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

The flag is_stat_field is not set for the min_value and max_value of field items
inside table share. This is a must requirement as we don't want to throw
warnings of truncation when we read values from the statistics table to the column
statistics of table share fields.

mysql-test/r/stat_tables.result

@@ -802,5 +802,28 @@ set use_stat_tables=@save_use_stat_tables;
 set @@histogram_size= @save_histogram_size;
 set @@optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity;
 drop table t1;
+#
+# MDEV-20589: Server still crashes in Field::set_warning_truncated_wrong_value
+#
+set names utf8;
+create table t1 ( a varchar(255) character set utf8);
+insert into t1 values (REPEAT('ӥ',255)), (REPEAT('ç',255));
+set use_stat_tables='preferably';
+analyze table t1 persistent for all;
+Table	Op	Msg_type	Msg_text
+test.t1	analyze	status	Engine-independent statistics collected
+test.t1	analyze	status	OK
+set @save_sql_mode= @@sql_mode;
+set sql_mode='ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION';
+update mysql.column_stats set min_value= REPEAT('ӥ',256) where db_name='test' and table_name='t1';
+Warnings:
+Warning	1265	Data truncated for column 'min_value' at row 1
+set @@sql_mode= @save_sql_mode;
+select length(a) from t1 where a=REPEAT('ӥ',255);
+length(a)
+510
+set names latin1;
+set @@use_stat_tables=@save_use_stat_tables;
+drop table t1;
 # please keep this at the last
 set @@global.histogram_size=@save_histogram_size;

mysql-test/r/stat_tables_innodb.result

@@ -829,6 +829,29 @@ set use_stat_tables=@save_use_stat_tables;
 set @@histogram_size= @save_histogram_size;
 set @@optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity;
 drop table t1;
+#
+# MDEV-20589: Server still crashes in Field::set_warning_truncated_wrong_value
+#
+set names utf8;
+create table t1 ( a varchar(255) character set utf8);
+insert into t1 values (REPEAT('ӥ',255)), (REPEAT('ç',255));
+set use_stat_tables='preferably';
+analyze table t1 persistent for all;
+Table	Op	Msg_type	Msg_text
+test.t1	analyze	status	Engine-independent statistics collected
+test.t1	analyze	status	OK
+set @save_sql_mode= @@sql_mode;
+set sql_mode='ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION';
+update mysql.column_stats set min_value= REPEAT('ӥ',256) where db_name='test' and table_name='t1';
+Warnings:
+Warning	1265	Data truncated for column 'min_value' at row 1
+set @@sql_mode= @save_sql_mode;
+select length(a) from t1 where a=REPEAT('ӥ',255);
+length(a)
+510
+set names latin1;
+set @@use_stat_tables=@save_use_stat_tables;
+drop table t1;
 # please keep this at the last
 set @@global.histogram_size=@save_histogram_size;
 set optimizer_switch=@save_optimizer_switch_for_stat_tables_test;

mysql-test/t/stat_tables.test

@@ -546,5 +546,27 @@ set @@histogram_size= @save_histogram_size;
 set @@optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity;
 drop table t1;
 
+--echo #
+--echo # MDEV-20589: Server still crashes in Field::set_warning_truncated_wrong_value
+--echo #
+
+set names utf8;
+create table t1 ( a varchar(255) character set utf8);
+insert into t1 values (REPEAT('ӥ',255)), (REPEAT('ç',255));
+
+set use_stat_tables='preferably';
+analyze table t1 persistent for all;
+
+set @save_sql_mode= @@sql_mode;
+set sql_mode='ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION';
+update mysql.column_stats set min_value= REPEAT('ӥ',256) where db_name='test' and table_name='t1';
+set @@sql_mode= @save_sql_mode;
+
+select length(a) from t1 where a=REPEAT('ӥ',255);
+
+set names latin1;
+set @@use_stat_tables=@save_use_stat_tables;
+drop table t1;
+
 --echo # please keep this at the last
 set @@global.histogram_size=@save_histogram_size;

sql/field.cc

@@ -2436,14 +2436,14 @@ 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 *tmp;
   if ((tmp= (Field*) memdup_root(root,(char*) this,size_of())))
   {
-    tmp->init(new_table);
+    if (new_table)
+      tmp->init(new_table);
     tmp->move_field_offset(diff);
   }
   tmp->is_stat_field= stat_flag;
@@ -2451,16 +2451,6 @@ Field *Field::clone(MEM_ROOT *root, TABLE *new_table, my_ptrdiff_t diff,
 }
 
 
-Field *Field::clone(MEM_ROOT *root, my_ptrdiff_t diff)
-{
-  Field *tmp;
-  if ((tmp= (Field*) memdup_root(root,(char*) this,size_of())))
-  {
-    tmp->move_field_offset(diff);
-  }
-  return tmp;
-}
-
 int Field::set_default()
 {
   if (default_value)

sql/field.h

@@ -1220,7 +1220,6 @@ class Field: public Value_source
   Field *clone(MEM_ROOT *mem_root, TABLE *new_table);
   Field *clone(MEM_ROOT *mem_root, TABLE *new_table, my_ptrdiff_t diff,
                bool stat_flag= FALSE);
-  Field *clone(MEM_ROOT *mem_root, my_ptrdiff_t diff);
   inline void move_field(uchar *ptr_arg,uchar *null_ptr_arg,uchar null_bit_arg)
   {
     ptr=ptr_arg; null_ptr=null_ptr_arg; null_bit=null_bit_arg;

sql/sql_statistics.cc

@@ -1153,12 +1153,14 @@ class Column_stat: public Stat_table
           case COLUMN_STAT_MIN_VALUE:
 	    table_field->read_stats->min_value->set_notnull();
             stat_field->val_str(&val);
+            DBUG_ASSERT(table_field->read_stats->min_value->is_stat_field);
             table_field->read_stats->min_value->store(val.ptr(), val.length(),
                                                       &my_charset_bin);
             break;
           case COLUMN_STAT_MAX_VALUE:
 	    table_field->read_stats->max_value->set_notnull();
             stat_field->val_str(&val);
+            DBUG_ASSERT(table_field->read_stats->min_value->is_stat_field);
             table_field->read_stats->max_value->store(val.ptr(), val.length(),
                                                       &my_charset_bin);
             break;
@@ -2045,7 +2047,7 @@ void create_min_max_statistical_fields_for_table_share(THD *thd,
         Field *fld;
         Field *table_field= *field_ptr;
         my_ptrdiff_t diff= record - table_share->default_values;
-        if (!(fld= table_field->clone(&stats_cb->mem_root, diff)))
+        if (!(fld= table_field->clone(&stats_cb->mem_root, NULL, diff, TRUE)))
           continue;
         if (i == 0)
           table_field->read_stats->min_value= fld;