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Posted to issues@solr.apache.org by "Houston Putman (Jira)" <ji...@apache.org> on 2026/03/16 19:07:00 UTC
[jira] [Commented] (SOLR-16989) Optimize and consolidate reuse of DocValues iterators for value retrieval
[ https://issues.apache.org/jira/browse/SOLR-16989?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18066176#comment-18066176 ]
Houston Putman commented on SOLR-16989:
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[~magibney] did you actually record improvements in the case of {{useDocValuesAsStored}}? In the PR you mentioned that there wasn't any improvement for the ExportWriter. And according to SOLR-17539 this really impacts Solr's memory footprint when using {{useDocValuesAsStored}}, so it would be great to know the benefits so we can talk about if the tradeoffs are worth it.
> Optimize and consolidate reuse of DocValues iterators for value retrieval
> -------------------------------------------------------------------------
>
> Key: SOLR-16989
> URL: https://issues.apache.org/jira/browse/SOLR-16989
> Project: Solr
> Issue Type: Improvement
> Affects Versions: 10.0
> Reporter: Michael Gibney
> Assignee: Michael Gibney
> Priority: Major
> Fix For: 9.4
>
> Time Spent: 40m
> Remaining Estimate: 0h
>
> DocValues are used for the purpose of arbitrary-order value retrieval mainly in two places:
> # {{ExportWriter}} (for the export handler)
> # {{SolrDocumentFetcher}} (for {{useDocValuesAsStored}})
> {{ExportWriter}} holds a simple optimization to reuse docValues iterators where possible (i.e., where docId doesn't decrease), but there is no such optimization for {{SolrDocumentFetcher}}: for every possible docValues return field, for every doc, a new docValues iterator is pulled (and GC'd). This is especially pathological in the case of many sparse fields, because the hit is incurred regardless of whether the return fields are actually present in any returned docs.
> This issue proposes unifying the docValues iterator caching for both these contexts, with the most immediate practical effect being improved latency of field retrieval for {{useDocValuesAsStored}}.
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