Dave Gosselin db8ec28147 MDEV-40573: Crash on multi-table DELETE with an impossible WHERE ...

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.

2026-09-25 10:49:28 -04:00

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