chore: corrected comment

docs/api/openapi.yml

@@ -4295,6 +4295,10 @@ paths:
         name: metricName
         schema:
           type: string
+      - in: query
+        name: metricNamespace
+        schema:
+          type: string
       - in: query
         name: searchText
         schema:
@@ -4380,6 +4384,10 @@ paths:
         name: metricName
         schema:
           type: string
+      - in: query
+        name: metricNamespace
+        schema:
+          type: string
       - in: query
         name: searchText
         schema:
@@ -8142,6 +8150,10 @@ paths:
         name: metricName
         schema:
           type: string
+      - in: query
+        name: metricNamespace
+        schema:
+          type: string
       - in: query
         name: searchText
         schema:
@@ -8239,6 +8251,10 @@ paths:
         name: metricName
         schema:
           type: string
+      - in: query
+        name: metricNamespace
+        schema:
+          type: string
       - in: query
         name: searchText
         schema:

frontend/src/api/generated/services/sigNoz.schemas.ts

@@ -3723,6 +3723,11 @@ export type GetFieldsKeysParams = {
 	 * @description undefined
 	 */
 	metricName?: string;
+	/**
+	 * @type string
+	 * @description undefined
+	 */
+	metricNamespace?: string;
 	/**
 	 * @type string
 	 * @description undefined
@@ -3777,6 +3782,11 @@ export type GetFieldsValuesParams = {
 	 * @description undefined
 	 */
 	metricName?: string;
+	/**
+	 * @type string
+	 * @description undefined
+	 */
+	metricNamespace?: string;
 	/**
 	 * @type string
 	 * @description undefined
@@ -4456,6 +4466,11 @@ export type GetRuleHistoryFilterKeysParams = {
 	 * @description undefined
 	 */
 	metricName?: string;
+	/**
+	 * @type string
+	 * @description undefined
+	 */
+	metricNamespace?: string;
 	/**
 	 * @type string
 	 * @description undefined
@@ -4513,6 +4528,11 @@ export type GetRuleHistoryFilterValuesParams = {
 	 * @description undefined
 	 */
 	metricName?: string;
+	/**
+	 * @type string
+	 * @description undefined
+	 */
+	metricNamespace?: string;
 	/**
 	 * @type string
 	 * @description undefined

pkg/telemetrymetadata/metadata.go

@@ -651,7 +651,12 @@ func (t *telemetryMetaStore) getMetricsKeys(ctx context.Context, fieldKeySelecto
 		// }
 
 		if fieldKeySelector.MetricContext != nil {
-			fieldConds = append(fieldConds, sb.E("metric_name", fieldKeySelector.MetricContext.MetricName))
+			if fieldKeySelector.MetricContext.MetricName != "" {
+				fieldConds = append(fieldConds, sb.E("metric_name", fieldKeySelector.MetricContext.MetricName))
+			}
+			if fieldKeySelector.MetricContext.MetricNamespace != "" {
+				fieldConds = append(fieldConds, sb.Like("metric_name", escapeForLike(fieldKeySelector.MetricContext.MetricNamespace)+"%"))
+			}
 		}
 
 		conds = append(conds, sb.And(fieldConds...))
@@ -739,7 +744,12 @@ func (t *telemetryMetaStore) getMeterSourceMetricKeys(ctx context.Context, field
 		fieldConds = append(fieldConds, sb.NotLike("attr_name", "\\_\\_%"))
 
 		if fieldKeySelector.MetricContext != nil {
-			fieldConds = append(fieldConds, sb.E("metric_name", fieldKeySelector.MetricContext.MetricName))
+			if fieldKeySelector.MetricContext.MetricName != "" {
+				fieldConds = append(fieldConds, sb.E("metric_name", fieldKeySelector.MetricContext.MetricName))
+			}
+			if fieldKeySelector.MetricContext.MetricNamespace != "" {
+				fieldConds = append(fieldConds, sb.Like("metric_name", escapeForLike(fieldKeySelector.MetricContext.MetricNamespace)+"%"))
+			}
 		}
 
 		conds = append(conds, sb.And(fieldConds...))
@@ -833,8 +843,8 @@ func enrichWithIntrinsicMetricKeys(keys map[string][]*telemetrytypes.TelemetryFi
 		if selector.Signal != telemetrytypes.SignalMetrics && selector.Signal != telemetrytypes.SignalUnspecified {
 			continue
 		}
-		// If a metricName is provided, don’t surface intrinsic metric keys
-		if selector.MetricContext != nil && selector.MetricContext.MetricName != "" {
+		// If metric filters are provided, do not surface intrinsic metric keys.
+		if selector.MetricContext != nil && (selector.MetricContext.MetricName != "" || selector.MetricContext.MetricNamespace != "") {
 			continue
 		}
 
@@ -1383,9 +1393,12 @@ func (t *telemetryMetaStore) getMetricFieldValues(ctx context.Context, fieldValu
 		sb.Where(sb.E("attr_datatype", fieldValueSelector.FieldDataType.TagDataType()))
 	}
 
-	if fieldValueSelector.MetricContext != nil {
+	if fieldValueSelector.MetricContext != nil && fieldValueSelector.MetricContext.MetricName != "" {
 		sb.Where(sb.E("metric_name", fieldValueSelector.MetricContext.MetricName))
 	}
+	if fieldValueSelector.MetricContext != nil && fieldValueSelector.MetricContext.MetricNamespace != "" {
+		sb.Where(sb.Like("metric_name", escapeForLike(fieldValueSelector.MetricContext.MetricNamespace)+"%"))
+	}
 
 	if fieldValueSelector.StartUnixMilli > 0 {
 		sb.Where(sb.GE("last_reported_unix_milli", fieldValueSelector.StartUnixMilli))
@@ -1467,6 +1480,9 @@ func (t *telemetryMetaStore) getIntrinsicMetricFieldValues(ctx context.Context,
 	if fieldValueSelector.MetricContext != nil && fieldValueSelector.MetricContext.MetricName != "" {
 		sb.Where(sb.E("metric_name", fieldValueSelector.MetricContext.MetricName))
 	}
+	if fieldValueSelector.MetricContext != nil && fieldValueSelector.MetricContext.MetricNamespace != "" {
+		sb.Where(sb.Like("metric_name", escapeForLike(fieldValueSelector.MetricContext.MetricNamespace)+"%"))
+	}
 
 	if fieldValueSelector.StartUnixMilli > 0 {
 		sb.Where(sb.GE("unix_milli", fieldValueSelector.StartUnixMilli))
@@ -1524,6 +1540,13 @@ func (t *telemetryMetaStore) getMeterSourceMetricFieldValues(ctx context.Context
 	}
 	sb.Where(sb.NotLike("attr.1", "\\_\\_%"))
 
+	if fieldValueSelector.MetricContext != nil && fieldValueSelector.MetricContext.MetricName != "" {
+		sb.Where(sb.E("metric_name", fieldValueSelector.MetricContext.MetricName))
+	}
+	if fieldValueSelector.MetricContext != nil && fieldValueSelector.MetricContext.MetricNamespace != "" {
+		sb.Where(sb.Like("metric_name", escapeForLike(fieldValueSelector.MetricContext.MetricNamespace)+"%"))
+	}
+
 	if fieldValueSelector.Value != "" {
 		if fieldValueSelector.SelectorMatchType == telemetrytypes.FieldSelectorMatchTypeExact {
 			sb.Where(sb.E("attr.2", fieldValueSelector.Value))

pkg/telemetrymetadata/metadata_test.go

@@ -314,6 +314,20 @@ func TestEnrichWithIntrinsicMetricKeys(t *testing.T) {
 		},
 	)
 	assert.NotContains(t, result, "metric_name")
+
+	result = enrichWithIntrinsicMetricKeys(
+		map[string][]*telemetrytypes.TelemetryFieldKey{},
+		[]*telemetrytypes.FieldKeySelector{
+			{
+				Signal: telemetrytypes.SignalMetrics,
+				MetricContext: &telemetrytypes.MetricContext{
+					MetricNamespace: "system.cpu",
+				},
+				SelectorMatchType: telemetrytypes.FieldSelectorMatchTypeFuzzy,
+			},
+		},
+	)
+	assert.NotContains(t, result, "metric_name")
 }
 
 func TestGetMetricFieldValuesIntrinsicMetricName(t *testing.T) {
@@ -386,3 +400,106 @@ func TestGetMetricFieldValuesIntrinsicBoolReturnsEmpty(t *testing.T) {
 	assert.Empty(t, values.BoolValues)
 	require.NoError(t, mock.ExpectationsWereMet())
 }
+
+func TestGetMetricFieldValuesAppliesMetricNamespace(t *testing.T) {
+	mockTelemetryStore := telemetrystoretest.New(telemetrystore.Config{}, &regexMatcher{})
+	mock := mockTelemetryStore.Mock()
+
+	metadata := newTestTelemetryMetaStoreTestHelper(mockTelemetryStore)
+
+	valueRows := cmock.NewRows([]cmock.ColumnType{
+		{Name: "attr_string_value", Type: "String"},
+	}, [][]any{{"value.a"}})
+
+	mock.ExpectQuery(regexp.QuoteMeta("SELECT DISTINCT attr_string_value FROM signoz_metrics.distributed_metadata WHERE attr_name = ? AND metric_name LIKE ? LIMIT ?")).
+		WithArgs("custom_key", "system.cpu%", 11).
+		WillReturnRows(valueRows)
+
+	values, complete, err := metadata.(*telemetryMetaStore).getMetricFieldValues(context.Background(), &telemetrytypes.FieldValueSelector{
+		FieldKeySelector: &telemetrytypes.FieldKeySelector{
+			Signal:            telemetrytypes.SignalMetrics,
+			Name:              "custom_key",
+			Limit:             10,
+			SelectorMatchType: telemetrytypes.FieldSelectorMatchTypeFuzzy,
+			MetricContext: &telemetrytypes.MetricContext{
+				MetricNamespace: "system.cpu",
+			},
+		},
+		Limit: 10,
+	})
+	require.NoError(t, err)
+	assert.True(t, complete)
+	assert.ElementsMatch(t, []string{"value.a"}, values.StringValues)
+	require.NoError(t, mock.ExpectationsWereMet())
+}
+
+func TestGetMetricFieldValuesIntrinsicMetricNameAppliesMetricNamespace(t *testing.T) {
+	mockTelemetryStore := telemetrystoretest.New(telemetrystore.Config{}, &regexMatcher{})
+	mock := mockTelemetryStore.Mock()
+
+	metadata := newTestTelemetryMetaStoreTestHelper(mockTelemetryStore)
+
+	valueRows := cmock.NewRows([]cmock.ColumnType{
+		{Name: "metric_name", Type: "String"},
+	}, [][]any{{"system.cpu.utilization"}})
+
+	mock.ExpectQuery(regexp.QuoteMeta("SELECT metric_name FROM signoz_metrics.distributed_time_series_v4_1week WHERE metric_name LIKE ? GROUP BY metric_name LIMIT ?")).
+		WithArgs("system.cpu%", 51).
+		WillReturnRows(valueRows)
+
+	metadataRows := cmock.NewRows([]cmock.ColumnType{
+		{Name: "attr_string_value", Type: "String"},
+	}, [][]any{})
+
+	mock.ExpectQuery(regexp.QuoteMeta("SELECT DISTINCT attr_string_value FROM signoz_metrics.distributed_metadata WHERE attr_name = ? AND metric_name LIKE ? LIMIT ?")).
+		WithArgs("metric_name", "system.cpu%", 50).
+		WillReturnRows(metadataRows)
+
+	values, complete, err := metadata.(*telemetryMetaStore).getMetricFieldValues(context.Background(), &telemetrytypes.FieldValueSelector{
+		FieldKeySelector: &telemetrytypes.FieldKeySelector{
+			Signal:            telemetrytypes.SignalMetrics,
+			Name:              "metric_name",
+			Limit:             50,
+			SelectorMatchType: telemetrytypes.FieldSelectorMatchTypeFuzzy,
+			MetricContext: &telemetrytypes.MetricContext{
+				MetricNamespace: "system.cpu",
+			},
+		},
+		Limit: 50,
+	})
+	require.NoError(t, err)
+	assert.True(t, complete)
+	assert.ElementsMatch(t, []string{"system.cpu.utilization"}, values.StringValues)
+	require.NoError(t, mock.ExpectationsWereMet())
+}
+
+func TestGetMeterSourceMetricFieldValuesAppliesMetricNamespace(t *testing.T) {
+	mockTelemetryStore := telemetrystoretest.New(telemetrystore.Config{}, &regexMatcher{})
+	mock := mockTelemetryStore.Mock()
+
+	metadata := newTestTelemetryMetaStoreTestHelper(mockTelemetryStore)
+
+	rows := cmock.NewRows([]cmock.ColumnType{
+		{Name: "attr", Type: "Array(String)"},
+	}, [][]any{{[]string{"service.name", "frontend"}}})
+
+	mock.ExpectQuery(`SELECT .*distributed_samples_agg_1d.*metric_name LIKE .*`).
+		WithArgs("service.name", "\\_\\_%", "system.cpu%", "", 11).
+		WillReturnRows(rows)
+
+	values, complete, err := metadata.(*telemetryMetaStore).getMeterSourceMetricFieldValues(context.Background(), &telemetrytypes.FieldValueSelector{
+		FieldKeySelector: &telemetrytypes.FieldKeySelector{
+			Signal: telemetrytypes.SignalMetrics,
+			Source: telemetrytypes.SourceMeter,
+			Name:   "service.name",
+			MetricContext: &telemetrytypes.MetricContext{
+				MetricNamespace: "system.cpu",
+			},
+		},
+		Limit: 10,
+	})
+	require.NoError(t, err)
+	assert.True(t, complete)
+	assert.ElementsMatch(t, []string{"frontend"}, values.StringValues)
+	require.NoError(t, mock.ExpectationsWereMet())
+}

pkg/types/telemetrytypes/field.go

@@ -268,7 +268,8 @@ func (t *TelemetryFieldValues) NumValues() int {
 }
 
 type MetricContext struct {
-	MetricName string `json:"metricName"`
+	MetricName      string `json:"metricName"`
+	MetricNamespace string `json:"metricNamespace,omitempty"`
 }
 
 type FieldKeySelector struct {
@@ -297,15 +298,16 @@ type GettableFieldKeys struct {
 }
 
 type PostableFieldKeysParams struct {
-	Signal         Signal        `query:"signal"`
-	Source         Source        `query:"source"`
-	Limit          int           `query:"limit"`
-	StartUnixMilli int64         `query:"startUnixMilli"`
-	EndUnixMilli   int64         `query:"endUnixMilli"`
-	FieldContext   FieldContext  `query:"fieldContext"`
-	FieldDataType  FieldDataType `query:"fieldDataType"`
-	MetricName     string        `query:"metricName"`
-	SearchText     string        `query:"searchText"`
+	Signal          Signal        `query:"signal"`
+	Source          Source        `query:"source"`
+	Limit           int           `query:"limit"`
+	StartUnixMilli  int64         `query:"startUnixMilli"`
+	EndUnixMilli    int64         `query:"endUnixMilli"`
+	FieldContext    FieldContext  `query:"fieldContext"`
+	FieldDataType   FieldDataType `query:"fieldDataType"`
+	MetricName      string        `query:"metricName"`
+	MetricNamespace string        `query:"metricNamespace"`
+	SearchText      string        `query:"searchText"`
 }
 
 type GettableFieldValues struct {
@@ -344,9 +346,10 @@ func NewFieldKeySelectorFromPostableFieldKeysParams(params PostableFieldKeysPara
 		req.Limit = 1000
 	}
 
-	if params.MetricName != "" {
+	if params.MetricName != "" || params.MetricNamespace != "" {
 		req.MetricContext = &MetricContext{
-			MetricName: params.MetricName,
+			MetricName:      params.MetricName,
+			MetricNamespace: params.MetricNamespace,
 		}
 	}
 

pkg/types/telemetrytypes/field_test.go

@@ -394,3 +394,20 @@ func TestNormalize(t *testing.T) {
 		})
 	}
 }
+
+func TestNewFieldKeySelectorFromPostableFieldKeysParamsMetricNamespace(t *testing.T) {
+	selector := NewFieldKeySelectorFromPostableFieldKeysParams(PostableFieldKeysParams{
+		Signal:          SignalMetrics,
+		MetricNamespace: "system.cpu",
+	})
+
+	if selector.MetricContext == nil {
+		t.Fatalf("expected metric context to be set")
+	}
+	if selector.MetricContext.MetricNamespace != "system.cpu" {
+		t.Fatalf("expected metric namespace to be propagated, got %q", selector.MetricContext.MetricNamespace)
+	}
+	if selector.MetricContext.MetricName != "" {
+		t.Fatalf("expected metric name to remain empty, got %q", selector.MetricContext.MetricName)
+	}
+}

tests/integration/src/querier/03_metrics.py

@@ -658,3 +658,211 @@ def test_non_existent_metrics_returns_404(
         get_error_message(response.json())
         == "could not find the metric whatevergoennnsgoeshere"
     )
+
+
+# Verify /api/v1/fields/values filters label values by metricNamespace prefix.
+# Inserts metrics under ns.a and ns.b, then asserts a specific prefix returns
+# only matching values while a common prefix returns both.
+def test_metric_namespace_values_filtering(
+    signoz: types.SigNoz,
+    create_user_admin: None,  # pylint: disable=unused-argument
+    get_token: Callable[[str, str], str],
+    insert_metrics: Callable[[List[Metrics]], None],
+) -> None:
+    now = datetime.now(tz=timezone.utc).replace(second=0, microsecond=0)
+
+    metrics: List[Metrics] = [
+        Metrics(
+            metric_name="ns.a.requests_total",
+            labels={"service": "svc-a"},
+            timestamp=now - timedelta(minutes=2),
+            value=10.0,
+        ),
+        Metrics(
+            metric_name="ns.b.requests_total",
+            labels={"service": "svc-b"},
+            timestamp=now - timedelta(minutes=2),
+            value=20.0,
+        ),
+    ]
+    insert_metrics(metrics)
+
+    token = get_token(USER_ADMIN_EMAIL, USER_ADMIN_PASSWORD)
+
+    # Specific prefix: metricNamespace=ns.a should return only svc-a
+    response = requests.get(
+        signoz.self.host_configs["8080"].get("/api/v1/fields/values"),
+        timeout=5,
+        headers={"authorization": f"Bearer {token}"},
+        params={
+            "signal": "metrics",
+            "name": "service",
+            "searchText": "",
+            "metricNamespace": "ns.a",
+        },
+    )
+
+    assert response.status_code == HTTPStatus.OK
+    assert response.json()["status"] == "success"
+
+    values = response.json()["data"]["values"]["stringValues"]
+    assert "svc-a" in values
+    assert "svc-b" not in values
+
+    # Common prefix: metricNamespace=ns should return both
+    response = requests.get(
+        signoz.self.host_configs["8080"].get("/api/v1/fields/values"),
+        timeout=5,
+        headers={"authorization": f"Bearer {token}"},
+        params={
+            "signal": "metrics",
+            "name": "service",
+            "searchText": "",
+            "metricNamespace": "ns",
+        },
+    )
+
+    assert response.status_code == HTTPStatus.OK
+    assert response.json()["status"] == "success"
+
+    values = response.json()["data"]["values"]["stringValues"]
+    assert "svc-a" in values
+    assert "svc-b" in values
+
+
+# Verify /api/v1/fields/values with name=metric_name filters metric names by
+# metricNamespace prefix. A specific prefix returns only its metric names;
+# a common prefix returns metric names from all matching namespaces.
+def test_metric_namespace_metric_name_values_filtering(
+    signoz: types.SigNoz,
+    create_user_admin: None,  # pylint: disable=unused-argument
+    get_token: Callable[[str, str], str],
+    insert_metrics: Callable[[List[Metrics]], None],
+) -> None:
+    now = datetime.now(tz=timezone.utc).replace(second=0, microsecond=0)
+
+    metrics: List[Metrics] = [
+        Metrics(
+            metric_name="ns.a.cpu.utilization",
+            labels={"host": "host-a"},
+            timestamp=now - timedelta(minutes=2),
+            value=50.0,
+        ),
+        Metrics(
+            metric_name="ns.b.cpu.utilization",
+            labels={"host": "host-b"},
+            timestamp=now - timedelta(minutes=2),
+            value=60.0,
+        ),
+    ]
+    insert_metrics(metrics)
+
+    token = get_token(USER_ADMIN_EMAIL, USER_ADMIN_PASSWORD)
+
+    # Specific prefix: metricNamespace=ns.a should return only ns.a.* metric names
+    response = requests.get(
+        signoz.self.host_configs["8080"].get("/api/v1/fields/values"),
+        timeout=5,
+        headers={"authorization": f"Bearer {token}"},
+        params={
+            "signal": "metrics",
+            "name": "metric_name",
+            "searchText": "",
+            "metricNamespace": "ns.a",
+        },
+    )
+
+    assert response.status_code == HTTPStatus.OK
+    assert response.json()["status"] == "success"
+
+    values = response.json()["data"]["values"]["stringValues"]
+    assert "ns.a.cpu.utilization" in values
+    assert "ns.b.cpu.utilization" not in values
+
+    # Common prefix: metricNamespace=ns should return both
+    response = requests.get(
+        signoz.self.host_configs["8080"].get("/api/v1/fields/values"),
+        timeout=5,
+        headers={"authorization": f"Bearer {token}"},
+        params={
+            "signal": "metrics",
+            "name": "metric_name",
+            "searchText": "",
+            "metricNamespace": "ns",
+        },
+    )
+
+    assert response.status_code == HTTPStatus.OK
+    assert response.json()["status"] == "success"
+
+    values = response.json()["data"]["values"]["stringValues"]
+    assert "ns.a.cpu.utilization" in values
+    assert "ns.b.cpu.utilization" in values
+
+
+# Verify /api/v1/fields/keys filters attribute keys by metricNamespace prefix.
+# Metrics under ns.a and ns.b carry distinct labels; a specific prefix returns
+# only its keys while a common prefix returns keys from both namespaces.
+def test_metric_namespace_keys_filtering(
+    signoz: types.SigNoz,
+    create_user_admin: None,  # pylint: disable=unused-argument
+    get_token: Callable[[str, str], str],
+    insert_metrics: Callable[[List[Metrics]], None],
+) -> None:
+    now = datetime.now(tz=timezone.utc).replace(second=0, microsecond=0)
+
+    metrics: List[Metrics] = [
+        Metrics(
+            metric_name="ns.a.cpu.utilization",
+            labels={"a_only_label": "val-a"},
+            timestamp=now - timedelta(minutes=2),
+            value=10.0,
+        ),
+        Metrics(
+            metric_name="ns.b.cpu.utilization",
+            labels={"b_only_label": "val-b"},
+            timestamp=now - timedelta(minutes=2),
+            value=20.0,
+        ),
+    ]
+    insert_metrics(metrics)
+
+    token = get_token(USER_ADMIN_EMAIL, USER_ADMIN_PASSWORD)
+
+    # Specific prefix: metricNamespace=ns.a should return only a_only_label
+    response = requests.get(
+        signoz.self.host_configs["8080"].get("/api/v1/fields/keys"),
+        timeout=5,
+        headers={"authorization": f"Bearer {token}"},
+        params={
+            "signal": "metrics",
+            "searchText": "label",
+            "metricNamespace": "ns.a",
+        },
+    )
+
+    assert response.status_code == HTTPStatus.OK
+    assert response.json()["status"] == "success"
+
+    keys = response.json()["data"]["keys"]
+    assert "a_only_label" in keys
+    assert "b_only_label" not in keys
+
+    # Common prefix: metricNamespace=ns should return both keys
+    response = requests.get(
+        signoz.self.host_configs["8080"].get("/api/v1/fields/keys"),
+        timeout=5,
+        headers={"authorization": f"Bearer {token}"},
+        params={
+            "signal": "metrics",
+            "searchText": "label",
+            "metricNamespace": "ns",
+        },
+    )
+
+    assert response.status_code == HTTPStatus.OK
+    assert response.json()["status"] == "success"
+
+    keys = response.json()["data"]["keys"]
+    assert "a_only_label" in keys
+    assert "b_only_label" in keys

tests/integration/src/querier/11_cost_meter.py

@@ -108,3 +108,81 @@ def test_list_meter_metric_names(
     assert (
         metric_name in metric_names
     ), f"Expected {metric_name} in metric names, got: {metric_names}"
+
+
+# Verify /api/v1/fields/values with source=meter filters label values by metricNamespace
+# prefix. Inserts meter-source metrics under ns.a and ns.b, then asserts a specific
+# prefix returns only matching values while a common prefix returns both.
+def test_metric_namespace_meter_values_filtering(
+    signoz: types.SigNoz,
+    create_user_admin: None,  # pylint: disable=unused-argument
+    get_token: Callable[[str, str], str],
+    insert_meter_samples: Callable[[List[MeterSample]], None],
+) -> None:
+    now = datetime.now(tz=timezone.utc).replace(second=0, microsecond=0)
+
+    samples_a = make_meter_samples(
+        "meter.ns.a.cost",
+        {"service": "billing-a"},
+        now,
+        count=5,
+        base_value=10.0,
+        temporality="Delta",
+        type_="Sum",
+        is_monotonic=True,
+    )
+    samples_b = make_meter_samples(
+        "meter.ns.b.cost",
+        {"service": "billing-b"},
+        now,
+        count=5,
+        base_value=20.0,
+        temporality="Delta",
+        type_="Sum",
+        is_monotonic=True,
+    )
+    insert_meter_samples(samples_a + samples_b)
+
+    token = get_token(USER_ADMIN_EMAIL, USER_ADMIN_PASSWORD)
+
+    # Specific prefix: metricNamespace=meter.ns.a should return only billing-a
+    response = requests.get(
+        signoz.self.host_configs["8080"].get("/api/v1/fields/values"),
+        timeout=5,
+        headers={"authorization": f"Bearer {token}"},
+        params={
+            "signal": "metrics",
+            "source": "meter",
+            "name": "service",
+            "searchText": "",
+            "metricNamespace": "meter.ns.a",
+        },
+    )
+
+    assert response.status_code == HTTPStatus.OK
+    assert response.json()["status"] == "success"
+
+    values = response.json()["data"]["values"]["stringValues"]
+    assert "billing-a" in values
+    assert "billing-b" not in values
+
+    # Common prefix: metricNamespace=meter.ns should return both
+    response = requests.get(
+        signoz.self.host_configs["8080"].get("/api/v1/fields/values"),
+        timeout=5,
+        headers={"authorization": f"Bearer {token}"},
+        params={
+            "signal": "metrics",
+            "source": "meter",
+            "name": "service",
+            "searchText": "",
+            "metricNamespace": "meter.ns",
+        },
+    )
+
+    assert response.status_code == HTTPStatus.OK
+    assert response.json()["status"] == "success"
+
+    values = response.json()["data"]["values"]["stringValues"]
+    assert "billing-a" in values
+    assert "billing-b" in values