[teiid-issues] [JBoss JIRA] (TEIID-3743) Multiple Count Distinct Columns Fails for Impala

[Scott Wallace (JIRA)]

    [ https://issues.jboss.org/browse/TEIID-3743?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13242696#comment-13242696 ] 

Scott Wallace commented on TEIID-3743:
--------------------------------------

Error from Designer running a query with two count distincts:
{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 = 2149 GROUP BY g_0.process_date_key]
{noformat}


> Multiple Count Distinct Columns Fails for Impala
> ------------------------------------------------
>
>                 Key: TEIID-3743
>                 URL: https://issues.jboss.org/browse/TEIID-3743
>             Project: Teiid
>          Issue Type: Bug
>          Components: Misc. Connectors
>    Affects Versions: 8.11.4
>            Reporter: Scott Wallace
>            Assignee: Steven Hawkins
>             Fix For: 8.12
>
>
> Teiid Impala translator incorrectly allows multiple count distinct columns, which fails to execute since it is not supported by Impala.
> Per Cloudera documentation:
> {quote}By default, Impala only allows a single COUNT(DISTINCT columns) expression in each query.
> To produce the same result as multiple COUNT(DISTINCT) expressions, you can use the following technique for queries involving a single table:
> select v1.c1 result1, v2.c1 result2 from (select count(distinct col1) as c1 from t1) v1 cross join (select count(distinct col2) as c1 from t1) v2;{quote}
> The Teiid-Impala translator should ideally rewrite the query as necessary so that the query does not fail executing multiple count distincts against Impala.



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