ARROW-12048: [Rust][DataFusion] Support Common Table Expressions #9776
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Dandandan
commented
Mar 23, 2021
…rence, add more tests
jorgecarleitao
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Mar 23, 2021
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jorgecarleitao
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LGTM. Thanks @Dandandan !
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Thank you for this @Dandandan ! I plan to review this carefully tomorrow |
returnString
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Mar 23, 2021
Dandandan
commented
Mar 24, 2021
| let logical_plan = self.query_to_plan_with_alias( | ||
| &cte.query, | ||
| Some(cte.alias.name.value.clone()), | ||
| &mut ctes.clone(), |
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This clone is now relatively inefficient for very long and/or deep ctes.
Solutions I see for this problem.
- use an immutable HashMap (O(1) clone, easier to program), example: https://docs.rs/im/15.0.0/im/struct.HashMap.html
- use something like "frames", e.g.
Vec<HashMap<String, LogicalPlan>>-> when looking up a reference first look up level 0, level-1, level -2, etc. - cleanup the variables before returning (removing / replacing the added references)
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I think the frames idea makes the most sense to me -- namely a stack
We can handle it in the future if/when it shows itself to be a problem
alamb
approved these changes
Mar 24, 2021
| let logical_plan = self.query_to_plan_with_alias( | ||
| &cte.query, | ||
| Some(cte.alias.name.value.clone()), | ||
| &mut ctes.clone(), |
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I think the frames idea makes the most sense to me -- namely a stack
We can handle it in the future if/when it shows itself to be a problem
alamb
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Mar 28, 2021
… of SQL features @Dandandan added the feature in #9776, updating docs to keep pace Closes #9795 from alamb/alamb/CTE Authored-by: Andrew Lamb <[email protected]> Signed-off-by: Andrew Lamb <[email protected]>
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This adds support for CTE syntax:
Before this PR, the CTE syntax was ignored.
This PR supports CTEs referening a previous CTE within the same query (but no forward references)