MDEV-22509: Server crashes in Field_inet6::store_inet6_null_with_warn / Field::maybe_null

For field with type INET, during EITS collection the min and max values are store in text
representation in the statistical table.
While retrieving the value from the statistical table, the value is stored back in the original
field using binary form instead of text and this was resulting in the crash.

Introduced 2 functions in the Field structure:
  1) store_to_statistical_minmax_field
  2) store_from_statistical_minmax_field

1 files changed, 22 insertions, 16 deletions

diff --git a/sql/sql_statistics.cc b/sql/sql_statistics.cc
index f51f63020a3..0598698f7e5 100644
--- a/sql/sql_statistics.cc
+++ b/sql/sql_statistics.cc
@@ -1036,27 +1036,31 @@ public:
         stat_field->set_notnull();
         switch (i) {
         case COLUMN_STAT_MIN_VALUE:
+        {
+          /*
+            TODO varun: After MDEV-22583 is fixed, add a function in Field_bit
+            and move this implementation there
+          */
           if (table_field->type() == MYSQL_TYPE_BIT)
             stat_field->store(table_field->collected_stats->min_value->val_int(),true);
           else
           {
-            table_field->collected_stats->min_value->val_str(&val);
-            size_t length= Well_formed_prefix(val.charset(), val.ptr(),
-                           MY_MIN(val.length(), stat_field->field_length)).length();
-            stat_field->store(val.ptr(), length, &my_charset_bin);
+            Field *field= table_field->collected_stats->min_value;
+            field->store_to_statistical_minmax_field(stat_field, &val);
           }
           break;
+        }
         case COLUMN_STAT_MAX_VALUE:
+        {
           if (table_field->type() == MYSQL_TYPE_BIT)
             stat_field->store(table_field->collected_stats->max_value->val_int(),true);
           else
           {
-            table_field->collected_stats->max_value->val_str(&val);
-            size_t length= Well_formed_prefix(val.charset(), val.ptr(),
-                            MY_MIN(val.length(), stat_field->field_length)).length();
-            stat_field->store(val.ptr(), length, &my_charset_bin);
+            Field *field= table_field->collected_stats->max_value;
+            field->store_to_statistical_minmax_field(stat_field, &val);
           }
           break;
+        }
         case COLUMN_STAT_NULLS_RATIO:
           stat_field->store(table_field->collected_stats->get_nulls_ratio());
           break;
@@ -1133,17 +1137,19 @@ public:
 
           switch (i) {
           case COLUMN_STAT_MIN_VALUE:
-	    table_field->read_stats->min_value->set_notnull();
-            stat_field->val_str(&val);
-            table_field->read_stats->min_value->store(val.ptr(), val.length(),
-                                                      &my_charset_bin);
+          {
+            Field *field= table_field->read_stats->min_value;
+            field->set_notnull();
+            field->store_from_statistical_minmax_field(stat_field, &val);
             break;
+          }
           case COLUMN_STAT_MAX_VALUE:
-	    table_field->read_stats->max_value->set_notnull();
-            stat_field->val_str(&val);
-            table_field->read_stats->max_value->store(val.ptr(), val.length(),
-                                                      &my_charset_bin);
+          {
+            Field *field= table_field->read_stats->max_value;
+            field->set_notnull();
+            field->store_from_statistical_minmax_field(stat_field, &val);
             break;
+          }
           case COLUMN_STAT_NULLS_RATIO:
             table_field->read_stats->set_nulls_ratio(stat_field->val_real());
             break;