From e2f19311dce2a47cd17b53950edcf43af719fb9d Mon Sep 17 00:00:00 2001
From: Kuba Kaflik <kuba.kaflik@clickhouse.com>
Date: Wed, 11 Oct 2023 08:06:46 +0200
Subject: [PATCH 1/2] Fix an empty JSON map append using _dummy column

---
 lib/column/json.go        | 10 +++++++++
 tests/issues/1113_test.go | 43 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 53 insertions(+)
 create mode 100644 tests/issues/1113_test.go

diff --git a/lib/column/json.go b/lib/column/json.go
index ca9120668e..aa1fa9dd6a 100644
--- a/lib/column/json.go
+++ b/lib/column/json.go
@@ -501,6 +501,16 @@ func appendStructOrMap(jCol *JSONObject, data any) error {
 				Err:        fmt.Errorf("map keys must be string for column %s", jCol.Name()),
 			}
 		}
+
+		if vData.Len() == 0 {
+			// if map is empty, we need to create a dummy map to make ClickHouse Tuple happy
+			// this is exactly what ClickHouse does when it receives an empty `{}` object string
+			// JSON representation will become '{"_dummy":0}'
+			// JSON object type is experimental and may change in the future
+			vData = reflect.MakeMap(reflect.MapOf(reflect.TypeOf("_dummy"), reflect.TypeOf(uint8(0))))
+			vData.SetMapIndex(reflect.ValueOf("_dummy"), reflect.ValueOf(uint8(0)))
+		}
+
 		return iterateMap(vData, jCol, 0)
 	}
 	return &UnsupportedColumnTypeError{
diff --git a/tests/issues/1113_test.go b/tests/issues/1113_test.go
new file mode 100644
index 0000000000..da9e6293f3
--- /dev/null
+++ b/tests/issues/1113_test.go
@@ -0,0 +1,43 @@
+package issues
+
+import (
+	"context"
+	"github.com/ClickHouse/clickhouse-go/v2"
+	clickhouse_tests "github.com/ClickHouse/clickhouse-go/v2/tests"
+	"github.com/stretchr/testify/require"
+	"testing"
+)
+
+func Test1113(t *testing.T) {
+	var (
+		conn, err = clickhouse_tests.GetConnection("issues", clickhouse.Settings{
+			"max_execution_time":             60,
+			"allow_experimental_object_type": true,
+		}, nil, &clickhouse.Compression{
+			Method: clickhouse.CompressionLZ4,
+		})
+	)
+	ctx := context.Background()
+	require.NoError(t, err)
+	const ddl = `
+		CREATE TABLE test_1113 (
+			col_1 JSON,
+			col_2 JSON
+		) Engine MergeTree() ORDER BY tuple()
+		`
+	require.NoError(t, conn.Exec(ctx, ddl))
+	defer func() {
+		conn.Exec(ctx, "DROP TABLE IF EXISTS test_1113")
+	}()
+
+	batch, err := conn.PrepareBatch(context.Background(), "INSERT INTO test_1113")
+	require.NoError(t, err)
+
+	v1 := map[string]struct {
+		Str string
+	}{"a": {Str: "value"}}
+	v2 := map[string]any{}
+
+	require.NoError(t, batch.Append(v1, v2))
+	require.NoError(t, batch.Send())
+}

From 6bdd7afcf639047d9943660a573e8319959b809c Mon Sep 17 00:00:00 2001
From: Kuba Kaflik <kuba.kaflik@clickhouse.com>
Date: Wed, 11 Oct 2023 09:51:44 +0200
Subject: [PATCH 2/2] Fix an empty JSON map append using _dummy column

---
 lib/column/json.go        | 17 +++++++++++------
 tests/issues/1113_test.go |  7 +------
 2 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/lib/column/json.go b/lib/column/json.go
index aa1fa9dd6a..1c11c3b1bd 100644
--- a/lib/column/json.go
+++ b/lib/column/json.go
@@ -503,12 +503,17 @@ func appendStructOrMap(jCol *JSONObject, data any) error {
 		}
 
 		if vData.Len() == 0 {
-			// if map is empty, we need to create a dummy map to make ClickHouse Tuple happy
-			// this is exactly what ClickHouse does when it receives an empty `{}` object string
-			// JSON representation will become '{"_dummy":0}'
-			// JSON object type is experimental and may change in the future
-			vData = reflect.MakeMap(reflect.MapOf(reflect.TypeOf("_dummy"), reflect.TypeOf(uint8(0))))
-			vData.SetMapIndex(reflect.ValueOf("_dummy"), reflect.ValueOf(uint8(0)))
+			// if map is empty, we need to create an empty Tuple to make sure subcolumns protocol is happy
+			// _dummy is a ClickHouse internal name for empty Tuple subcolumn
+			// it has the same effect as `INSERT INTO single_json_type_table VALUES ('{}');`
+			emptyVal := &JSONValue{Interface: &UInt8{name: "_dummy"}}
+			if err := emptyVal.appendEmptyValue(); err != nil {
+				return err
+			}
+			jCol.columns = []JSON{
+				emptyVal,
+			}
+			return nil
 		}
 
 		return iterateMap(vData, jCol, 0)
diff --git a/tests/issues/1113_test.go b/tests/issues/1113_test.go
index da9e6293f3..2de26ccfee 100644
--- a/tests/issues/1113_test.go
+++ b/tests/issues/1113_test.go
@@ -19,12 +19,7 @@ func Test1113(t *testing.T) {
 	)
 	ctx := context.Background()
 	require.NoError(t, err)
-	const ddl = `
-		CREATE TABLE test_1113 (
-			col_1 JSON,
-			col_2 JSON
-		) Engine MergeTree() ORDER BY tuple()
-		`
+	const ddl = "CREATE TABLE test_1113 (col_1 JSON, col_2 JSON) Engine MergeTree() ORDER BY tuple()"
 	require.NoError(t, conn.Exec(ctx, ddl))
 	defer func() {
 		conn.Exec(ctx, "DROP TABLE IF EXISTS test_1113")