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Junxian Wu commented on CALCITE-1803: ------------------------------------- I updated the ticket with a new pull request in public github repo. Description and detailed solution can be viewed from the [PR](https://github.com/apache/calcite/pull/471). Please let me know anything on your guys mind. > Push Project that follows Aggregate down to Druid > ------------------------------------------------- > > Key: CALCITE-1803 > URL: https://issues.apache.org/jira/browse/CALCITE-1803 > Project: Calcite > Issue Type: New Feature > Components: druid > Affects Versions: 1.11.0 > Reporter: Junxian Wu > Assignee: Julian Hyde > Original Estimate: 336h > Remaining Estimate: 336h > > Druid post aggregations are not supported when parsing SQL queries. By > implementing post aggregations, we can offload some computation to the druid > cluster rather than aggregate on the client side. > Example usage: > {{SELECT SUM("column1") - SUM("column2") FROM "table";}} > This query will be parsed into two separate Druid aggregations according to > current rules. Then the results will be subtracted in Calcite. By using the > {{postAggregations}} field in the druid query, the subtraction could be done > in Druid cluster. Although the previous example is simple, the difference > will be obvious when the number of result rows are large. (Multiple rows > result will happen when group by is used). > Questions: > After I push Post aggregation into Druid query, what should I change on the > project relational correlation? In the case of the example above, the > {{BindableProject}} will have the expression to representation the > subtraction. If I push the post aggregation into druid query, the expression > of subtraction should be replaced by the representation of the post > aggregations result. For now, the project expression seems can only point to > the aggregations results. Since post aggregations have to point to > aggregations results too, it could not be placed in the parallel level as > aggregation. Where should I put post aggregations? -- This message was sent by Atlassian JIRA (v6.4.14#64029)