jihoonson opened a new pull request #11083:
URL: https://github.com/apache/druid/pull/11083
### Description
Currently, `CAST` is ignored in the query plan when you use certain
aggregators on string columns after case. Taking a query, `SELECT
APPROX_QUANTILE_DS(CAST(dim1 as DOUBLE), 0.01) FROM foo`, as a example, Druid
creates a query plan like below.
```json
{
"queryType" : "timeseries",
"dataSource" : {
"type" : "table",
"name" : "foo"
},
"intervals" : {
"type" : "intervals",
"intervals" : [
"-146136543-09-08T08:23:32.096Z/146140482-04-24T15:36:27.903Z" ]
},
"descending" : false,
"virtualColumns" : [ ],
"granularity" : {
"type" : "all"
},
"aggregations" : [ {
"type" : "DoublesSketchAggregatorFactory",
"name" : "a0:agg",
"fieldName" : "dim1",
"k" : 128
} ],
"postAggregations" : [ {
"type" : "DoublesSketchToQuantilePostAggregator",
"name" : "a0",
"field" : {
"type" : "fieldAccess",
"name" : "a0:agg",
"fieldName" : "a0:agg"
},
"fraction" : 0.009999999776482582
} ]
}
```
As a result, this query always returns `0.0` because strings cannot be
casted to numbers implicitly. This PR fixes this issue by keeping `CAST` when
it casts from string to a number.
This PR additionally fixes NPE in `ApproximateHistogramBufferAggregator`
when the input column has nulls. Finally, some sqlAggregator tests are
refactored to use help functions in `BaseCalciteQueryTest`.
<hr>
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is met.
- [ ] added integration tests.
- [ ] been tested in a test Druid cluster.
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