feat(go): batch tdengine history writes

go/vehicle-gateway/internal/history/writer_test.go

@@ -226,6 +226,53 @@ func TestWriterSkipsLocationWhenVINIsMissing(t *testing.T) {
 	}
 }
 
+func TestWriterAppendsBatchRowsByChildTable(t *testing.T) {
+	exec := &recordingExec{}
+	writer := NewWriter(exec)
+	first := sampleEnvelope()
+	second := sampleEnvelope()
+	second.Sequence = 2
+	second.EventTimeMS += 1000
+	second.ReceivedAtMS += 1000
+
+	if err := writer.AppendAllBatch(context.Background(), []envelope.FrameEnvelope{first, second}); err != nil {
+		t.Fatalf("AppendAllBatch() error = %v", err)
+	}
+
+	if got := countSQL(exec.calls, "USING raw_frames"); got != 1 {
+		t.Fatalf("raw child create count = %d", got)
+	}
+	if got := countSQL(exec.calls, "USING vehicle_locations"); got != 1 {
+		t.Fatalf("location child create count = %d", got)
+	}
+	if got := countSQL(exec.calls, "INSERT INTO raw_"); got != 1 {
+		t.Fatalf("raw batch insert count = %d", got)
+	}
+	if got := countSQL(exec.calls, "INSERT INTO loc_"); got != 1 {
+		t.Fatalf("location batch insert count = %d", got)
+	}
+	rawInsert := findSQL(exec.calls, "INSERT INTO raw_")
+	if got := strings.Count(rawInsert, "),(") + 1; got != 2 {
+		t.Fatalf("raw batch row count = %d, sql=%s", got, rawInsert)
+	}
+	locationInsert := findSQL(exec.calls, "INSERT INTO loc_")
+	if got := strings.Count(locationInsert, "),(") + 1; got != 2 {
+		t.Fatalf("location batch row count = %d, sql=%s", got, locationInsert)
+	}
+}
+
+func TestWriterAppendAllBatchSkipsEmptyBatch(t *testing.T) {
+	exec := &recordingExec{}
+	writer := NewWriter(exec)
+
+	if err := writer.AppendAllBatch(context.Background(), nil); err != nil {
+		t.Fatalf("AppendAllBatch() error = %v", err)
+	}
+	if len(exec.calls) != 0 {
+		t.Fatalf("exec calls = %#v, want none", exec.calls)
+	}
+}
+
 func TestRawSizeBytesUsesRawTextWhenHexIsEmpty(t *testing.T) {
 	env := envelope.FrameEnvelope{RawText: `{"code":"0F80","data":{"speed":12}}`}
 	if got, want := rawSizeBytes(env), len([]byte(env.RawText)); got != want {