
> It takes about 5 seconds to load this index, profiling reveals that 60% of
> the time is spent in GrowableWriter.set(index, value), and most of time in
> set(...) is spent resizing PackedInts.Mutatable current.
> In the constructor for TermInfosReaderIndex, you initialize the writer with
> the line,
> {quote}GrowableWriter indexToTerms = new GrowableWriter(4, indexSize,
> false);{quote}
> For our index using four as the bit estimate results in 27 resizes.
> The last value in indexToTerms is going to be ~ tiiFileLength, and if instead
> you use,
> {quote}int bitEstimate = (int) Math.ceil(Math.log10(tiiFileLength) /
> Math.log10(2));
> GrowableWriter indexToTerms = new GrowableWriter(bitEstimate, indexSize,
> false);{quote}
> Load time improves to ~ 2 seconds.
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