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https://issues.apache.org/jira/browse/CALCITE-1742?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15965015#comment-15965015
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Jinfeng Ni commented on CALCITE-1742:
-------------------------------------

[~maryannxue], it makes sense to remove the side effect of two places you 
identified, by removing {{schema.add()}} function call.  

Make sense to me that {{Schema}} should always return same {{Table}} object for 
the same table, regardless of single statement or multiple statement. The same 
{{Table}} instance could be wrapped in different RelOptTableImpl objects.  

I have one question. Will it cause problem if  {CsvSchema} only initializes 
"tableMap" just once? What if the files in one the directory have been added / 
deleted between multiple statement execution?

 




> CalciteCatalogReader should not add resolved tables into CalciteSchema's 
> explicit table map
> -------------------------------------------------------------------------------------------
>
>                 Key: CALCITE-1742
>                 URL: https://issues.apache.org/jira/browse/CALCITE-1742
>             Project: Calcite
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 1.12.0
>            Reporter: Maryann Xue
>            Assignee: Maryann Xue
>
> {{CalciteSchema}} is designed to have two sets of objects, the explicit and 
> the implicit. A explicit object means an object we add through explicit 
> {{CalciteSchema#addTable}} (or {{CalciteSchema.addFunction}}, etc) calls, 
> while an implicit object means an object we get from the underlying 
> {{Schema}} object's getXXX methods.
>  
> However, in {{CalciteCatalogReader#getTableFrom}}, after a table is resolved 
> through {{CalciteSchema.getTable}} method, it will be added to the 
> {{CalciteSchema}} again as an explicit object regardless of whether it is 
> originally implicit or explicit. So if it happens to be an implicit table, 
> any change about that table later on will be shadowed by the newly added 
> explicit object and thus cannot be accessed.



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