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https://issues.apache.org/jira/browse/SOLR-2026?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12899254#action_12899254
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Lance Norskog edited comment on SOLR-2026 at 8/16/10 10:49 PM:
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About where in the stack this should occur: I can wanting to do 2 successive
queries at each shard, or doing one query against all shards, then a second
query against shards. These would be implemented in different parts of the
code stack, right?
was (Author: lancenorskog):
Here's a use case: field collapsing. Some people currently do field
collapsing with 2 queries: first you get a few hundred documents with just the
id and _collapsar_ field. Then you trim the id set from the collapsar contents.
and grab the first N unique ids. This is fine when you don't really care how
many docs are in each collapsar group, you only care that there is more than
one item per group.
This works great as a 2-query sequence where the code analyses the first return
to create the second query.
> Need infrastructure support in Solr for requests that perform multiple
> sequential queries
> -----------------------------------------------------------------------------------------
>
> Key: SOLR-2026
> URL: https://issues.apache.org/jira/browse/SOLR-2026
> Project: Solr
> Issue Type: New Feature
> Components: SearchComponents - other
> Reporter: Karl Wright
> Assignee: Simon Willnauer
> Priority: Minor
> Fix For: 4.0
>
> Attachments: SOLR-2026.patch, SOLR-2026.patch
>
>
> Several known cases exist where multiple index searches need to be performed
> in order to arrive at the final result. Typically, these have the constraint
> that the results from one search query are required in order to form a
> subsequent search query. While it is possible to write a custom
> QueryComponent or search handler to perform this task, an extension to the
> SearchHandler base class would readily permit such query sequences to be
> configured using solrconfig.xml.
> I will be therefore writing and attaching a patch tomorrow morning which
> supports this extended functionality in a backwards-compatible manner. The
> tricky part, which is figuring out how to funnel the output of the previous
> search result into the next query, can be readily achieved by use of the
> SolrRequestObject.getContext() functionality. The stipulation will therefore
> be that the SolrRequestObject's lifetime will be that of the entire request,
> which makes complete sense. (The SolrResponseObject's lifetime will, on the
> other hand, be limited to a single query, and the last response so formed
> will be what gets actually returned by SearchHandler.)
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