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https://issues.apache.org/jira/browse/CALCITE-1787?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16032992#comment-16032992
]
slim bouguerra commented on CALCITE-1787:
-----------------------------------------
For instance if you want to query for how many unique users visited both
product A and B? the query to druid should look like
{code}
{
"queryType": "groupBy",
"dataSource": "test_datasource",
"granularity": "ALL",
"dimensions": [],
"filter": {
"type": "or",
"fields": [
{"type": "selector", "dimension": "product", "value": "A"},
{"type": "selector", "dimension": "product", "value": "B"}
]
},
"aggregations": [
{
"type" : "filtered",
"filter" : {
"type" : "selector",
"dimension" : "product",
"value" : "A"
},
"aggregator" : {
"type": "thetaSketch", "name": "A_unique_users", "fieldName":
"user_id_sketch"
}
},
{
"type" : "filtered",
"filter" : {
"type" : "selector",
"dimension" : "product",
"value" : "B"
},
"aggregator" : {
"type": "thetaSketch", "name": "B_unique_users", "fieldName":
"user_id_sketch"
}
}
],
"postAggregations": [
{
"type": "thetaSketchEstimate",
"name": "final_unique_users",
"field":
{
"type": "thetaSketchSetOp",
"name": "final_unique_users_sketch",
"func": "INTERSECT",
"fields": [
{
"type": "fieldAccess",
"fieldName": "A_unique_users"
},
{
"type": "fieldAccess",
"fieldName": "B_unique_users"
}
]
}
}
],
"intervals": [
"2014-10-19T00:00:00.000Z/2014-10-22T00:00:00.000Z"
]
}
{code}
> 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: Zain Humayun
> 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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