cchanyi opened a new issue #11910:
URL: https://github.com/apache/druid/issues/11910


   This is similar to https://github.com/apache/druid/issues/9914 and others 
related. The workaround does not work for Quantiles and HLL in 0.21.1.
   
   ### Affected Version
   
   0.21.1
   
   ### Description
   Using a very simple example in the console. The goal is to take a 
dimensional column from the source table and create a new datasource that 
aggregates that column into a Quantile sketch if it's a number or HLL Sketch if 
it's a string. I can sum the number column as a metric, but the Quantiles or 
HLL are empty.
   
   The workaround listed is actually populated now from the Load Data in 
console. The fix was to include the dimensions from the source datasource as 
metrics in the inputSource. If I have a dimension called `dim_double` - I can 
sum that dimension, but cannot quantiles from it. With the string dimension 
called `dim_string` - I cannot get HLL sketch from this.
   
   ```
    "ioConfig": {
         "type": "index_parallel",
         "inputSource": {
           "type": "druid",
           "dataSource": "source_datasource",
           "interval": "2021-08-18/2021-08-19",
           "metrics": [
             "count",
             "dim_double",
             "dim_string"
           ]
         },
         "appendToExisting": false
       },
   ```
   Then, the metricSpec looks like:
   
   ```
    "metricsSpec": [
           {
             "type": "longSum",
             "name": "count",
             "fieldName": "count",
             "expression": null
           },
           {
             "name": "hll_dim_string",
             "type": "HLLSketchBuild",
             "fieldName": "dim_string"
           },
           {
             "fieldName": "dim_double", 
             "type": "doubleSum", 
             "name": "sum_dim_double"
           }, 
           {
             "name": "quantiles_doubles_dim_double",
             "type": "quantilesDoublesSketch",
             "fieldName": "dim_double"
           }
         ],
   ```
   
   I have not tested on earlier versions. This seems like a common use-case. 
Note, if I build the spec from the source data it does work. 
   


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