Can we include the CustomScan node in the list of nodes that do not
support projection?
Reason is that custom node can contain quite arbitrary logic that does
not guarantee projection support.
Secondly. If planner does not need a separate Result node, it just
assign tlist to subplan (i.e. changes targetlist of custom node) and
does not change the custom_scan_tlist.
Perhaps I do not fully understand the logic of using the
custom_scan_tlist field. But if into the PlanCustomPath() routine our
custom node does not build own custom_scan_tlist (may be it will use
tlist as base for custom_scan_tlist) we will get errors in the
set_customscan_references() call.
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Andrey Lepikhov
Postgres Professional
https://postgrespro.com
The Russian Postgres Company
