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https://issues.apache.org/jira/browse/LUCENE-7317?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15426601#comment-15426601
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Ferenczi Jim commented on LUCENE-7317:
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I wanted to see what we're loosing with the removal of the AutoPrefix so I ran
a small test with English Wikipedia title.
I indexed the 12M titles in three indices:
* *default*: keyword analyzer and the default postings format
* *auto_prefix*: keyword analyzer and the AutoPrefixPostings format with
minAutoPrefix=24, maxAutoPrefix=Integer.MAX
* *edge*: edge ngram analyzer with minGram=1,maxGram=Integer.MAX and the
default postings format.
||index||default||auto_prefix||edge||
||size in MB||231MB||274 MB||1600MB||
This table shows the size that each index takes on disk in bytes. As you can
see the auto_prefix is very close to the size of the default one even though we
compute all the prefix with more than 24 terms. Compared to the edge_ngram
which multiplies the index size by a factor 7, the auto prefix seems to be a
good trade off for fields where prefix queries are the norm. I didn't compare
the query time but any prefix with more than 24 terms could be resolved by one
inverted list in the auto_prefix index so it is equivalent to the edge_ngram
index.
The downside of the auto_prefix seems to be the merge, it takes more than 1
minute to optimize, this is 10 times slower than the default index. Though this
is expected since the default index uses a keyword analyzer.
I understand that the new points APIs is better for numeric prefix/range
queries but the auto prefix seems to be a good fit for prefix string queries.
It saves a lot of spaces compared to edge ngram and the indexation is faster. I
am not saying we should restore the functionality inside the default
BlockTreeTerms but maybe we could create a separate postings format that
exposes this feature ?
> Remove auto prefix terms
> ------------------------
>
> Key: LUCENE-7317
> URL: https://issues.apache.org/jira/browse/LUCENE-7317
> Project: Lucene - Core
> Issue Type: Task
> Reporter: Adrien Grand
> Priority: Minor
> Fix For: master (7.0), 6.2
>
> Attachments: LUCENE-7317.patch
>
>
> This was mostly superseded by the new points API so should we remove
> auto-prefix terms?
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