Proper fix for disabling warnings in read_statistics_for_table().

MDEV-20589: Server still crashes in Field::set_warning_truncated_wrong_value

- Use dbug_tmp_use_all_columns() to mark that all fields can be used
- Remove field->is_stat_field (not needed)
- Remove extra arguments to Field::clone() that should not be there
- Safety fix for Field::set_warning_truncated_wrong_value() to not crash
  if table is zero in production builds (We have got crashes several times
  here so better to be safe than sorry).
- Threat wrong character string warnings identical to other field
  conversion warnings. This removes some warnings we before got from
  internal conversion errors.  There is no good reason why a user would
  get an error in case of 'key_field='wrong-utf8-string' but not for
  'field=wrong-utf8-string'.  The old code could also easily give
  thousands of no-sence warnings for one single statement.

1 files changed, 20 insertions, 15 deletions

diff --git a/sql/field.cc b/sql/field.cc
index 0d9797143fa..14d78433503 100644
--- a/sql/field.cc
+++ b/sql/field.cc
@@ -71,7 +71,7 @@ const char field_separator=',';
                   ptr < table->record[0] + table->s->reclength))))
 
 #define ASSERT_COLUMN_MARKED_FOR_WRITE_OR_COMPUTED                   \
-  DBUG_ASSERT(is_stat_field || !table ||                             \
+  DBUG_ASSERT(!table ||                             \
               (!table->write_set ||                                  \
                bitmap_is_set(table->write_set, field_index) ||       \
                (!(ptr >= table->record[0] &&                         \
@@ -2406,8 +2406,7 @@ Field *Field::clone(MEM_ROOT *root, TABLE *new_table)
 
 
 
-Field *Field::clone(MEM_ROOT *root, TABLE *new_table, my_ptrdiff_t diff,
-                    bool stat_flag)
+Field *Field::clone(MEM_ROOT *root, TABLE *new_table, my_ptrdiff_t diff)
 {
   Field *tmp;
   if ((tmp= (Field*) memdup_root(root,(char*) this,size_of())))
@@ -2415,7 +2414,6 @@ Field *Field::clone(MEM_ROOT *root, TABLE *new_table, my_ptrdiff_t diff,
     tmp->init(new_table);
     tmp->move_field_offset(diff);
   }
-  tmp->is_stat_field= stat_flag;
   return tmp;
 }
 
@@ -2853,7 +2851,7 @@ int Field_decimal::store(const char *from_arg, size_t len, CHARSET_INFO *cs)
   
   /*
     Write digits of the frac_% parts ;
-    Depending on get_thd()->count_cutted_fields, we may also want
+    Depending on get_thd()->count_cuted_fields, we may also want
     to know if some non-zero tail of these parts will
     be truncated (for example, 0.002->0.00 will generate a warning,
     while 0.000->0.00 will not)
@@ -6991,7 +6989,8 @@ Field_longstr::check_string_copy_error(const String_copier *copier,
   if (likely(!(pos= copier->most_important_error_pos())))
     return FALSE;
 
-  if (!is_stat_field)
+  /* Ignore errors from internal expressions */
+  if (get_thd()->count_cuted_fields > CHECK_FIELD_EXPRESSION)
   {
     convert_to_printable(tmp, sizeof(tmp), pos, (end - pos), cs, 6);
     set_warning_truncated_wrong_value("string", tmp);
@@ -7024,8 +7023,9 @@ int
 Field_longstr::report_if_important_data(const char *pstr, const char *end,
                                         bool count_spaces)
 {
-  THD *thd= get_thd();
-  if ((pstr < end) && thd->count_cuted_fields > CHECK_FIELD_EXPRESSION)
+  THD *thd;
+  if ((pstr < end) &&
+      (thd= get_thd())->count_cuted_fields > CHECK_FIELD_EXPRESSION)
   {
     if (test_if_important_data(field_charset, pstr, end))
     {
@@ -7036,7 +7036,8 @@ Field_longstr::report_if_important_data(const char *pstr, const char *end,
       return 2;
     }
     else if (count_spaces)
-    { /* If we lost only spaces then produce a NOTE, not a WARNING */
+    {
+      /* If we lost only spaces then produce a NOTE, not a WARNING */
       set_note(WARN_DATA_TRUNCATED, 1);
       return 2;
     }
@@ -11381,13 +11382,17 @@ void Field::set_warning_truncated_wrong_value(const char *type_arg,
                                               const char *value)
 {
   THD *thd= get_thd();
-  const char *db_name= table->s->db.str;
-  const char *table_name= table->s->table_name.str;
+  const char *db_name;
+  const char *table_name;
+  /*
+    table has in the past been 0 in case of wrong calls when processing
+    statistics tables. Let's protect against that.
+  */
+  DBUG_ASSERT(table);
 
-  if (!db_name)
-    db_name= "";
-  if (!table_name)
-    table_name= "";
+  db_name= (table && table->s->db.str) ? table->s->db.str : "";
+  table_name= ((table && table->s->table_name.str) ? table->s->table_name.str :
+	       "");
 
   push_warning_printf(thd, Sql_condition::WARN_LEVEL_WARN,
                       ER_TRUNCATED_WRONG_VALUE_FOR_FIELD,