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https://issues.apache.org/jira/browse/HIVE-287?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12884134#action_12884134
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John Sichi commented on HIVE-287:
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Yes, if you can do get it to work in the grammar itself (via a choice in the
existing "function" rule), that would be best. If it it's not possible to do
it there for some reason, then semantic analyzer.
Could you explain what you mean regarding impact? Since Hive doesn't support
COUNT(*) before your patch, the only impact is on the rest of your patch, right?
BTW, here's the relevant BNF from my copy of the SQL:2003 standard (ISO/IEC
9075-2:2003 part 2 section 10.9), omitting some SQL/OLAP stuff such as <filter
clause>:
<aggregate function > ::=
COUNT <left paren> <asterisk> <right paren>
| <general set function>
<general set function> ::=
<set function type> <left paren> [ <set quantifier> ] <value expression> <right
paren>
<set function type> ::=
AVG |
MAX |
MIN |
SUM |
...
<set quantifier> ::= DISTINCT | ALL
As you can see, they make a special case for COUNT to allow for star there
alone, and they don't allow COUNT(DISTINCT *).
> count distinct on multiple columns does not work
> ------------------------------------------------
>
> Key: HIVE-287
> URL: https://issues.apache.org/jira/browse/HIVE-287
> Project: Hadoop Hive
> Issue Type: Bug
> Components: Query Processor
> Reporter: Namit Jain
> Assignee: Arvind Prabhakar
> Attachments: HIVE-287-1.patch, HIVE-287-2.patch, HIVE-287-3.patch,
> HIVE-287-4.patch
>
>
> The following query does not work:
> select count(distinct col1, col2) from Tbl
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