fix: the results of tikv and tiflash are different (#5839)

dbms/src/Functions/FunctionsLogical.h

@@ -184,7 +184,23 @@ struct AssociativeOperationImpl
     {
         if (Op::isSaturable())
         {
-            UInt8 a = vec[i];
+            // cast a: UInt8 -> bool -> UInt8 is a trick
+            // TiFlash converts columns with non-UInt8 type to UInt8 type and sets value to 0 or 1
+            // which correspond to false or true. However, for columns with UInt8 type,
+            // no more convertion will be executed on them and the values stored
+            // in them are 'origin' which means that they won't be converted to 0 or 1.
+            // For example:
+            //   Input column with non-UInt8 type:
+            //      column_values = {-2, 0, 2}
+            //   then, they will be converted to:
+            //      vec = {1, 0, 1} (here vec stores converted values)
+            //
+            //   Input column with UInt8 type:
+            //      column_values = {1, 0, 2}
+            //   then, the vec will be:
+            //      vec = {1, 0, 2} (error, we only want 0 or 1)
+            // See issue: https://github.com/pingcap/tidb/issues/37258
+            bool a = static_cast<bool>(vec[i]);
             return Op::isSaturatedValue(a) ? a : continuation.apply(i);
         }
         else

tests/fullstack-test/expr/logical_op.test

@@ -1,19 +1,24 @@
 mysql> drop table if exists test.t1;
 mysql> drop table if exists test.t2;
 mysql> drop table if exists test.t3;
+mysql> drop table if exists test.t4;
 mysql> create table test.t1(a char(20),b double);
 mysql> create table test.t2(a char(20));
 mysql> create table test.t3(a int);
+mysql> create table test.t4(a tinyint(45) unsigned NOT NULL, b bigint(20) NOT NULL);
 mysql> insert into test.t1 values(1,null),('j',0),(1,12.991),(0,0),(0,0),('they',1.009),('can',-99),(0,12.991),(1,-9.183),(null,1);
 mysql> insert into test.t2 values(0),(0),(0),(0),(0),(0),(1),('with'),('see'),(null);
 mysql> insert into test.t3 values(0),(1);
+mysql> insert into test.t4 values(65, 1),(66, 2), (67, 3), (0, 0);
 mysql> alter table test.t1 set tiflash replica 1;
 mysql> alter table test.t2 set tiflash replica 1;
 mysql> alter table test.t3 set tiflash replica 1;
+mysql> alter table test.t4 set tiflash replica 1;
 
 func> wait_table test t1
 func> wait_table test t2
 func> wait_table test t3
+func> wait_table test t4
 
 mysql> set session tidb_isolation_read_engines='tiflash'; select count(*) from test.t1 where (b between null and 100) is null;
 +----------+
@@ -67,6 +72,18 @@ mysql> set tidb_enforce_mpp=1; set tidb_isolation_read_engines='tiflash'; select
 mysql> set tidb_enforce_mpp=1; set tidb_isolation_read_engines='tiflash'; select count(*) from test.t3 group by a having ifnull(null,count(*)) and min(null);
 # empty
 
+# issue 5849
+mysql> set tidb_enforce_mpp=1; set tidb_isolation_read_engines='tiflash'; select a or b from test.t4;
++--------+
+| a or b |
++--------+
+|      1 |
+|      1 |
+|      1 |
+|      0 |
++--------+
+
 #mysql> drop table if exists test.t1;
 #mysql> drop table if exists test.t2;
 #mysql> drop table if exists test.t3;
+#mysql> drop table if exists test.t4;