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https://issues.apache.org/jira/browse/LUCENE-9378?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17234755#comment-17234755
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Adrien Grand commented on LUCENE-9378:
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[~gworah] I'm pretty sure that the drop is due to this change as we had seen a
change in the other direction when introducing compression for binary fields.
The format with compression looks generally faster for linear scans (like our
faceting tasks in nightlies) and slower for selective queries (like some
use-cases mentioned above).
> Configurable compression for BinaryDocValues
> --------------------------------------------
>
> Key: LUCENE-9378
> URL: https://issues.apache.org/jira/browse/LUCENE-9378
> Project: Lucene - Core
> Issue Type: Improvement
> Reporter: Viral Gandhi
> Priority: Major
> Fix For: 8.8
>
> Attachments: hotspots-v76x.png, hotspots-v76x.png, hotspots-v76x.png,
> hotspots-v76x.png, hotspots-v76x.png, hotspots-v77x.png, hotspots-v77x.png,
> hotspots-v77x.png, hotspots-v77x.png, image-2020-06-12-22-17-30-339.png,
> image-2020-06-12-22-17-53-961.png, image-2020-06-12-22-18-24-527.png,
> image-2020-06-12-22-18-48-919.png, snapshot-v77x.nps, snapshot-v77x.nps,
> snapshot-v77x.nps, snapshots-v76x.nps, snapshots-v76x.nps, snapshots-v76x.nps
>
> Time Spent: 5h 40m
> Remaining Estimate: 0h
>
> Lucene 8.5.1 includes a change to always [compress
> BinaryDocValues|https://issues.apache.org/jira/browse/LUCENE-9211]. This
> caused (~30%) reduction in our red-line QPS (throughput).
> We think users should be given some way to opt-in for this compression
> feature instead of always being enabled which can have a substantial query
> time cost as we saw during our upgrade. [~mikemccand] suggested one possible
> approach by introducing a *mode* in Lucene80DocValuesFormat (COMPRESSED and
> UNCOMPRESSED) and allowing users to create a custom Codec subclassing the
> default Codec and pick the format they want.
> Idea is similar to Lucene50StoredFieldsFormat which has two modes,
> Mode.BEST_SPEED and Mode.BEST_COMPRESSION.
> Here's related issues for adding benchmark covering BINARY doc values
> query-time performance - [https://github.com/mikemccand/luceneutil/issues/61]
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