You are viewing a plain text version of this content. The canonical link for it is here.
Posted to commits@druid.apache.org by GitBox <gi...@apache.org> on 2022/09/20 22:41:59 UTC
[GitHub] [druid] techdocsmith commented on a diff in pull request #13128: Clarified the behaviour of SQL COUNT(DISTINCT dim) on multi-value dimensions
techdocsmith commented on code in PR #13128:
URL: https://github.com/apache/druid/pull/13128#discussion_r975870723
##########
docs/querying/sql-aggregations.md:
##########
@@ -66,7 +66,7 @@ In the aggregation functions supported by Druid, only `COUNT`, `ARRAY_AGG`, and
|Function|Notes|Default|
|--------|-----|-------|
|`COUNT(*)`|Counts the number of rows.|`0`|
-|`COUNT(DISTINCT expr)`|Counts distinct values of `expr`.<br /><br />When `useApproximateCountDistinct` is set to "true" (the default), this is an alias for `APPROX_COUNT_DISTINCT`. The specific algorithm depends on the value of [`druid.sql.approxCountDistinct.function`](../configuration/index.md#sql). In this mode, you can use strings, numbers, or prebuilt sketches. If counting prebuilt sketches, the prebuilt sketch type must match the selected algorithm.<br /><br />When `useApproximateCountDistinct` is set to "false", the computation will be exact. In this case, `expr` must be string or numeric, since exact counts are not possible using prebuilt sketches. In exact mode, only one distinct count per query is permitted unless `useGroupingSetForExactDistinct` is enabled.|`0`|
+|`COUNT(DISTINCT expr)`|Counts distinct values of `expr`.<br /><br />When `useApproximateCountDistinct` is set to "true" (the default), this is an alias for `APPROX_COUNT_DISTINCT`. The specific algorithm depends on the value of [`druid.sql.approxCountDistinct.function`](../configuration/index.md#sql). In this mode, you can use strings, numbers, or prebuilt sketches. If counting prebuilt sketches, the prebuilt sketch type must match the selected algorithm.<br /><br />When `useApproximateCountDistinct` is set to "false", the computation will be exact. In this case, `expr` must be string or numeric, since exact counts are not possible using prebuilt sketches. In exact mode, only one distinct count per query is permitted unless `useGroupingSetForExactDistinct` is enabled.<br /><br />Will count each distinct value in a [`multi-value`](../querying/multi-value-dimensions.md)-row seperately.|`0`|
Review Comment:
```suggestion
|`COUNT(DISTINCT expr)`|Counts distinct values of `expr`.<br /><br />When `useApproximateCountDistinct` is set to "true" (the default), this is an alias for `APPROX_COUNT_DISTINCT`. The specific algorithm depends on the value of [`druid.sql.approxCountDistinct.function`](../configuration/index.md#sql). In this mode, you can use strings, numbers, or prebuilt sketches. If counting prebuilt sketches, the prebuilt sketch type must match the selected algorithm.<br /><br />When `useApproximateCountDistinct` is set to "false", the computation will be exact. In this case, `expr` must be string or numeric, since exact counts are not possible using prebuilt sketches. In exact mode, only one distinct count per query is permitted unless `useGroupingSetForExactDistinct` is enabled.<br /><br />Counts each distinct value in a [`multi-value`](../querying/multi-value-dimensions.md)-row separately.|`0`|
```
Thanks for contributing, @hosswald ! My suggestion fixes a typo + avoids future tense
--
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.
To unsubscribe, e-mail: commits-unsubscribe@druid.apache.org
For queries about this service, please contact Infrastructure at:
users@infra.apache.org
---------------------------------------------------------------------
To unsubscribe, e-mail: commits-unsubscribe@druid.apache.org
For additional commands, e-mail: commits-help@druid.apache.org