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https://issues.apache.org/jira/browse/LUCENE-9674?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17270750#comment-17270750
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Michael Sokolov commented on LUCENE-9674:
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Checking luceneutil, that does not surprise me. At some point I had added
support for retrieval of vectors (as we had done previously for stored fields),
which would in theory exercise this API. KNN search does not exercise it - it
uses only the random access API, not the forward iterator (nextDoc) that was
optimized here.
It would be nice to measure the impact, but I think we had disabled this
previously since turning it on would impact *all* tasks, not just the vector
tasks. At the same time I see that the way this was implemented *also* uses the
random access API, although it should not. My past self was not thinking
clearly. In SearchTask we added vector retrieval for tasks
https://github.com/mikemccand/luceneutil/blob/master/src/main/perf/SearchTask.java#L312
but the way it is done will retrieve the vector for the wrong doc as it is
using the docid to retrieve from the ordinal API.
So -- we should fix that last issue and see if we can measure the impact of
this change, and then maybe we can find a way to control this per-task?
> Faster advance on Vector Values
> -------------------------------
>
> Key: LUCENE-9674
> URL: https://issues.apache.org/jira/browse/LUCENE-9674
> Project: Lucene - Core
> Issue Type: Improvement
> Components: core/codecs
> Affects Versions: master (9.0)
> Environment:
> Reporter: Anand Kotriwal
> Priority: Major
> Time Spent: 4h
> Remaining Estimate: 0h
>
> The advance() function in the class Lucene90VectorReader does a linear search
> for the target document.
> To make it faster we can do a binary search over the "ordToDoc" array which
> will make the advance operation take logarithmic time to search.This will
> make retrieving vectors for a sparse set of documents efficient.
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