[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=12965643#comment-12965643 ] 

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

Not making much head way here as all of the sorting logic / join logic is fairly entangled and generally expects to read all values as part of the sorting operation (for example if any prefetch is performed, we'll read everything even before performing a single pass sort).

It looks like it would be easier to start over somewhat to avoid attempting to retro-fit too much.

> 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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