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https://issues.apache.org/jira/browse/LUCENE-843?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12486334
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Michael McCandless commented on LUCENE-843:
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Here are the results for "normal" sized docs (1K tokens = ~5,500 bytes plain
text each):
200000 DOCS @ ~5,500 bytes plain text
RAM = 32 MB
NUM THREADS = 1
MERGE FACTOR = 10
No term vectors nor stored fields
AUTOCOMMIT = true (commit whenever RAM is full)
old
200000 docs in 397.6 secs
index size = 415M
new
200000 docs in 167.5 secs
index size = 411M
Total Docs/sec: old 503.1; new 1194.1 [ 137.3% faster]
Docs/MB @ flush: old 81.6; new 406.2 [ 397.6% more]
Avg RAM used (MB) @ flush: old 87.3; new 35.2 [ 59.7% less]
AUTOCOMMIT = false (commit only once at the end)
old
200000 docs in 394.6 secs
index size = 415M
new
200000 docs in 168.4 secs
index size = 408M
Total Docs/sec: old 506.9; new 1187.7 [ 134.3% faster]
Docs/MB @ flush: old 81.6; new 432.2 [ 429.4% more]
Avg RAM used (MB) @ flush: old 126.6; new 36.9 [ 70.8% less]
With term vectors (positions + offsets) and 2 small stored fields
AUTOCOMMIT = true (commit whenever RAM is full)
old
200000 docs in 754.2 secs
index size = 1.7G
new
200000 docs in 304.9 secs
index size = 1.7G
Total Docs/sec: old 265.2; new 656.0 [ 147.4% faster]
Docs/MB @ flush: old 46.7; new 406.2 [ 769.6% more]
Avg RAM used (MB) @ flush: old 92.9; new 35.2 [ 62.1% less]
AUTOCOMMIT = false (commit only once at the end)
old
200000 docs in 743.9 secs
index size = 1.7G
new
200000 docs in 244.3 secs
index size = 1.7G
Total Docs/sec: old 268.9; new 818.7 [ 204.5% faster]
Docs/MB @ flush: old 46.7; new 432.2 [ 825.2% more]
Avg RAM used (MB) @ flush: old 93.0; new 36.6 [ 60.6% less]
> improve how IndexWriter uses RAM to buffer added documents
> ----------------------------------------------------------
>
> Key: LUCENE-843
> URL: https://issues.apache.org/jira/browse/LUCENE-843
> Project: Lucene - Java
> Issue Type: Improvement
> Components: Index
> Affects Versions: 2.2
> Reporter: Michael McCandless
> Assigned To: Michael McCandless
> Priority: Minor
> Attachments: LUCENE-843.patch, LUCENE-843.take2.patch,
> LUCENE-843.take3.patch, LUCENE-843.take4.patch
>
>
> I'm working on a new class (MultiDocumentWriter) that writes more than
> one document directly into a single Lucene segment, more efficiently
> than the current approach.
> This only affects the creation of an initial segment from added
> documents. I haven't changed anything after that, eg how segments are
> merged.
> The basic ideas are:
> * Write stored fields and term vectors directly to disk (don't
> use up RAM for these).
> * Gather posting lists & term infos in RAM, but periodically do
> in-RAM merges. Once RAM is full, flush buffers to disk (and
> merge them later when it's time to make a real segment).
> * Recycle objects/buffers to reduce time/stress in GC.
> * Other various optimizations.
> Some of these changes are similar to how KinoSearch builds a segment.
> But, I haven't made any changes to Lucene's file format nor added
> requirements for a global fields schema.
> So far the only externally visible change is a new method
> "setRAMBufferSize" in IndexWriter (and setMaxBufferedDocs is
> deprecated) so that it flushes according to RAM usage and not a fixed
> number documents added.
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