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https://issues.apache.org/jira/browse/CALCITE-5309?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17714252#comment-17714252
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Julian Hyde commented on CALCITE-5309:
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Many thanks for doing this research. I agree with everything except that Cursor
should be a new type of relational expression. I think cursor is just a *use*
of a relational expression, so any existing relational expression will do.
I expect there will need to be a method something like 'RelNode
implementCursor(int)'.
(Why is the cursor concept needed in the SQL syntax and the AST but not needed
in the relational algebra? I'm not totally sure, but I think it has something
to do with namespaces. Relational algebra doesn't need namespaces, because each
relational expression just refers to its inputs. The {{Spool}} operator - see
CALCITE-481 - deals with the outlier case that referring to an input is not
sufficient.)
> Accept cursors as inputs of table functions
> -------------------------------------------
>
> Key: CALCITE-5309
> URL: https://issues.apache.org/jira/browse/CALCITE-5309
> Project: Calcite
> Issue Type: New Feature
> Reporter: Bertil Chapuis
> Assignee: Bertil Chapuis
> Priority: Major
>
> The TableFunctionTest.testTableFunctionCursorsInputs is currently disabled
> and a note says that it could not be implemented. This feature is necessary
> to implement table functions that take a query or a table as an input.
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