[teiid-issues] [JBoss JIRA] (TEIID-4227) Impala Translator - Support Multiple Count Distinct with Group By

[Steven Hawkins (JIRA)]

    [ https://issues.jboss.org/browse/TEIID-4227?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13243384#comment-13243384 ] 

Steven Hawkins commented on TEIID-4227:
---------------------------------------

> Hi Steven Hawkins an approximate count distinct isn't going to work for us as our reporting requires exact results.

That's unfortunate as that would greatly simply things.  Do you have an idea of the performance implications here?  That is there a threshold at which it's better for Teiid to perform the aggregation?  For example would it be possible to test with a patched or other translator modification that disables group by support?

> One solution could be to use NVL around the join column

That does not work as you can conflict with actual values.

> Impala Translator - Support Multiple Count Distinct with Group By
> -----------------------------------------------------------------
>
>                 Key: TEIID-4227
>                 URL: https://issues.jboss.org/browse/TEIID-4227
>             Project: Teiid
>          Issue Type: Feature Request
>          Components: Misc. Connectors
>    Affects Versions: 8.13.3
>            Reporter: Scott Wallace
>            Assignee: Steven Hawkins
>
> This is somewhat related to TEIID-3743, which added support of multiple count distinct metrics. We have a requirement to allow multiple count distinct metrics grouped by common attributes.
> Currently, we get a failure as follows:
> {noformat}org.teiid.runtime.client.TeiidClientException: java.lang.RuntimeException: Remote org.teiid.core.TeiidProcessingException: TEIID30504 vw_impression_click_transaction_process_date_detail: 500051 TEIID11008:TEIID11004 Error executing statement(s): [Prepared Values: [] SQL: SELECT g_0.process_date_key, SUM(g_0.num_clicks), SUM(g_0.num_impressions), COUNT(DISTINCT g_0.orderid), COUNT(DISTINCT g_0.`hash_tid`), SUM(g_0.sales) FROM detail.vw_impression_click_transaction_process_date_detail g_0 WHERE g_0.process_date_key >= '2016-05-22' AND g_0.process_date_key < '2016-05-23' AND g_0.advertiser_key = 12345 GROUP BY g_0.process_date_key]
> {noformat}
> To allow this request to succeed, we could have translator write that Impala query as:
> {noformat}
> select nvl(v1.c1,v2.c1), nvl(v1.c2,v1.c2), nvl(v1.c3,v1.c3), v1.c4, v2.c5, nvl(v1.c6,v1.c6)  from (
> SELECT g_0.process_date_key as c1,
>          SUM(g_0.num_clicks) as c2,
>          SUM(g_0.num_impressions) as c3,
>          COUNT(DISTINCT g_0.orderid) as c4,
>          SUM(g_0.sales) as c6
> FROM detail.vw_impression_click_transaction_process_date_detail g_0
> WHERE g_0.process_date_key >= '2016-05-22'
>         AND g_0.process_date_key < '2016-05-23'
>         AND g_0.advertiser_key = 12345
> GROUP BY  g_0.process_date_key
>   ) v1 inner join
>   (
>     SELECT g_0.process_date_key as c1,
>          SUM(g_0.num_clicks) as c2,
>          SUM(g_0.num_impressions) as c3,
>          COUNT(DISTINCT g_0.`hash_tid`) as c5,
>          SUM(g_0.sales) as c6
> FROM detail.vw_impression_click_transaction_process_date_detail g_0
> WHERE g_0.process_date_key >= '2016-05-22'
>         AND g_0.process_date_key < '2016-05-23'
>         AND g_0.advertiser_key = 12345
> GROUP BY  g_0.process_date_key
>    ) v2 on v1.c1 = v2.c1;
> {noformat}
> FYI [~shawkins]



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