sthetland commented on a change in pull request #11883:
URL: https://github.com/apache/druid/pull/11883#discussion_r750528632
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File path: docs/querying/dimensionspecs.md
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@@ -65,32 +65,35 @@ Returns dimension values transformed using the given
[extraction function](#extr
}
```
-`outputType` may also be specified in an ExtractionDimensionSpec to apply type
conversion to results before merging. If left unspecified, the `outputType`
defaults to STRING.
+`outputType` may also be specified in an `ExtractionDimensionSpec` to apply
type conversion to results before merging. If left unspecified, the
`outputType` defaults to STRING.
Please refer to the [Output Types](#output-types) section for more details.
### Filtered DimensionSpecs
-These are only useful for multi-value dimensions. If you have a row in Apache
Druid that has a multi-value dimension with values ["v1", "v2", "v3"] and you
send a groupBy/topN query grouping by that dimension with [query
filter](filters.md) for value "v1". In the response you will get 3 rows
containing "v1", "v2" and "v3". This behavior might be unintuitive for some use
cases.
+A filtered `DimensionSpec` is only useful for multi-value dimensions. Say you
have a row in Apache Druid that has a multi-value dimension with values ["v1",
"v2", "v3"] and you send a groupBy/topN query grouping by that dimension with a
[query filter](filters.md) for a value of "v1". In the response you will get 3
rows containing "v1", "v2" and "v3". This behavior might be unintuitive for
some use cases.
+
+This happens because "query filter" is internally used on the bitmaps and only
used to match the row to be included in the query result processing. With
multi-value dimensions, "query filter" behaves like a contains check, which
will match the row with dimension value ["v1", "v2", "v3"].
Review comment:
I think the final clause is non-defining, so it should still be ", which
matches ..." The first sentence is confusing but I think it could accurately
say, "This happens because Druid uses the "query filter" internally on bitmaps
only to match the row...." Will edit separately
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