[jira] [Commented] (CALCITE-1588) Add SQL syntax to allow approximate LIMIT and distinct-COUNT

["Ethan Wang (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-1588?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16106858#comment-16106858 ] 

Ethan Wang commented on CALCITE-1588:
-------------------------------------

regarding syntax {code}COUNT(DISTINCT customerId) APPROXIMATE (WITHIN 10 PERCENT)){code}

Seems to me Druid implemented the approx distinct count using HyperLogLog. In HyperLogLog, I don't think it's common for user to specify the accuracy, since the accuracy is implied in the algorithm and only related to a constant. So the goal is always "as most accurate as possible". Is that true in Druid? [~gian]

> Add SQL syntax to allow approximate LIMIT and distinct-COUNT
> ------------------------------------------------------------
>
>                 Key: CALCITE-1588
>                 URL: https://issues.apache.org/jira/browse/CALCITE-1588
>             Project: Calcite
>          Issue Type: Bug
>            Reporter: Julian Hyde
>            Assignee: Julian Hyde
>
> Add SQL syntax to allow approximate LIMIT and distinct-COUNT. These will set the properties specified in CALCITE-1587. By default the properties are false, so the query will return exact results.
> Exact syntax is to be decided. It could be at the top of the query (therefore affecting every LIMIT or aggregate in the query) or it could be more localized (e.g. {{COUNT(DISTINCT customerId) APPROXIMATE (WITHIN 10 PERCENT)}}).



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