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Since the original implementation of CTEs only allowed them in SELECT queries, the rule rewriter did not expect to find any CTEs in statements being rewritten by ON INSERT/UPDATE/DELETE rules. We had dealt with this to some extent but the code was still several bricks shy of a load, as illustrated in bug #6051 from Jehan-Guillaume de Rorthais. In particular, we have to be able to copy CTEs from the original query's cteList into that of a rule action, in case the rule action references the CTE (which it pretty much always will). This also implies we were doing things in the wrong order in RewriteQuery: we have to recursively rewrite the CTE queries before expanding the main query, so that we have the rewritten queries available to copy. There are unpleasant limitations yet to resolve here, but at least we now throw understandable FEATURE_NOT_SUPPORTED errors for them instead of just failing with bizarre implementation-dependent errors. In particular, we can't handle propagating the same CTE into multiple post-rewrite queries (because then the CTE would be evaluated multiple times), and we can't cope with conflicts between CTE names in the original query and in the rule actions. |
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