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https://issues.apache.org/jira/browse/CALCITE-5928?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17754214#comment-17754214
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Julian Hyde commented on CALCITE-5928:
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Thanks for logging this case. Complex cases may be difficult to solve with
transformation rules because the goal (the interesting order required by, say,
a join) may be several relational operators above the source of the ordering.
But let's see how far we can go with stepwise transformation rules.
> Add SortHomogenizeRule for homogenization sort fields for futher optimize
> -------------------------------------------------------------------------
>
> Key: CALCITE-5928
> URL: https://issues.apache.org/jira/browse/CALCITE-5928
> Project: Calcite
> Issue Type: New Feature
> Reporter: JingDas
> Assignee: JingDas
> Priority: Minor
>
> When an interesting order is pushed down, some columns may have to be
> substituted with equivalent columns in the new context. This is referred to
> as homogenuzatzon.
> For example, consider the following query:
>
> {code:java}
> select * from sales.emp e
> left join (
> select * from sales.dept d) d on e.deptno = d.deptno
> order by e.sal, d.deptno{code}
> The filed `e.sal`, `d.deptno` will not push down through join, because
> d.deptno is unavalilable until after the join.
>
> We can homogenize the sort fields from `e.sal`, `d.deptno` to `e.sal`,
> `e.deptno` since
> e.deptno = d.deptno. Then sort fields can be pushed down by
> `SortJoinTransposeRule`
> The theoretical basis comes from paper [Fundamental Techniques for Order
> Optimization|https://dl.acm.org/doi/pdf/10.1145/233269.233320]
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