[jira] [Commented] (SOLR-4905) Cross core joins don't work for SolrCloud collections and/or aliases

["Chris Toomey (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SOLR-4905?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13697400#comment-13697400 ] 

Chris Toomey commented on SOLR-4905:
------------------------------------

I've been experimenting with cross-core joins in SolrCloud and found that this problem does indeed occur when the collection being joined is created via the collections API.  Solr returns the error "Cross-core join: no such core <fromIndex name>".

But if the collection being joined is created at bootstrap time, cross-core join does work and doesn't give that error.

So the bug must be somewhere in how the collection create command is implemented, such that the join plugin doesn't find created collection's core?  But even if it worked as is, the fact that the collection create command names the created cores "<collectionName>_shard<x>_replica<y>" instead of "<collectionName>" would prevent this from working across multiple nodes (like 2 replicas) since the fromIndex name is different on each node.  So it seems that naming convention should be changed, agreed?  Should I file a separate bug on that?

My use case is where the collection being joined is small and doesn't need to be sharded, but the "outer" collection may be large and need to be sharded.  So even without distributed joins, this should work, since the collection being joined would be replicated to each node and hence both cores being joined would be on the same node (for each shard of the outer collection).  And like I say, it *does* work when all the collections are configured/created at bootstrap time.  The problem there is that there's only a single numShards param. which applies to every bootstrapped collection, so having the outer collection sharded and the inner one not isn't possible.

                
> Cross core joins don't work for SolrCloud collections and/or aliases
> --------------------------------------------------------------------
>
>                 Key: SOLR-4905
>                 URL: https://issues.apache.org/jira/browse/SOLR-4905
>             Project: Solr
>          Issue Type: Improvement
>          Components: SolrCloud
>            Reporter: Philip K. Warren
>
> Using a non-SolrCloud setup, it is possible to perform cross core joins (http://wiki.apache.org/solr/Join). When testing with SolrCloud, however, neither the collection name, alias name (we have created aliases to SolrCloud collections), or the automatically generated core name (i.e. <collection>_shard1_replica1) work as the fromIndex parameter for a cross-core join.

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