[release/9.0] Fix TPC equality check inside subquery predicate (#35120) #35201
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Fixes #35118
Port of #35120
Description
The deep query pipeline re-architecting in 9.0 included turning our SQL expression tree into a real tree rather than a graph, i.e. removing cycles where a SQL table was referenced both from its containing SelectExpression, and from any referencing columns. As a result, a changed predicate check for TPC inheritance was broken and did not correctly access the column's table when the column was nested in a subquery and referenced an outer table.
Customer impact
LINQ queries including a minimal equality predicate where a column references an outer table are now broken. For example:
These queries are sufficiently common, and the fix sufficiently simple, that servicing seems justified.
How found
Customer reported on 9.0.0
Regression
Yes, from 8.0.
Testing
Test added.
Risk
Low, quirk added.