[jira] [Resolved] (CALCITE-3865) RelCollationTraitDef.canConvert should always return true

["Haisheng Yuan (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CALCITE-3865?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Haisheng Yuan resolved CALCITE-3865.
------------------------------------
    Fix Version/s: 1.23.0
       Resolution: Fixed

Fixed in https://github.com/apache/calcite/commit/e7095a23cf6e082077c887588216df3e3862c20d.

> RelCollationTraitDef.canConvert should always return true
> ---------------------------------------------------------
>
>                 Key: CALCITE-3865
>                 URL: https://issues.apache.org/jira/browse/CALCITE-3865
>             Project: Calcite
>          Issue Type: Improvement
>          Components: core
>            Reporter: Haisheng Yuan
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 1.23.0
>
>         Attachments: image-2020-03-19-16-44-25-621.png, image-2020-03-19-16-47-21-805.png
>
>          Time Spent: 1h 40m
>  Remaining Estimate: 0h
>
> CALCITE-1148 introduced the following change to RelCollationTraitDef to fix RelTrait conversion bug, but it is just hiding the underlying issue and adding redundant and unnecessary check to planner.
> {code:java}
> @Override public boolean canConvert(RelOptPlanner planner,
>       RelCollation fromTrait, RelCollation toTrait, RelNode fromRel) {
>     // Returns true only if we can convert.  In this case, we can only convert
>     // if the fromTrait (the input) has fields that the toTrait wants to sort.
>     for (RelFieldCollation field : toTrait.getFieldCollations()) {
>       int index = field.getFieldIndex();
>       if (index >= fromRel.getRowType().getFieldCount()) {
>         return false;
>       }
>     }
>     return true;
>   }
> {code}
> The root cause is that logical operators, especially LogicalSort can have traits, which is a bad design decision, and {{AggregateReduceFunctionsRule}} and {{RelBuilder}} fails to adjust the column mapping in RelTraitSet. The newly created {{LogicalProject}} has collation on column 5 (it just copy its input's RelTraitSet blindly), but it only has 2 columns.
>  !image-2020-03-19-16-44-25-621.png! 



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