[
https://issues.apache.org/jira/browse/CALCITE-1578?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15827140#comment-15827140
]
Julian Hyde commented on CALCITE-1578:
--------------------------------------
Cancel that. In a {{groupBy}} query, {{limitSpec}} seems to operate over the
granularity rather than globally. That's not what we want.
So, best we can do is generate a {{groupBy}} query with {{granularity = all}}
and to the sort/limit outside.
[~jcamachorodriguez], Please review
https://github.com/julianhyde/calcite/tree/1578-druid-aggregate-sort-limit,
which has a fix for this and CALCITE-1579.
[~gian], Let me know if you can think of a way we could be generating more
efficient queries (either {{topN}}, or {{groupBy}} with a {{limitSpec}}) for
SQL queries that have {{GROUP BY ... LIMIT}}.
> Druid adapter: wrong semantics of topN query limit with granularity
> -------------------------------------------------------------------
>
> Key: CALCITE-1578
> URL: https://issues.apache.org/jira/browse/CALCITE-1578
> Project: Calcite
> Issue Type: Bug
> Components: druid
> Affects Versions: 1.11.0
> Reporter: Jesus Camacho Rodriguez
> Assignee: Jesus Camacho Rodriguez
> Priority: Critical
>
> Semantics of Druid topN query with limit and granularity is not equivalent to
> input SQL. In particular, limit is applied on each granularity value, not on
> the overall query.
> Currently, the following query will be transformed into a topN query:
> {code:sql}
> SELECT i_brand_id, floor_day(`__time`), max(ss_quantity),
> sum(ss_wholesale_cost) as s
> FROM store_sales_sold_time_subset
> GROUP BY i_brand_id, floor_day(`__time`)
> ORDER BY s DESC
> LIMIT 10;
> {code}
> Previous query outputs at most 10 rows. In turn, the equivalent SQL query for
> a Druid topN query should be expressed as:
> {code:sql}
> SELECT rs.i_brand_id, rs.d, rs.m, rs.s
> FROM (
> SELECT i_brand_id, floor_day(`__time`) as d, max(ss_quantity) as m,
> sum(ss_wholesale_cost) as s,
> ROW_NUMBER() OVER (PARTITION BY floor_day(`__time`) ORDER BY
> sum(ss_wholesale_cost) DESC ) AS rownum
> FROM store_sales_sold_time_subset
> GROUP BY i_brand_id, floor_day(`__time`)
> ) rs
> WHERE rownum <= 10;
> {code}
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
