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

plugin/type_inet/mysql-test/type_inet/type_inet6_stat_tables.result

@@ -13,5 +13,19 @@ test.t1	analyze	status	OK
 INSERT INTO t1 VALUES ('3::3');
 DROP TABLE t1;
 #
+# MDEV-22509: Server crashes in Field_inet6::store_inet6_null_with_warn / Field::maybe_null
+#
+CREATE TABLE t1 (a INT, b INET6 NOT NULL);
+INSERT INTO t1 VALUES (1,'::'),(2,'::');
+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
+SELECT t1.a from t1;
+a
+1
+2
+DROP TABLE t1;
+#
 # End of 10.5 tests
 #

plugin/type_inet/mysql-test/type_inet/type_inet6_stat_tables.test

@@ -14,6 +14,16 @@ ANALYZE TABLE t1 PERSISTENT FOR ALL;
 INSERT INTO t1 VALUES ('3::3');
 DROP TABLE t1;
 
+--echo #
+--echo # MDEV-22509: Server crashes in Field_inet6::store_inet6_null_with_warn / Field::maybe_null
+--echo #
+
+CREATE TABLE t1 (a INT, b INET6 NOT NULL);
+INSERT INTO t1 VALUES (1,'::'),(2,'::');
+ANALYZE TABLE t1 PERSISTENT FOR ALL;
+SELECT t1.a from t1;
+DROP TABLE t1;
+
 --echo #
 --echo # End of 10.5 tests
 --echo #

sql/field.cc

@@ -1967,6 +1967,23 @@ int Field::store_timestamp_dec(const timeval &ts, uint dec)
   return store_time_dec(Datetime(get_thd(), ts).get_mysql_time(), dec);
 }
 
+
+int Field::store_to_statistical_minmax_field(Field *field, String *val)
+{
+  val_str(val);
+  size_t length= Well_formed_prefix(val->charset(), val->ptr(),
+                 MY_MIN(val->length(), field->field_length)).length();
+  return field->store(val->ptr(), length, &my_charset_bin);
+}
+
+
+int Field::store_from_statistical_minmax_field(Field *stat_field, String *str)
+{
+  stat_field->val_str(str);
+  return store_text(str->ptr(), str->length(), &my_charset_bin);
+}
+
+
 /**
    Pack the field into a format suitable for storage and transfer.
 

sql/field.h

@@ -978,6 +978,24 @@ class Field: public Value_source
     return store(ls.str, (uint) ls.length, cs);
   }
 
+  /*
+    @brief
+      Store minimum/maximum value of a column in the statistics table.
+    @param
+      field                  statistical table field
+      str                    value buffer
+  */
+  virtual int store_to_statistical_minmax_field(Field *field, String *str);
+
+  /*
+    @brief
+      Store minimum/maximum value of a column from the statistical table.
+    @param
+      field                  statistical table field
+      str                    value buffer
+  */
+  virtual int store_from_statistical_minmax_field(Field *field, String *str);
+
 #ifdef HAVE_valgrind_or_MSAN
   /**
     Mark unused memory in the field as defined. Mainly used to ensure

sql/sql_statistics.cc

@@ -1036,27 +1036,31 @@ class Column_stat: public Stat_table
         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 @@ class Column_stat: public Stat_table
 
           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;