fix: autoindex panic with flat index type (#29071) (#29072)

issue: https://github.com/milvus-io/milvus/issues/29048
pr: https://github.com/milvus-io/milvus/pull/29071

---------

Signed-off-by: longjiquan <jiquan.long@zilliz.com>

pkg/util/indexparamcheck/flat_checker.go

@@ -4,6 +4,10 @@ type flatChecker struct {
 	floatVectorBaseChecker
 }
 
+func (c flatChecker) StaticCheck(m map[string]string) error {
+	return c.staticCheck(m)
+}
+
 func newFlatChecker() IndexChecker {
 	return &flatChecker{}
 }

pkg/util/indexparamcheck/flat_checker_test.go

@@ -62,3 +62,40 @@ func Test_flatChecker_CheckTrain(t *testing.T) {
 		}
 	}
 }
+
+func Test_flatChecker_StaticCheck(t *testing.T) {
+	cases := []struct {
+		params   map[string]string
+		errIsNil bool
+	}{
+		{
+			// metrics not found.
+			params:   map[string]string{},
+			errIsNil: false,
+		},
+		{
+			// invalid metric.
+			params: map[string]string{
+				Metric: metric.HAMMING,
+			},
+			errIsNil: false,
+		},
+		{
+			// normal case.
+			params: map[string]string{
+				Metric: metric.L2,
+			},
+			errIsNil: true,
+		},
+	}
+
+	c := newFlatChecker()
+	for _, test := range cases {
+		err := c.StaticCheck(test.params)
+		if test.errIsNil {
+			assert.NoError(t, err)
+		} else {
+			assert.Error(t, err)
+		}
+	}
+}