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https://issues.apache.org/jira/browse/LUCENE-9663?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17268982#comment-17268982
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Jaison.Bi commented on LUCENE-9663:
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{quote}In future tests you could ask Lucene to disable compound file format.
{quote}
ok:)
{quote}But, building the {{OrdinalMap}} got quite a bit slower in some cases,
if I'm reading the above table correctly? E.g. ~1.2 seconds to ~2.1 seconds
for field {{extend}}? But other fields were less heavily impacted.
{quote}
correct. The average value size of field "extend" is bigger than others. So
bigger value size indicates more decompression overhead.
{quote}This is likely an OK tradeoff – we pay that slower price once per
refresh, but gain a substantially smaller index for text heavy / high
cardinality SSDV fields.
{quote}
So this feature is only enabled under BEST_COMPRESSION mode currently.
Thanks [~mikemccand]
> Adding compression to terms dict from SortedSet/Sorted DocValues
> ----------------------------------------------------------------
>
> Key: LUCENE-9663
> URL: https://issues.apache.org/jira/browse/LUCENE-9663
> Project: Lucene - Core
> Issue Type: Improvement
> Components: core/codecs
> Reporter: Jaison.Bi
> Priority: Trivial
> Time Spent: 10m
> Remaining Estimate: 0h
>
> Elasticsearch keyword field uses SortedSet DocValues. In our applications,
> “keyword” is the most frequently used field type.
> LUCENE-7081 has done prefix-compression for docvalues terms dict. We can do
> better by replacing prefix-compression with LZ4. In one of our application,
> the dvd files were ~41% smaller with this change(from 1.95 GB to 1.15 GB).
> I've done simple tests based on the real application data, comparing the
> write/merge time cost, and the on-disk *.dvd file size(after merge into 1
> segment).
> || ||Before||After||
> |Write time cost(ms)|591972|618200|
> |Merge time cost(ms)|270661|294663|
> |*.dvd file size(GB)|1.95|1.15|
> This feature is only for the high-cardinality fields.
> I'm doing the benchmark test based on luceneutil. Will attach the report and
> patch after the test.
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