[teiid-issues] [JBoss JIRA] (TEIID-2983) MongoDB: Function "count()" returns sum instead of number of rows

[Ramesh Reddy (JIRA)]

    [ https://issues.jboss.org/browse/TEIID-2983?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12973871#comment-12973871 ] 

Ramesh Reddy commented on TEIID-2983:
-------------------------------------

I do not know if that type of sum statement can be build, mongodb processing is a pipeline. In order for SUM function to return the number documents (instead of summation) you would need to give it an "_id" based grouping, before the summation task and there can be only one "_id" in the pipeline execution.  So, now

{code}
select  count(*), count(CustomerId) from customer
{code}

will fail saying that multiple count aggregates are not allowed

however, queries like these are allowed
{code}
select  count(*), min(CustomerId) from customer
{code}

as these do not need the grouping construct.

> MongoDB: Function "count()" returns sum instead of number of rows
> -----------------------------------------------------------------
>
>                 Key: TEIID-2983
>                 URL: https://issues.jboss.org/browse/TEIID-2983
>             Project: Teiid
>          Issue Type: Bug
>          Components: Misc. Connectors
>    Affects Versions: 8.7.1
>            Reporter: Van Halbert
>            Assignee: Ramesh Reddy
>              Labels: Beta1
>             Fix For: 8.7.1, 8.8
>
>
> Function "count()" returns sum of rows instead of number of rows
> Query [1] returns sum of values of all rows of IntKey column.
> Query [2] correctly returns number of rows
>  
> [1] SELECT COUNT(IntKey) FROM BQT1.SmallA 
> [2] SELECT COUNT(*) FROM BQT1.SmallA



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