[jira] [Closed] (CALCITE-1098) Set Mergence trigger relNode cyclical reference (ProjectMergeRule)

["Jane Lian (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/CALCITE-1098?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Jane Lian closed CALCITE-1098.
------------------------------
    Resolution: Not A Problem

> Set Mergence trigger relNode cyclical reference (ProjectMergeRule)
> ------------------------------------------------------------------
>
>                 Key: CALCITE-1098
>                 URL: https://issues.apache.org/jira/browse/CALCITE-1098
>             Project: Calcite
>          Issue Type: Bug
>            Reporter: Jane Lian
>            Assignee: Julian Hyde
>         Attachments: projectMergeTest.patch
>
>
> The issue is found in applying ProjectMergeRule. Following is the case which triggers the relNode's cyclical reference.
> For instance suppose you have following set tree:
> {code}
> Set#2: Project
>   rel#3:Subset#2.NONE
>      rel#4: (‘a’) with input (rel#5:Subset#1.NONE)
> Set#1: Project
>   rel#5:Subset#1.NONE
>      rel#6: (‘a’) with input (rel#7:Subset#0.NONE)
> Set#0: TableScan
>   rel#7:Subset#0.NONE
>      rel#8:Dept
> {code}
> Project#2- Project#1 triggers the ProjectMerge Rule, then a new equivalent Project will be generated, such as, 
> rel#9: (‘a’) with input (rel#7:Subset#0.NONE).
> When the planner is registering rel#9,  it will try to find the equivalent relNode which is reserved in mapDigestToRel. In the above case, rel#6 would be found. The set#2 and set#1 would be merged, then the following is the set tree after mergence:
> {code}
> Set#1: Project
>    rel#5:Subset#1.NONE
>      rel#4: (‘a’) with input (rel#5:Subset#1.NONE)
>      rel#6: (‘a’) with input (rel#7:Subset#0.NONE)
> Set#0: TableScan
>    rel#7:Subset#0.NONE
>      rel#8: Dept
> {code}
> rel#4's input is set#1, then there is a cyclical reference.



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