Bug#48525: trigger changes "Column 'id' cannot be null" behaviour

CHECK_FIELD_IGNORE was treated as CHECK_FIELD_ERROR_FOR_NULL;
UPDATE...SET...NULL on NOT NULL fields behaved differently after
a trigger.

Now distinguishes between IGNORE and ERROR_FOR_NULL and save/restores
check-field options.

mysql-test/r/trigger.result:
  Show that UPDATE...SET...NULL on NOT NULL columns doesn't behave differently
  when run after a trigger.
mysql-test/t/trigger.test:
  Show that UPDATE...SET...NULL on NOT NULL columns doesn't behave differently
  when run after a trigger.
sql/field_conv.cc:
  CHECK_FIELD_IGNORE was treated as CHECK_FIELD_ERROR_FOR_NULL.
  Distinguish between the two.
sql/sp_head.cc:
  raise error as needed
sql/sql_class.cc:
  Save and restore check-fields options.
sql/sql_class.h:
  Make room so we can save check-fields options.
sql/sql_insert.cc:
  raise error as needed

1 files changed, 1 insertions, 0 deletions

diff --git a/sql/sp_head.cc b/sql/sp_head.cc
index 8a626cabd90..11d5e5f830b 100644
--- a/sql/sp_head.cc
+++ b/sql/sp_head.cc
@@ -3009,6 +3009,7 @@ int
 sp_instr_set_trigger_field::execute(THD *thd, uint *nextp)
 {
   DBUG_ENTER("sp_instr_set_trigger_field::execute");
+  thd->count_cuted_fields= CHECK_FIELD_ERROR_FOR_NULL;
   DBUG_RETURN(m_lex_keeper.reset_lex_and_exec_core(thd, nextp, TRUE, this));
 }