[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:all-tabpanel ]

Steven Hawkins resolved TEIID-2363.
-----------------------------------

    Fix Version/s: 8.3
       Resolution: Done


Modified the join logic to ensure that both sides of the join are processed as fully as possible in the presence of blocked exceptions.

In the exact case raised by this issue the ALREADY_SORTED side will default to a 10 batch prefetch (which will likely be buffered to disk).  The org.teiid.joinPrefetchBatches system property was added and doc'ed in the Admin Guide to increase that batch limit - which is appropriate for large joins where one side is being sorted and the other ALREADY_SORTED side is  relatively slow.
                
> 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
>             Fix For: 8.3
>
>
> 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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