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, 18 insertions, 8 deletions

diff --git a/sql/field_conv.cc b/sql/field_conv.cc
index 3574534722e..0bffde9671a 100644
--- a/sql/field_conv.cc
+++ b/sql/field_conv.cc
@@ -122,13 +122,18 @@ set_field_to_null(Field *field)
     return 0;
   }
   field->reset();
-  if (field->table->in_use->count_cuted_fields == CHECK_FIELD_WARN)
-  {
+  switch (field->table->in_use->count_cuted_fields) {
+  case CHECK_FIELD_WARN:
     field->set_warning(MYSQL_ERROR::WARN_LEVEL_WARN, WARN_DATA_TRUNCATED, 1);
+    /* fall through */
+  case CHECK_FIELD_IGNORE:
     return 0;
+  case CHECK_FIELD_ERROR_FOR_NULL:
+    if (!field->table->in_use->no_errors)
+      my_error(ER_BAD_NULL_ERROR, MYF(0), field->field_name);
+    return -1;
   }
-  if (!field->table->in_use->no_errors)
-    my_error(ER_BAD_NULL_ERROR, MYF(0), field->field_name);
+  DBUG_ASSERT(0); // impossible
   return -1;
 }
 
@@ -178,13 +183,18 @@ set_field_to_null_with_conversions(Field *field, bool no_conversions)
     field->table->auto_increment_field_not_null= FALSE;
     return 0;				  // field is set in fill_record()
   }
-  if (field->table->in_use->count_cuted_fields == CHECK_FIELD_WARN)
-  {
+  switch (field->table->in_use->count_cuted_fields) {
+  case CHECK_FIELD_WARN:
     field->set_warning(MYSQL_ERROR::WARN_LEVEL_WARN, ER_BAD_NULL_ERROR, 1);
+    /* fall through */
+  case CHECK_FIELD_IGNORE:
     return 0;
+  case CHECK_FIELD_ERROR_FOR_NULL:
+    if (!field->table->in_use->no_errors)
+      my_error(ER_BAD_NULL_ERROR, MYF(0), field->field_name);
+    return -1;
   }
-  if (!field->table->in_use->no_errors)
-    my_error(ER_BAD_NULL_ERROR, MYF(0), field->field_name);
+  DBUG_ASSERT(0); // impossible
   return -1;
 }