[teiid-issues] [JBoss JIRA] (TEIID-2902) More incremental join when a limit is present

[Steven Hawkins (JIRA)]

    [ https://issues.jboss.org/browse/TEIID-2902?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12965224#comment-12965224 ] 

Steven Hawkins commented on TEIID-2902:
---------------------------------------

My first thought was to use the SortUtility singlePassSort logic and merge in subsets, but that will require additional work as even the single pass currently reads all results prior to returning the sorted sublists.  We need it to be iterative in this scenario.

> More incremental join when a limit is present
> ---------------------------------------------
>
>                 Key: TEIID-2902
>                 URL: https://issues.jboss.org/browse/TEIID-2902
>             Project: Teiid
>          Issue Type: Enhancement
>          Components: Query Engine
>    Affects Versions: 8.7
>            Reporter: Ivan Chan
>            Assignee: Steven Hawkins
>             Fix For: 8.8
>
>
> For SQL like:
> SELECT 
>      t1.column1, 
>      t2.column1
> FROM 
>      schema1.table1 t1, 
>      schema2.table1 t2
> WHERE 
>      t1.column2=t2.column2
> LIMIT 100
> Teiid may get the whole schema1.table1 content and the whole schema2.table1 content, do the join in memory and then, limit the resultset to 100 records.
> However, I think teiid can fetch smaller set of data then do a join.  If the join result set is less than number of rows asking,  keep fetching next set of data and do a join until hits the limit number.



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