[GitHub] [incubator-druid] pdeva opened a new issue #7584: Cant refer to variables declared inside sql statements for post aggregations

[GitBox <gi...@apache.org>]

pdeva opened a new issue #7584: Cant refer to variables declared inside sql statements for post aggregations
URL: https://github.com/apache/incubator-druid/issues/7584
 
 
   
   ### Affected Version
   
   0.14.0-iap4
   
   ### Description
   
   I am trying to use fields declared using `AS` to perform postaggregations.
   In this example I declare `memTotal` and `memUsed` and try to use it to calculate `pct`
   
   However this *does not* work:
   
   ```sql
   
   SELECT "cluster", sum ("mem_limit") as memTotal, sum ("mem_used") as memUsed,  
   (memUsed*100.0/memTotal)  as pct  /*this causes problems*/
   FROM "metrics"
   WHERE   "__time" >= TIMESTAMP '2019-04-30 20:17:46' AND "__time" < TIMESTAMP '2019-04-30 20:17:48'   
   group by "cluster"
   ```
   
   resulting in exception:
   ```
   Bad Request: Unknown exception: org.apache.calcite.runtime.CalciteContextException: From line xxx: Column 'memUsed' not found in any table
   ```
   
   Instead I need to repeat the `sum ("mem_used")` everywhere...
   
   So this works, but i with redundant code for `memTotal` and `memUsed` for `pct`
   ```sql
   
   SELECT "cluster", sum ("mem_limit") as memTotal, sum ("mem_used") as memUsed,  
   (sum ("mem_used")*100.0/sum ("mem_limit"))  as pct /*need to repeat sum calculation here*/
   FROM "metrics"
   WHERE   "__time" >= TIMESTAMP '2019-04-30 20:17:46' AND "__time" < TIMESTAMP '2019-04-30 20:17:48'   
   group by "cluster"
   ```

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