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https://issues.apache.org/jira/browse/SOLR-9550?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18132111#comment-18132111
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Nick Shanin commented on SOLR-9550:
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>From code reading against apache/main b73f03976fa, `InnerJoinStream` does not
>check that its input is sorted
>(solr/solrj-streaming/src/java/org/apache/solr/client/solrj/io/stream/InnerJoinStream.java:63-73).
> A candidate is to throw when a side's tuples are out of order. Is an error
>the behaviour you want?
🤖 AI-generated 🤖
> innerJoin can succeed with bad sorting
> --------------------------------------
>
> Key: SOLR-9550
> URL: https://issues.apache.org/jira/browse/SOLR-9550
> Project: Solr
> Issue Type: Bug
> Components: SolrCloud
> Affects Versions: 6.1
> Environment: CentOS 6.8, OpenJDK 1.8
> Reporter: Stuart Bertram
> Priority: Major
>
> The innerJoin streaming function requires that both streams are ordered by
> the correct keys for joining. In some situations, you can make a mistake and
> use an incorrect sort order but get a successful (but incorrect) return.
> Example:
> * Collection "UserPosts" has columns: ID, ByUserID
> * Collection "User" has columns: ID, Username, Registered, …
> * Streaming query {{gatherNodes(User, gatherNodes(UserPosts, walk="42
> 69->ID", gather="ByUserID"), walk="node->ID", gather="ID")}} returns the IDs
> of users who made posts 42 and 69, but we want the full user details
> * Streaming query {{innerJoin(sort(gatherNodes(User, gatherNodes(UserPosts,
> walk="42 69->ID", gather="ByUserID"), walk="node->ID", gather="ID"), by="ID
> asc"), search(User,qt="/export",q="*:*",fl="ID, Username, Registered, …",
> sort="ID asc"), on="node=ID")}} (Note the {{sort(…, by="ID")}}, because we're
> gathering the ID field, instead of {{sort(…, by="node")}}, because the
> gathered nodes return a tuple with the gathered ID in the "node" field)
> (Note: This example is simplified, so while there may be a better way to
> perform this specific query, the concept and the underlying issue remains)
> Expected result: Solr throws a (useful) exception saying that the sort orders
> do not match the join (because the first stream is sorted by ID, but the join
> is *node*=ID), as it does if the sort() call wasn't included.
> Actual result: Solr believes the queries are correctly sorted and returns
> each node from the first set joined with one set of values chosen from the
> second stream (each row is joined to the *same* row), so the returned ID and
> node values do not match, despite them being used in the join equality.
> This seems like a simple mistake to make at first, as I was gathering IDs and
> so automatically tried to sort by ID, but should have sorted by node.
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