[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:all-tabpanel ]

Steven Hawkins resolved TEIID-2902.
-----------------------------------

    Resolution: Done


In most circumstances where a sort is not pushed we'll elect to do an EnhancedSortMerge join.  This change removes several places that forced us to fully read both sides.  It also in the presence of a limit ensure that a more incremental join is performed (one side fully sorted, the other will only be sorted to a single pass  - but will typically have been fully read).

> 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.



--
This message was sent by Atlassian JIRA
(v6.2.3#6260)