MDEV-28020 CHECKSUM TABLE calculates different checksums

Two bugs here:

1. CHECKSUM TABLE asserted that all fields in the table are arranged
   sequentially in the record, but virtual columns are always at the
   end, violating this assertion
2. virtual columns were not calculated for CHECKSUM, so CHECKSUM
   was using, essentially, garbage left from the previous statement.
   (that's why the test must use INSERT IGNORE to have this "previous
   statement" mark vcols not null)

Fix: don't include virtual columns into the table CHECKSUM. Indeed,
they cannot be included as the engine does not see virtual columns,
so in-engine checksum cannot include them, meaning in-server checksum
should not either

mysql-test/r/row-checksum-old.result

@@ -1,4 +1,3 @@
-drop table if exists t1;
 create table t1 (a int null, v varchar(100)) engine=myisam checksum=0;
 insert into t1 values(null, null), (1, "hello");
 checksum table t1;
@@ -98,4 +97,48 @@ CHECKSUM TABLE t1 EXTENDED;
 Table	Checksum
 test.t1	2326430205
 drop table t1;
+#
 # End of 5.5 tests
+#
+#
+# MDEV-28020 CHECKSUM TABLE calculates different checksums
+#
+create table t1 ( a int, b int as (a) virtual, c text) engine=myisam checksum=1;
+insert ignore t1 values (1,2,'foo'),(2,3,'bar');
+Warnings:
+Warning	1906	The value specified for generated column 'b' in table 't1' has been ignored
+Warning	1906	The value specified for generated column 'b' in table 't1' has been ignored
+checksum table t1 extended;
+Table	Checksum
+test.t1	4101438232
+checksum table t1;
+Table	Checksum
+test.t1	4101438232
+drop table t1;
+create table t1 ( a int, b int as (a) virtual, c text, key(b)) engine=myisam checksum=1;
+insert ignore t1 values (1,2,'foo'),(2,3,'bar');
+Warnings:
+Warning	1906	The value specified for generated column 'b' in table 't1' has been ignored
+Warning	1906	The value specified for generated column 'b' in table 't1' has been ignored
+checksum table t1 extended;
+Table	Checksum
+test.t1	4101438232
+checksum table t1;
+Table	Checksum
+test.t1	4101438232
+drop table t1;
+create table t1 ( a int, b int as (a) stored, c text) engine=myisam checksum=1;
+insert ignore t1 values (1,2,'foo'),(2,3,'bar');
+Warnings:
+Warning	1906	The value specified for generated column 'b' in table 't1' has been ignored
+Warning	1906	The value specified for generated column 'b' in table 't1' has been ignored
+checksum table t1 extended;
+Table	Checksum
+test.t1	2897795735
+checksum table t1;
+Table	Checksum
+test.t1	2897795735
+drop table t1;
+#
+# End of 10.2 tests
+#

mysql-test/r/row-checksum.result

@@ -1,4 +1,3 @@
-drop table if exists t1;
 create table t1 (a int null, v varchar(100)) engine=myisam checksum=0;
 insert into t1 values(null, null), (1, "hello");
 checksum table t1;
@@ -98,4 +97,48 @@ CHECKSUM TABLE t1 EXTENDED;
 Table	Checksum
 test.t1	2326430205
 drop table t1;
+#
 # End of 5.5 tests
+#
+#
+# MDEV-28020 CHECKSUM TABLE calculates different checksums
+#
+create table t1 ( a int, b int as (a) virtual, c text) engine=myisam checksum=1;
+insert ignore t1 values (1,2,'foo'),(2,3,'bar');
+Warnings:
+Warning	1906	The value specified for generated column 'b' in table 't1' has been ignored
+Warning	1906	The value specified for generated column 'b' in table 't1' has been ignored
+checksum table t1 extended;
+Table	Checksum
+test.t1	4101438232
+checksum table t1;
+Table	Checksum
+test.t1	4101438232
+drop table t1;
+create table t1 ( a int, b int as (a) virtual, c text, key(b)) engine=myisam checksum=1;
+insert ignore t1 values (1,2,'foo'),(2,3,'bar');
+Warnings:
+Warning	1906	The value specified for generated column 'b' in table 't1' has been ignored
+Warning	1906	The value specified for generated column 'b' in table 't1' has been ignored
+checksum table t1 extended;
+Table	Checksum
+test.t1	4101438232
+checksum table t1;
+Table	Checksum
+test.t1	4101438232
+drop table t1;
+create table t1 ( a int, b int as (a) stored, c text) engine=myisam checksum=1;
+insert ignore t1 values (1,2,'foo'),(2,3,'bar');
+Warnings:
+Warning	1906	The value specified for generated column 'b' in table 't1' has been ignored
+Warning	1906	The value specified for generated column 'b' in table 't1' has been ignored
+checksum table t1 extended;
+Table	Checksum
+test.t1	2897795735
+checksum table t1;
+Table	Checksum
+test.t1	2897795735
+drop table t1;
+#
+# End of 10.2 tests
+#

mysql-test/t/row-checksum.test

@@ -2,12 +2,8 @@
 # Test checksum
 #
 
--- source include/have_innodb.inc
--- source include/have_maria.inc
-
---disable_warnings
-drop table if exists t1;
---enable_warnings
+--source include/have_innodb.inc
+--source include/have_maria.inc
 
 create table t1 (a int null, v varchar(100)) engine=myisam checksum=0;
 insert into t1 values(null, null), (1, "hello");
@@ -76,4 +72,31 @@ CHECKSUM TABLE t1 EXTENDED;
 
 drop table t1;
 
+--echo #
 --echo # End of 5.5 tests
+--echo #
+
+--echo #
+--echo # MDEV-28020 CHECKSUM TABLE calculates different checksums
+--echo #
+create table t1 ( a int, b int as (a) virtual, c text) engine=myisam checksum=1;
+insert ignore t1 values (1,2,'foo'),(2,3,'bar');
+checksum table t1 extended;
+checksum table t1;
+drop table t1;
+
+create table t1 ( a int, b int as (a) virtual, c text, key(b)) engine=myisam checksum=1;
+insert ignore t1 values (1,2,'foo'),(2,3,'bar');
+checksum table t1 extended;
+checksum table t1;
+drop table t1;
+
+create table t1 ( a int, b int as (a) stored, c text) engine=myisam checksum=1;
+insert ignore t1 values (1,2,'foo'),(2,3,'bar');
+checksum table t1 extended;
+checksum table t1;
+drop table t1;
+
+--echo #
+--echo # End of 10.2 tests
+--echo #

sql/sql_table.cc

@@ -10631,6 +10631,8 @@ bool mysql_checksum_table(THD *thd, TABLE_LIST *tables,
             for (uint i= 0; i < t->s->fields; i++ )
             {
               Field *f= t->field[i];
+              if (!f->stored_in_db())
+                continue;
 
               if (! thd->variables.old_mode && f->is_real_null(0))
               {