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https://issues.apache.org/jira/browse/LUCENE-3932?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13241548#comment-13241548
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Sean Bridges commented on LUCENE-3932:
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{quote}What %tg of the time is spent on the decode/encode (after fixing the
initial bitEstimate)?{quote}
I've attached a csv of the profiling session. The third column is the
important one.
utf8 -> utf 16 is 7% of the time
utf 16 -> utf8 is 16% of the time
writing vlong's is also 16% of the time, 17% in TermBufer.read() (24% if you
include the call to utf8ToUtf16)
> 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: 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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