Aleksey Midenkov 9f70e0a76c MDEV-32299 Segfault when preparing unreferenced select in recursive CTE ...

With_element::prepare_unreferenced() contains query from recursive CTE
which is upper owner of unreferenced CTE itself. Such recursive
derived table is resolved into its expression and it tries to resolve
fields or any other data from subqueries which are not yet
prepared. These subqueries are preparing in upper frames of the same
stack after prepare_unreferenced() finishes.

That does not happen when recursion happens in referenced CTE because
in that case there are links between the derived tables defined by the
parser and descending into such recursion descends further into all
the dependency queries. No such link exists in unreferenced query
therefore it misses its upper dependencies.

The fix moves prepare_unreferenced() later after JOIN::prepare() so it
has the chance to access all the prepared data.

There may be another fix of failing unreferenced queries with error as
such kind of queries seem to be not usable.

2025-12-23 13:42:45 +03:00

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