expression: fix wrong result when convert float to unsigned (#53590)

expression/builtin_compare.go

@@ -1481,6 +1481,12 @@ func RefineComparedConstant(ctx sessionctx.Context, targetFieldType types.FieldT
 		targetFieldType = *types.NewFieldType(mysql.TypeLonglong)
 	}
 	var intDatum types.Datum
+	// To make sure return zero when underflow happens.
+	oriFlag := sc.IsRefineComparedConstant
+	sc.IsRefineComparedConstant = true
+	defer func() {
+		sc.IsRefineComparedConstant = oriFlag
+	}()
 	intDatum, err = dt.ConvertTo(sc, &targetFieldType)
 	if err != nil {
 		if terror.ErrorEqual(err, types.ErrOverflow) {

sessionctx/stmtctx/stmtctx.go

@@ -132,6 +132,9 @@ type StatementContext struct {
 	SkipUTF8Check          bool
 	SkipASCIICheck         bool
 	SkipUTF8MB4Check       bool
+
+	IsRefineComparedConstant bool
+
 	// If the select statement was like 'select * from t as of timestamp ...' or in a stale read transaction
 	// or is affected by the tidb_read_staleness session variable, then the statement will be makred as isStaleness
 	// in stmtCtx
@@ -775,7 +778,7 @@ func (sc *StatementContext) GetExecDetails() execdetails.ExecDetails {
 // This is the case for `insert`, `update`, `alter table`, `create table` and `load data infile` statements, when not in strict SQL mode.
 // see https://dev.mysql.com/doc/refman/5.7/en/out-of-range-and-overflow.html
 func (sc *StatementContext) ShouldClipToZero() bool {
-	return sc.InInsertStmt || sc.InLoadDataStmt || sc.InUpdateStmt || sc.InCreateOrAlterStmt || sc.IsDDLJobInQueue
+	return sc.InInsertStmt || sc.InLoadDataStmt || sc.InUpdateStmt || sc.InCreateOrAlterStmt || sc.IsDDLJobInQueue || sc.IsRefineComparedConstant
 }
 
 // ShouldIgnoreOverflowError indicates whether we should ignore the error when type conversion overflows,

tests/integrationtest/r/expression/cast.result

@@ -0,0 +1,30 @@
+drop table if exists t0;
+create table t0(c0 tinyint(1) unsigned not null );
+insert into t0 values (1);
+select * from t0 where case 0 when t0.c0 > -1.194192591e9 then null else 1 end;
+c0
+1
+select t0.c0 > -1.194192591e9 from t0;
+t0.c0 > -1.194192591e9
+1
+select t0.c0 < -1.194192591e9 from t0;
+t0.c0 < -1.194192591e9
+0
+select -1.194192591e9 > t0.c0 from t0;
+-1.194192591e9 > t0.c0
+0
+select -1.194192591e9 < t0.c0 from t0;
+-1.194192591e9 < t0.c0
+1
+select t0.c0 > 1.194192591e9 from t0;
+t0.c0 > 1.194192591e9
+0
+select t0.c0 < 1.194192591e9 from t0;
+t0.c0 < 1.194192591e9
+1
+select 1.194192591e9 > t0.c0 from t0;
+1.194192591e9 > t0.c0
+1
+select 1.194192591e9 < t0.c0 from t0;
+1.194192591e9 < t0.c0
+0

tests/integrationtest/t/expression/cast.test

@@ -0,0 +1,13 @@
+# TestNegFloatConvertToUnsigned
+drop table if exists t0;
+create table t0(c0 tinyint(1) unsigned not null );
+insert into t0 values (1);
+select * from t0 where case 0 when t0.c0 > -1.194192591e9 then null else 1 end;
+select t0.c0 > -1.194192591e9 from t0;
+select t0.c0 < -1.194192591e9 from t0;
+select -1.194192591e9 > t0.c0 from t0;
+select -1.194192591e9 < t0.c0 from t0;
+select t0.c0 > 1.194192591e9 from t0;
+select t0.c0 < 1.194192591e9 from t0;
+select 1.194192591e9 > t0.c0 from t0;
+select 1.194192591e9 < t0.c0 from t0;