Fix expression cloning when table changes in SelectExpression.VisitChildren#32456
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roji merged 1 commit intodotnet:mainfrom Dec 3, 2023
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Fix expression cloning when table changes in SelectExpression.VisitChildren#32456roji merged 1 commit intodotnet:mainfrom
roji merged 1 commit intodotnet:mainfrom
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maumar
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…ildren (dotnet#32456) Fixes dotnet#32234 (cherry picked from commit cf5ec40)
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When a table is changed in SelectExpression.VisitChildren() (on an immutable SelectExpression), visit the entire SelectExpression and replace ColumnExpressions to have them properly point to the new SelectExpression, without sharing TableReferenceExpression. This allows us to mutate the TableReferenceExpression later (i.e. alias uniquification) without affecting two queries in the tree.
There's a bit of added complexity here to prevent infinite recursion where the new ColumnTableReferenceUpdater that we call also uses SelectExpression.VisitChildren, but we don't want/need that to go into ColumnTableReferenceUpdater again.
This should be a temporary fix; I believe we should revisit the general design around tables, ColumnExpression and TableReferenceExpression.
Finally, this isn't a super trivial fix - would appreciate a deep review (especially as we may consider this for patching).
Fixes #32234
Note that I ran into #26104 as well while testing this, which is a debug-only issue that's very related to this one (same SelectExpression instance referenced from multiple parts of the query).