diff --git a/executor/executor_test.go b/executor/executor_test.go
index 4d1258924bd3a..39067c4064115 100644
--- a/executor/executor_test.go
+++ b/executor/executor_test.go
@@ -6414,3 +6414,14 @@ func (s *testSuite) TestOOMActionPriority(c *C) {
 	}
 	c.Assert(action.GetPriority(), Equals, int64(memory.DefLogPriority))
 }
+
+func (s *testSuite) Test17780(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t0")
+	tk.MustExec("create table t0 (c0 double)")
+	tk.MustExec("insert into t0 values (1e30)")
+	tk.MustExec("update t0 set c0=0 where t0.c0 like 0")
+	// the update should not affect c0
+	tk.MustQuery("select count(*) from t0 where c0 = 0").Check(testkit.Rows("0"))
+}
diff --git a/expression/builtin_cast.go b/expression/builtin_cast.go
index d0b8537b0c115..a7bd79ebaacb9 100644
--- a/expression/builtin_cast.go
+++ b/expression/builtin_cast.go
@@ -1872,6 +1872,10 @@ func WrapWithCastAsString(ctx sessionctx.Context, expr Expression) Expression {
 	if exprTp.EvalType() == types.ETInt {
 		argLen = mysql.MaxIntWidth
 	}
+	// because we can't control the length of cast(float as char) for now, we can't determine the argLen
+	if exprTp.Tp == mysql.TypeFloat || exprTp.Tp == mysql.TypeDouble {
+		argLen = -1
+	}
 	tp := types.NewFieldType(mysql.TypeVarString)
 	tp.Charset, tp.Collate = charset.GetDefaultCharsetAndCollate()
 	tp.Flen, tp.Decimal = argLen, types.UnspecifiedLength
diff --git a/expression/typeinfer_test.go b/expression/typeinfer_test.go
index b1c2be753779b..382e7a4047ebf 100644
--- a/expression/typeinfer_test.go
+++ b/expression/typeinfer_test.go
@@ -279,8 +279,8 @@ func (s *testInferTypeSuite) createTestCase4StrFuncs() []typeInferTestCase {
 		{"elt(c_int_d, c_char, c_char, c_char)", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, 20, types.UnspecifiedLength},
 		{"elt(c_int_d, c_char, c_char, c_binary)", mysql.TypeVarString, charset.CharsetBin, mysql.BinaryFlag, 20, types.UnspecifiedLength},
 		{"elt(c_int_d, c_char, c_int_d)", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, 20, types.UnspecifiedLength},
-		{"elt(c_int_d, c_char, c_double_d, c_int_d)", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, 22, types.UnspecifiedLength},
-		{"elt(c_int_d, c_char, c_double_d, c_int_d, c_binary)", mysql.TypeVarString, charset.CharsetBin, mysql.BinaryFlag, 22, types.UnspecifiedLength},
+		{"elt(c_int_d, c_char, c_double_d, c_int_d)", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, 20, types.UnspecifiedLength},
+		{"elt(c_int_d, c_char, c_double_d, c_int_d, c_binary)", mysql.TypeVarString, charset.CharsetBin, mysql.BinaryFlag, 20, types.UnspecifiedLength},
 
 		{"locate(c_char, c_char)", mysql.TypeLonglong, charset.CharsetBin, mysql.BinaryFlag, mysql.MaxIntWidth, 0},
 		{"locate(c_binary, c_binary)", mysql.TypeLonglong, charset.CharsetBin, mysql.BinaryFlag, mysql.MaxIntWidth, 0},
@@ -405,8 +405,8 @@ func (s *testInferTypeSuite) createTestCase4StrFuncs() []typeInferTestCase {
 
 		{"reverse(c_int_d      )", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, 20, types.UnspecifiedLength},
 		{"reverse(c_bigint_d   )", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, 20, types.UnspecifiedLength},
-		{"reverse(c_float_d    )", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, 12, types.UnspecifiedLength},
-		{"reverse(c_double_d   )", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, 22, types.UnspecifiedLength},
+		{"reverse(c_float_d    )", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, -1, types.UnspecifiedLength},
+		{"reverse(c_double_d   )", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, -1, types.UnspecifiedLength},
 		{"reverse(c_decimal    )", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, 8, types.UnspecifiedLength},
 		{"reverse(c_char       )", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, 20, types.UnspecifiedLength},
 		{"reverse(c_varchar    )", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, 20, types.UnspecifiedLength},
@@ -456,8 +456,8 @@ func (s *testInferTypeSuite) createTestCase4StrFuncs() []typeInferTestCase {
 
 		{"quote(c_int_d      )", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, 42, types.UnspecifiedLength},
 		{"quote(c_bigint_d   )", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, 42, types.UnspecifiedLength},
-		{"quote(c_float_d    )", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, 26, types.UnspecifiedLength},
-		{"quote(c_double_d   )", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, 46, types.UnspecifiedLength},
+		{"quote(c_float_d    )", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, 0, types.UnspecifiedLength},
+		{"quote(c_double_d   )", mysql.TypeVarString, charset.CharsetUTF8MB4, 0, 0, types.UnspecifiedLength},
 
 		{"convert(c_double_d using utf8mb4)", mysql.TypeLongBlob, charset.CharsetUTF8MB4, 0, mysql.MaxBlobWidth, types.UnspecifiedLength},
 		{"convert(c_binary using utf8mb4)", mysql.TypeLongBlob, charset.CharsetUTF8MB4, 0, mysql.MaxBlobWidth, types.UnspecifiedLength},