MDEV-40573: Crash on multi-table DELETE with an impossible WHERE - #5478
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MDEV-40573: Crash on multi-table DELETE with an impossible WHERE#5478DaveGosselin-MariaDB wants to merge 1 commit into
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A DELETE containing a single table, an index hint, an impossible WHERE condition, and a window function will take the multi-delete code path but never initialize tables for deletion, leading to a crash. Such a statement would never delete rows from the target table. Record in the multi_delete whether it was ever initialized for execution, and don't attempt to delete anything if it wasn't initialized. The index hint forces the single table DELETE to take the multi-table codepath. Since this case has an impossible WHERE condition, we set subq_exit_fl which later causes JOIN::optimize_stage2 to skip the multi-delete table initialization. It's not safe to attempt initialization when trying to find a "tableless" subquery plan, so defend against this case with the new multi-delete flag added by this commit.
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A DELETE containing a single table, an index hint, an impossible WHERE condition, and a window function will take the multi-delete code path but never initialize tables for deletion, leading to a crash. Such a statement would never delete rows from the target table. Record in the multi_delete whether it was ever initialized for execution, and don't attempt to delete anything if it wasn't initialized.
The index hint forces the single table DELETE to take the multi-table codepath. Since this case has an impossible WHERE condition, we set subq_exit_fl which later causes JOIN::optimize_stage2 to skip the multi-delete table initialization. It's not safe to attempt initialization when trying to find a "tableless" subquery plan, so defend against this case with the new multi-delete flag added by this commit.