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

mysql-test/r/trigger.result

@@ -2087,4 +2087,21 @@ ERROR 42S02: Table 'test.a_nonextisting_table' doesn't exist
 SELECT * FROM t2;
 a	b
 DROP TABLE t1, t2;
+CREATE TABLE t1 (id INT NOT NULL);
+CREATE TABLE t2 (id INT NOT NULL);
+INSERT t1 VALUES (1),(2),(3);
+UPDATE t1 SET id=NULL;
+Warnings:
+Warning	1048	Column 'id' cannot be null
+Warning	1048	Column 'id' cannot be null
+Warning	1048	Column 'id' cannot be null
+CREATE TRIGGER t1_bu BEFORE UPDATE ON t1 FOR EACH ROW
+INSERT INTO t2 VALUES (3);
+UPDATE t1 SET id=NULL;
+Warnings:
+Warning	1048	Column 'id' cannot be null
+Warning	1048	Column 'id' cannot be null
+Warning	1048	Column 'id' cannot be null
+DROP TRIGGER t1_bu;
+DROP TABLE t1,t2;
 End of 5.1 tests.

mysql-test/t/trigger.test

@@ -2396,4 +2396,17 @@ SELECT * FROM t2;
 
 DROP TABLE t1, t2;
 
+#
+# Bug #48525: trigger changes "Column 'id' cannot be null" behaviour
+#
+CREATE TABLE t1 (id INT NOT NULL);
+CREATE TABLE t2 (id INT NOT NULL);
+INSERT t1 VALUES (1),(2),(3);
+UPDATE t1 SET id=NULL;
+CREATE TRIGGER t1_bu BEFORE UPDATE ON t1 FOR EACH ROW
+  INSERT INTO t2 VALUES (3);
+UPDATE t1 SET id=NULL;
+DROP TRIGGER t1_bu;
+DROP TABLE t1,t2;
+
 --echo End of 5.1 tests.

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;
 }
 

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));
 }
 

sql/sql_class.cc

@@ -3100,6 +3100,7 @@ void THD::reset_sub_statement_state(Sub_statement_state *backup,
   }
 #endif
   
+  backup->count_cuted_fields= count_cuted_fields;
   backup->options=         options;
   backup->in_sub_stmt=     in_sub_stmt;
   backup->enable_slow_log= enable_slow_log;
@@ -3137,6 +3138,7 @@ void THD::reset_sub_statement_state(Sub_statement_state *backup,
 
 void THD::restore_sub_statement_state(Sub_statement_state *backup)
 {
+  DBUG_ENTER("THD::restore_sub_statement_state");
 #ifndef EMBEDDED_LIBRARY
   /* BUG#33029, if we are replicating from a buggy master, restore
      auto_inc_intervals_forced so that the top statement can use the
@@ -3163,6 +3165,7 @@ void THD::restore_sub_statement_state(Sub_statement_state *backup)
     /* ha_release_savepoint() never returns error. */
     (void)ha_release_savepoint(this, sv);
   }
+  count_cuted_fields= backup->count_cuted_fields;
   transaction.savepoints= backup->savepoints;
   options=          backup->options;
   in_sub_stmt=      backup->in_sub_stmt;
@@ -3192,6 +3195,7 @@ void THD::restore_sub_statement_state(Sub_statement_state *backup)
   */
   examined_row_count+= backup->examined_row_count;
   cuted_fields+=       backup->cuted_fields;
+  DBUG_VOID_RETURN;
 }
 
 

sql/sql_class.h

@@ -995,6 +995,7 @@ public:
   bool enable_slow_log;
   bool last_insert_id_used;
   SAVEPOINT *savepoints;
+  enum enum_check_fields count_cuted_fields;
 };
 
 

sql/sql_insert.cc

@@ -3158,7 +3158,7 @@ bool select_insert::send_data(List<Item> &values)
 
   thd->count_cuted_fields= CHECK_FIELD_WARN;	// Calculate cuted fields
   store_values(values);
-  thd->count_cuted_fields= CHECK_FIELD_IGNORE;
+  thd->count_cuted_fields= CHECK_FIELD_ERROR_FOR_NULL;
   if (thd->is_error())
   {
     table->auto_increment_field_not_null= FALSE;