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Filtering on mutate() columns in Greenplum #484

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patrick-nicholson opened this issue Jul 7, 2014 · 3 comments
Closed

Filtering on mutate() columns in Greenplum #484

patrick-nicholson opened this issue Jul 7, 2014 · 3 comments
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@patrick-nicholson
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@patrick-nicholson patrick-nicholson commented Jul 7, 2014

Using filter on a column created by mutate (in this case rnk) fails with the error

> dp %>% mutate(rnk = min_rank(desc(salary))) %>% filter(rnk == 1)
Error in postgresqlExecStatement(conn, statement, ...) : 
  RS-DBI driver: (could not Retrieve the result : ERROR:  column "rnk" does not exist
LINE 3: WHERE "rnk" = 1.0) AS master
              ^
)

However, selecting the column rnk works:

> dp %>% mutate(rnk = min_rank(desc(salary))) %>% select(rnk)
   rnk
1    1
2    2
3    3
...

Due to the setup of R and Greenplum I have to use, I can't provide a replicable example. I'm not sure if this is a psql issue or specific to Greenplum. I don't get errors using local dataframes or sqlite.

@hadley
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@hadley hadley commented Jul 8, 2014

Could you please me the generated SQL? (Call the object x and then use x$sql

@patrick-nicholson
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@patrick-nicholson patrick-nicholson commented Jul 8, 2014

SELECT "first_name", "last_name", "emp_id", "hire_date", "salary", "dept",
       "exempt", "interests", rank() OVER (ORDER BY "salary" DESC) AS "rnk"
FROM "emp"
WHERE "rnk" = 1.0

@hadley
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@hadley hadley commented Jul 8, 2014

Oh hmm, I didn't think about using window functions when the data isn't grouped. It needs an intermediate subquery.

@hadley hadley added this to the 0.3 milestone Aug 1, 2014
@hadley hadley self-assigned this Aug 1, 2014
@hadley hadley closed this in 3ad8f46 Aug 28, 2014
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