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https://issues.apache.org/jira/browse/SOLR-8096?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15132395#comment-15132395
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Nikolay Khitrin commented on SOLR-8096:
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I can confirm performance issue for new Solr 5.4.1 1725212 with 40M docs index
and 6.7M unique terms per multivalued field.
Facetting takes more than 3 seconds on Solr 5.4.1 and 190ms on Solr 4.4.0 over
near-identical indexes.
My opinion is that DocValues API is JIT-unfriendly. LongValues.get is not
monomorphic call and in single running Solr instance there are at least
DirectMonotonicReader$2 and several DirectReader.DirectPackedReader*
implementations in use.
It is very good approach in OOP terms, but for facetting we need read a lot of
memory (for ex. from memory-mapped inputs) really fast and
SortedSetDocValues-LongValues-RandomAccessInput chain should inline and compile
into simple memory read assembly.
UnInvertedField, itself, is very solid class and can be optimized by JIT really
hard.
> Major faceting performance regressions
> --------------------------------------
>
> Key: SOLR-8096
> URL: https://issues.apache.org/jira/browse/SOLR-8096
> Project: Solr
> Issue Type: Bug
> Affects Versions: 5.0, 5.1, 5.2, 5.3, Trunk
> Reporter: Yonik Seeley
> Priority: Critical
> Attachments: simple_facets.diff
>
>
> Use of the highly optimized faceting that Solr had for multi-valued fields
> over relatively static indexes was removed as part of LUCENE-5666, causing
> severe performance regressions.
> Here are some quick benchmarks to gauge the damage, on a 5M document index,
> with each field having between 0 and 5 values per document. *Higher numbers
> represent worse 5x performance*.
> Solr 5.4_dev faceting time as a percent of Solr 4.10.3 faceting time
> ||...................................|| Percent of index being faceted
> ||num_unique_values|| 10% || 50% || 90% ||
> |10 | 351.17% | 1587.08% | 3057.28% |
> |100 | 158.10% | 203.61% | 1421.93% |
> |1000 | 143.78% | 168.01% | 1325.87% |
> |10000 | 137.98% | 175.31% | 1233.97% |
> |100000 | 142.98% | 159.42% | 1252.45% |
> |1000000 | 255.15% | 165.17% | 1236.75% |
> For example, a field with 1000 unique values in the whole index, faceting
> with 5x took 143% of the 4x time, when ~10% of the docs in the index were
> faceted.
> One user who brought the performance problem to our attention:
> http://markmail.org/message/ekmqh4ocbkwxv3we
> "faceting is unusable slow since upgrade to 5.3.0" (from 4.10.3)
> The disabling of the UnInvertedField algorithm was previously discovered in
> SOLR-7190, but we didn't know just how bad the problem was at that time.
> edit: removed "secret" adverb by request
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