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Posted to issues@lucene.apache.org by "weizijun (Jira)" <ji...@apache.org> on 2021/08/26 06:54:00 UTC
[jira] [Updated] (LUCENE-10033) Encode doc values in smaller blocks
of values, like postings
[ https://issues.apache.org/jira/browse/LUCENE-10033?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
weizijun updated LUCENE-10033:
------------------------------
Attachment: benchmark
> Encode doc values in smaller blocks of values, like postings
> ------------------------------------------------------------
>
> Key: LUCENE-10033
> URL: https://issues.apache.org/jira/browse/LUCENE-10033
> Project: Lucene - Core
> Issue Type: Improvement
> Reporter: Adrien Grand
> Priority: Minor
> Attachments: benchmark
>
> Time Spent: 1h
> Remaining Estimate: 0h
>
> This is a follow-up to the discussion on this thread: https://lists.apache.org/thread.html/r7b757074d5f02874ce3a295b0007dff486bc10d08fb0b5e5a4ba72c5%40%3Cdev.lucene.apache.org%3E.
> Our current approach for doc values uses large blocks of 16k values where values can be decompressed independently, using DirectWriter/DirectReader. This is a bit inefficient in some cases, e.g. a single outlier can grow the number of bits per value for the entire block, we can't easily use run-length compression, etc. Plus, it encourages using a different sub-class for every compression technique, which puts pressure on the JVM.
> We'd like to move to an approach that would be more similar to postings with smaller blocks (e.g. 128 values) whose values get all decompressed at once (using SIMD instructions), with skip data within blocks in order to efficiently skip to arbitrary doc IDs (or maybe still use jump tables as today's doc values, and as discussed here for postings: https://lists.apache.org/thread.html/r7c3cb7ab143fd4ecbc05c04064d10ef9fb50c5b4d6479b0f35732677%40%3Cdev.lucene.apache.org%3E).
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