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https://issues.apache.org/jira/browse/CALCITE-1787?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16023400#comment-16023400
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Zain Humayun commented on CALCITE-1787:
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[~bslim] that seems reasonable. So i've taken the liberty to test two queries,
which should have the same semantics:
1) {{select count(distinct "user_unique") from "foodmart" where "store_sales"
>= 0 and "store_cost" >= 0;}}
and
2) {{select count(distinct "user_unique") from "foodmart";}}
Both produce the same value, 5581. However, for #1 the plan looks something
like:
{quote}
BindableAggregate(group=\[{}\], EXPR$0=\[COUNT($0)\])
BindableAggregate(group=\[\{2\}\])
BindableFilter(condition=\[AND(>=($0, 0), >=($1, 0))\])
DruidQuery(table=\[\[foodmart, foodmart\]\], intervals=\[...\],
projects=\[\[$90, $91, $92\]\])
{quote}
I noticed calcite doesn't push the where clause into the Druid query (in the
"filter" field). Is this a missing feature/rule or am I misunderstanding
something?
> thetaSketch Support for Druid Adapter
> -------------------------------------
>
> Key: CALCITE-1787
> URL: https://issues.apache.org/jira/browse/CALCITE-1787
> Project: Calcite
> Issue Type: New Feature
> Components: druid
> Affects Versions: 1.12.0
> Reporter: Zain Humayun
> Assignee: Julian Hyde
> Priority: Minor
>
> Currently, the Druid adapter does not support the
> [thetaSketch|http://druid.io/docs/latest/development/extensions-core/datasketches-aggregators.html]
> aggregate type, which is used to measure the cardinality of a column
> quickly. Many Druid instances support theta sketches, so I think it would be
> a nice feature to have.
> I've been looking at the Druid adapter, and propose we add a new DruidType
> called {{thetaSketch}} and then add logic in the {{getJsonAggregation}}
> method in class {{DruidQuery}} to generate the {{thetaSketch}} aggregate.
> This will require accessing information about the columns (what data type
> they are) so that the thetaSketch aggregate is only produced if the column's
> type is {{thetaSketch}}.
> Also, I've noticed that a {{hyperUnique}} DruidType is currently defined, but
> a {{hyperUnique}} aggregate is never produced. Since both are approximate
> aggregators, I could also couple in the logic for {{hyperUnique}}.
> I'd love to hear your thoughts on my approach, and any suggestions you have
> for this feature.
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