On Fri, 17 Apr 2026 at 21:04, SATYANARAYANA NARLAPURAM <satyanarlapuram@gmail.com> wrote: > > Hi hackers, > > UPDATE and DELETE with WHERE CURRENT OF cursor fail on tables that have virtual generated columns, erroring with "WHERE CURRENT OF on a view is not implemented" even though the target is a regular table, not a view. >
Nice catch!
> Analysis: > The bug stems from replace_rte_variables_mutator() in rewriteManip.c, which unconditionally errors on any CurrentOfExpr referencing the target relation. This appears to a check designed for view rewriting, where WHERE CURRENT OF cannot be translated through a view. However, virtual generated column (VGC) expansion also routes through this mutator. The rewriter's expand_generated_columns_internal() calls ReplaceVarsFromTargetList(), and the planner's expand_virtual_generated_columns() calls pullup_replace_vars(), which calls replace_rte_variables(). Since virtual generated columns use same mutator, while expanding virtual generated columns returns the same error even though the table is not a view and the cursor position is perfectly valid. > > The fix adds bool error_on_current_of to replace_rte_variables_context. The existing replace_rte_variables() is refactored into a static replace_rte_variables_internal() that accepts the flag, with two public wrappers: replace_rte_variables() (passes true, preserving existing behavior) and replace_rte_variables_ext() (exposes the flag). The same pattern is applied to ReplaceVarsFromTargetList() / ReplaceVarsFromTargetListExtended(). In replace_rte_variables_mutator(), the CurrentOfExpr error is now conditional on context->error_on_current_of. The two VGC expansion call sites pass false; all other callers pass true. The down side of this approach is that it is adding additional public API. >
Hmm, it seems to me that a much simpler fix is to check for use of WHERE CURRENT OF on a view at parse time, and throw the error there.
This patch looks simple and neat, is there any reason why it was done differently earlier?
Then the problematic rewriter check can simply be removed, as in the attached v2 patch.
I reviewed the patch, and it addresses the original bug and other existing tests.
I verified it rejects the view with WHERE CURRENT OF on update and delete.
Updated the patch to include a test case to reject view update with WHERE CURRENT OF.
