[teiid-issues] [JBoss JIRA] Closed: (TEIID-1529) LIMIT not pushed down for queries with subselects and ORDER BY

[Steven Hawkins (JIRA)]

     [ https://issues.jboss.org/browse/TEIID-1529?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Steven Hawkins closed TEIID-1529.
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> LIMIT not pushed down for queries with subselects and ORDER BY
> --------------------------------------------------------------
>
>                 Key: TEIID-1529
>                 URL: https://issues.jboss.org/browse/TEIID-1529
>             Project: Teiid
>          Issue Type: Bug
>          Components: Query Engine
>    Affects Versions: 7.3
>            Reporter: Mark Addleman
>            Assignee: Steven Hawkins
>             Fix For: 7.4
>
>
> It doesn't look like the engine pushes down LIMIT in the following query:
> SELECT B."SYSID", B."USERID", (SELECT COUNT(*)  FROM 
> (SELECT * FROM notes.RETRIEVE_NOTES WHERE OBJECT_PKEY = XMLSERIALIZE(XMLELEMENT("SECURITY.BASEUSER", XMLATTRIBUTES(B."SYSID",B."USERID")) as String)) as foo) as C_notesForObject, 'SECURITY.BASEUSER' as "__objecttype__" FROM "SECURITY.BASEUSER" as B ORDER BY B."USERID" ASC LIMIT 10 
> However, the engine does push down the LIMIT in the same query without the ORDER BY:
> SELECT B."SYSID", B."USERID", (SELECT COUNT(*)  FROM 
> (SELECT * FROM notes.RETRIEVE_NOTES WHERE OBJECT_PKEY = XMLSERIALIZE(XMLELEMENT("SECURITY.BASEUSER", XMLATTRIBUTES(B."SYSID",B."USERID")) as String)) as foo) as C_notesForObject, 'SECURITY.BASEUSER' as "__objecttype__" FROM "SECURITY.BASEUSER" as B LIMIT 10 
> Another piece of relevant information is notes.RETRIEVE_NOTE is a stored procedure backed by java code in a translator.
> Since SECURITY.BASEER contains ~20,000 rows and each row requires a select against the RETRIEVE_NOTE stored procedure, the difference in processing time is huge:  about two minutes with the ORDER BY versus a few hundred milliseconds without the ORDER BY.

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