[teiid-issues] [JBoss JIRA] (TEIID-2990) MongoDB: Usage of lookup() function throws an exception

[Ramesh Reddy (JIRA)]

     [ https://issues.jboss.org/browse/TEIID-2990?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Ramesh Reddy resolved TEIID-2990.
---------------------------------

        Labels: Beta1  (was: )
    Resolution: Done


Upon investigation it looks like <2.6 version of the MongoDB do not support scalar values in the $projection. In version 2.6 they introduced $literal construct with which it is possible.

So, added the version class from jdbc translator, but parked the default server version as 2.4 in the translator. If translator sees this situation in the query, then it will error with proper message, however if user is working with 2.6 version and have properly set the database version in the translator override properties to 2.6 then it will use the $literal construct and return correct result.

> MongoDB: Usage of lookup() function throws an exception
> -------------------------------------------------------
>
>                 Key: TEIID-2990
>                 URL: https://issues.jboss.org/browse/TEIID-2990
>             Project: Teiid
>          Issue Type: Bug
>          Components: Misc. Connectors
>    Affects Versions: 8.4.1
>            Reporter: Filip Elias
>            Assignee: Ramesh Reddy
>              Labels: Beta1
>             Fix For: 8.7.1, 8.8
>
>         Attachments: server.log
>
>
> Exception[1] is thrown when function lookup() is used in SQL query. 
> Mongo translator doesn't support selection of constants only, which causes the exception(select 1, select 'hi' from smalla).
> {code}
> [1]  3:59:20,997 ERROR [org.teiid.CONNECTOR] (Worker5_QueryProcessorQueue6) Connector worker process failed for atomic-request=Ef2Z7E0246by.1.5.3: com.mongodb.CommandFailureException: { "serverUsed" : "localhost/127.0.0.1:27017" , "errmsg" : "exception: $projection requires at least one output field" , "code" : 16403 , "ok" : 0.0}
> 	at com.mongodb.CommandResult.getException(CommandResult.java:71)
> {code}
> Server log is in the attachment.
> Sample query:
> {code}
> SELECT BQT1.SmallA.IntKey FROM BQT1.SmallA, BQT1.SmallB WHERE BQT1.SmallA.IntKey= lookup('BQT1.SmallB', 'IntKey', 'StringKey', BQT1.SmallA.StringKey) ORDER BY IntKey
> {code}
> Generated mongo commands:
> {code}
> { aggregate: "smalla", pipeline: [ { $project: { _m0: "$INTKEY", _m1: "$STRINGKEY" } } ] }
> {code}
> and 
> {code}
> { aggregate: "smallb", pipeline: [ { $project: {} } ] }
> {code}



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