[Bug] Relation#union fails on virtual columns #421
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- When merging relations with virtual columns the qualified projection (added in rom-rb#334) causes the virtual column to be moved into the outer select. This means that column will always be hardcoded to `NULL` instead of selecting from the result of the union. This is a [not-that-esoteric technique with unions](https://stackoverflow.com/a/39766372). This also worked in ROM prior to rom-rb#334. This PR is really an issue/bug report just in the form of a failing test. I don't have a good idea as to what the right solutin is but I figured it would be helpful to at least have a very concrete demonstration of the issue.
dgollahon
commented
Jun 3, 2023
| # SELECT | ||
| # `users__tasks`.`id`, | ||
| # `users__tasks`.`name`, | ||
| # NULL AS 'title' |
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this is the problematic column select. if this got transformed to users__tasks.title, all would be well
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NULLinstead of selecting from the result of the union. This is a not-that-esoteric technique with unions. This also worked in ROM prior to Properly qualify relations when in Relation#union #334.This PR is really an issue/bug report just in the form of a failing test. I don't have a good idea as to what the right solutin is but I figured it would be helpful to at least have a very concrete demonstration of the issue.