[teiid-issues] [JBoss JIRA] (TEIID-5682) Raise aggregation to allow for join pushdown

[Steven Hawkins (Jira)]

    [ https://issues.jboss.org/browse/TEIID-5682?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13713478#comment-13713478 ] 

Steven Hawkins commented on TEIID-5682:
---------------------------------------

With cardinalities set this issue is somewhat mitigated as the join will be planned as a dependent join.  The rationale for raising the aggregation is if the cardinalties aren't set and the join can be pushed.  The grouping and order by operations can then be combined.

> Raise aggregation to allow for join pushdown
> --------------------------------------------
>
>                 Key: TEIID-5682
>                 URL: https://issues.jboss.org/browse/TEIID-5682
>             Project: Teiid
>          Issue Type: Enhancement
>          Components: Query Engine
>            Reporter: Steven Hawkins
>            Assignee: Steven Hawkins
>            Priority: Major
>             Fix For: 12.2
>
>
> In some plans, for example those created by odata expand see TEIID-5680, the resulting query has the form of:
> select tbl1-cols from tbl1 left outer join (select cols, aggregates ... from tbl2 group by cols) on (some non-aggregate predicate)
> If the aggregates or other intervening constructs are not able to be pushed the result will be a federated join.
> In most instances (where the tbl1 columns are sortable) it's possible to change this to:
> select tbl1-cols aggregates from tbl1 left outer join tbl1 on (...)  group by tbl1-cols, cols
> which can allow the pushdown of the join to proceed.



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