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

[Scott Wallace (JIRA)]

    [ https://issues.jboss.org/browse/TEIID-4227?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13243367#comment-13243367 ] 

Scott Wallace commented on TEIID-4227:
--------------------------------------

Hi [~shawkins] an approximate count distinct isn't going to work for us as our reporting requires exact results.

I see what you mean about nulls in the on clause, though.

One solution could be to use NVL around the join column. However, you'd need to be aware of data types.

if c1 is a string you could use: nvl(v1.c1,'') = nvl(v2.c1,'')
if c1 is a number you could use: nvl(v1.c1,0) = nvl(v2.c1,0)

You still get the correct null value in the results, but the join is handled.

> 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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