[teiid-issues] [JBoss JIRA] (TEIID-2363) proactive buffering not occurring for the inner side of an outer join on "MERGE JOIN (SORT/ALREADY_SORTED)"

[Steven Hawkins (JIRA)]

    [ https://issues.jboss.org/browse/TEIID-2363?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12750846#comment-12750846 ] 

Steven Hawkins commented on TEIID-2363:
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I need to refine my earlier comments on this.  The situation that should be automatically handled is a non-dependent MERGE JOIN (SORT/SORT) - since both sides will require buffering and may proceed independently.  In this case, with the inner side being ALREADY_SORTED - the logic regardless will prefer to stream those values in rather than buffering them (which is the caveat I'm mentioning above).  The approach there may be to do proactive fetching/buffering proportional to the amount of times the left side is blocking, but then process the buffer down while performing the join. 
                
> proactive buffering not occurring for the inner side of an outer join on "MERGE JOIN (SORT/ALREADY_SORTED)"
> -----------------------------------------------------------------------------------------------------------
>
>                 Key: TEIID-2363
>                 URL: https://issues.jboss.org/browse/TEIID-2363
>             Project: Teiid
>          Issue Type: Feature Request
>          Components: Query Engine
>    Affects Versions: 7.7.2
>            Reporter: Johnathon Lee
>            Assignee: Steven Hawkins
>
> The issue here is this is an outer join and the inner side (the already sorted side) will be buffered regardless.  Current logic does not catch blocked exceptions from one side and pro-actively buffer the other - rather we are serially performing the sort and then continue with the loading of the inner side
> For inner joins there is a clear trade-off between execution speed and buffering so this behavior may have to be hint or config driven for non-dependent non-outer joins.

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