Bug#12296 - CHECKSUM TABLE reports 0 for the table

Skipping deleted records instead of breaking the loop
during checksum calculation.

mysql-test/r/myisam.result

@@ -595,3 +595,17 @@ show keys from t1;
 Table	Non_unique	Key_name	Seq_in_index	Column_name	Collation	Cardinality	Sub_part	Packed	Null	Index_type	Comment
 t1	1	a	1	a	A	8	NULL	NULL	YES	BTREE	
 drop table t1;
+create table t1 (c1 int);
+insert into t1 values (1),(2),(3),(4);
+checksum table t1;
+Table	Checksum
+test.t1	149057747
+delete from t1 where c1 = 1;
+create table t2 as select * from t1;
+checksum table t1;
+Table	Checksum
+test.t1	984116287
+checksum table t2;
+Table	Checksum
+test.t2	984116287
+drop table t1, t2;

mysql-test/t/myisam.test

@@ -575,4 +575,19 @@ show keys from t1;
 
 drop table t1;
 
+#
+# Bug#12296 - CHECKSUM TABLE reports 0 for the table
+# This happened if the first record was marked as deleted.
+#
+create table t1 (c1 int);
+insert into t1 values (1),(2),(3),(4);
+checksum table t1;
+delete from t1 where c1 = 1;
+create table t2 as select * from t1;
+# The following returns 0 with the bug in place.
+checksum table t1;
+# The above should give the same number as the following.
+checksum table t2;
+drop table t1, t2;
+
 # End of 4.1 tests

sql/sql_table.cc

@@ -3745,9 +3745,16 @@ int mysql_checksum_table(THD *thd, TABLE_LIST *tables, HA_CHECK_OPT *check_opt)
 	  protocol->store_null();
 	else
 	{
-	  while (!t->file->rnd_next(t->record[0]))
+	  for (;;)
 	  {
 	    ha_checksum row_crc= 0;
+            int error= t->file->rnd_next(t->record[0]);
+            if (unlikely(error))
+            {
+              if (error == HA_ERR_RECORD_DELETED)
+                continue;
+              break;
+            }
 	    if (t->record[0] != (byte*) t->field[0]->ptr)
 	      row_crc= my_checksum(row_crc, t->record[0],
 				   ((byte*) t->field[0]->ptr) - t->record[0]);