1 files changed, 15 insertions, 1 deletions
diff --git a/sql/sql_lex.cc b/sql/sql_lex.cc
index 125bbfe1bfd..47ff2836aba 100644
--- a/sql/sql_lex.cc
+++ b/sql/sql_lex.cc
@@ -3898,7 +3898,21 @@ bool st_select_lex::optimize_unflattened_subqueries(bool const_only)
       }
       if (empty_union_result)
         subquery_predicate->no_rows_in_result();
-      if (!is_correlated_unit)
+
+      if (is_correlated_unit)
+      {
+        /*
+          Some parts of UNION are not correlated. This means we will need to
+          re-execute the whole UNION every time. Mark all parts of the UNION
+          as correlated so that they are prepared to be executed multiple
+          times (if we don't do that, some part of the UNION may free its
+          execution data at the end of first execution and crash on the second
+          execution)
+        */
+        for (SELECT_LEX *sl= un->first_select(); sl; sl= sl->next_select())
+          sl->uncacheable |= UNCACHEABLE_DEPENDENT;
+      }
+      else
         un->uncacheable&= ~UNCACHEABLE_DEPENDENT;
       subquery_predicate->is_correlated= is_correlated_unit;
     }