MDEV-9709 Unexpected modification of value and warning about out of range value upon ALTER

MDEV-4102 Limitation on DOUBLE or REAL length is ignored with INSERT .. SELECT

1 files changed, 10 insertions, 0 deletions

diff --git a/sql/field.h b/sql/field.h
index 8869c16cb98..3c6e318f270 100644
--- a/sql/field.h
+++ b/sql/field.h
@@ -1707,6 +1707,16 @@ public:
     return do_field_real;
   }
   int save_in_field(Field *to) { return to->store(val_real()); }
+  bool memcpy_field_possible(const Field *from) const
+  {
+    /*
+      Cannot do memcpy from a longer field to a shorter field,
+      e.g. a DOUBLE(53,10) into a DOUBLE(10,10).
+      But it should be OK the other way around.
+    */
+    return Field_num::memcpy_field_possible(from) &&
+           field_length >= from->field_length;
+  }
   int store_decimal(const my_decimal *);
   int  store_time_dec(MYSQL_TIME *ltime, uint dec);
   bool get_date(MYSQL_TIME *ltime, ulonglong fuzzydate);