apache · eldenmoon · May 8, 2026
diff --git a/be/src/common/config.cpp b/be/src/common/config.cpp
@@ -1164,6 +1164,7 @@ DEFINE_mBool(variant_use_cloud_schema_dict_cache, "true");
 DEFINE_mInt64(variant_threshold_rows_to_estimate_sparse_column, "2048");
 DEFINE_mInt32(variant_max_json_key_length, "255");
 DEFINE_mBool(variant_throw_exeception_on_invalid_json, "false");
+DEFINE_mBool(variant_enable_duplicate_json_path_check, "false");
 DEFINE_mBool(enable_vertical_compact_variant_subcolumns, "true");
 DEFINE_mBool(enable_variant_doc_sparse_write_subcolumns, "true");
 // Maximum depth of nested arrays to track with NestedGroup

diff --git a/be/src/common/config.h b/be/src/common/config.h
@@ -1425,6 +1425,8 @@ DECLARE_mInt64(variant_threshold_rows_to_estimate_sparse_column);
 DECLARE_mInt32(variant_max_json_key_length);
 // Treat invalid json format str as string, instead of throwing exception if false
 DECLARE_mBool(variant_throw_exeception_on_invalid_json);
+// Enable duplicate path check when parsing json into variant subcolumns/jsonb.
+DECLARE_mBool(variant_enable_duplicate_json_path_check);
 // Enable vertical compact subcolumns of variant column
 DECLARE_mBool(enable_vertical_compact_variant_subcolumns);
 DECLARE_mBool(enable_variant_doc_sparse_write_subcolumns);

diff --git a/be/src/core/data_type_serde/data_type_variant_serde.cpp b/be/src/core/data_type_serde/data_type_variant_serde.cpp
@@ -21,6 +21,7 @@
 #include <string>
 
 #include "common/cast_set.h"
+#include "common/config.h"
 #include "common/exception.h"
 #include "common/status.h"
 #include "core/assert_cast.h"
@@ -107,10 +108,11 @@ Status DataTypeVariantSerDe::serialize_one_cell_to_json(const IColumn& column, i
 
 Status DataTypeVariantSerDe::deserialize_one_cell_from_json(IColumn& column, Slice& slice,
                                                             const FormatOptions& options) const {
-    ParseConfig config;
+    ParseConfig parse_config;
+    parse_config.check_duplicate_json_path = config::variant_enable_duplicate_json_path_check;
     StringRef json_ref(slice.data, slice.size);
     RETURN_IF_CATCH_EXCEPTION(
-            variant_util::parse_json_to_variant(column, json_ref, nullptr, config));
+            variant_util::parse_json_to_variant(column, json_ref, nullptr, parse_config));
     return Status::OK();
 }
 

diff --git a/be/src/exec/common/variant_util.cpp b/be/src/exec/common/variant_util.cpp
@@ -2016,36 +2016,64 @@ void parse_json_to_variant_impl(IColumn& column, const char* src, size_t length,
         }
     };
 
+    auto is_plain_path = [](const PathInData& path) {
+        for (const auto& part : path.get_parts()) {
+            if (part.is_nested || part.anonymous_array_level != 0) {
+                return false;
+            }
+        }
+        return true;
+    };
+
     auto get_or_create_subcolumn = [&](const PathInData& path, size_t index_hint,
                                        const FieldInfo& field_info) -> ColumnVariant::Subcolumn* {
-        if (column_variant.get_subcolumn(path, index_hint) == nullptr) {
+        auto* subcolumn = column_variant.get_subcolumn(path, index_hint);
+        if (subcolumn == nullptr && !path.empty() && config.check_duplicate_json_path &&
+            is_plain_path(path)) {
+            const auto& path_name = path.get_path();
+            for (auto& entry : column_variant.get_subcolumns()) {
+                if (entry->path.get_path() == path_name && is_plain_path(entry->path)) {
+                    subcolumn = &entry->data;
+                    break;
+                }
+            }
+        }
+        if (subcolumn == nullptr) {
             if (path.has_nested_part()) {
                 column_variant.add_nested_subcolumn(path, field_info, old_num_rows);
             } else {
                 column_variant.add_sub_column(path, old_num_rows);
             }
+            subcolumn = column_variant.get_subcolumn(path, index_hint);
         }
-        auto* subcolumn = column_variant.get_subcolumn(path, index_hint);
         if (!subcolumn) {
             throw doris::Exception(ErrorCode::INVALID_ARGUMENT, "Failed to find sub column {}",
                                    path.get_path());
         }
         return subcolumn;
     };
 
+    auto normalize_plain_path = [&](const PathInData& path) {
+        if (!config.check_duplicate_json_path || path.empty() || !is_plain_path(path)) {
+            return path;
+        }
+        return PathInData(path.get_path());
+    };
+
     auto insert_into_subcolumn = [&](size_t i,
                                      bool check_size_mismatch) -> ColumnVariant::Subcolumn* {
         FieldInfo field_info;
         get_field_info(values[i], &field_info);
         if (field_info.scalar_type_id == PrimitiveType::INVALID_TYPE) {
             return nullptr;
         }
-        auto* subcolumn = get_or_create_subcolumn(paths[i], i, field_info);
+        auto path = normalize_plain_path(paths[i]);
+        auto* subcolumn = get_or_create_subcolumn(path, i, field_info);
         flush_defaults(subcolumn);
         if (check_size_mismatch && subcolumn->size() != old_num_rows) {
             throw doris::Exception(ErrorCode::INVALID_ARGUMENT,
                                    "subcolumn {} size missmatched, may contains duplicated entry",
-                                   paths[i].get_path());
+                                   path.get_path());
         }
         subcolumn->insert(std::move(values[i]), std::move(field_info));
         return subcolumn;
@@ -2309,6 +2337,7 @@ Status parse_and_materialize_variant_columns(Block& block, const TabletSchema& t
         // Deprecated legacy flatten-nested switch. Distinct from variant_enable_nested_group.
         configs[i].deprecated_enable_flatten_nested =
                 tablet_schema.deprecated_variant_flatten_nested();
+        configs[i].check_duplicate_json_path = config::variant_enable_duplicate_json_path_check;
         const auto& column = tablet_schema.column(variant_schema_pos[i]);
         if (!column.is_variant_type()) {
             return Status::InternalError("column is not variant type, column name: {}",

diff --git a/be/src/util/json/json_parser.cpp b/be/src/util/json/json_parser.cpp
@@ -26,6 +26,7 @@
 #include <algorithm>
 #include <cassert>
 #include <string_view>
+#include <vector>
 
 #include "common/cast_set.h"
 // IWYU pragma: keep
@@ -46,6 +47,7 @@ std::optional<ParseResult> JSONDataParser<ParserImpl>::parse(const char* begin,
     // deprecated_enable_flatten_nested controls nested path traversal
     // NestedGroup expansion is now handled at storage layer
     context.deprecated_enable_flatten_nested = config.deprecated_enable_flatten_nested;
+    context.check_duplicate_json_path = config.check_duplicate_json_path;
     context.is_top_array = document.isArray();
     traverse(document, context);
     ParseResult result;
@@ -72,35 +74,57 @@ void JSONDataParser<ParserImpl>::traverse(const Element& element, ParseContext&
             // Parse nested arrays to JsonbField
             JsonbWriter writer;
             traverseArrayAsJsonb(element.getArray(), writer);
-            ctx.paths.push_back(ctx.builder.get_parts());
-            ctx.values.push_back(Field::create_field<TYPE_JSONB>(
-                    JsonbField(writer.getOutput()->getBuffer(), writer.getOutput()->getSize())));
+            tryAppendValue(
+                    ctx, ctx.builder.get_parts(),
+                    Field::create_field<TYPE_JSONB>(JsonbField(writer.getOutput()->getBuffer(),
+                                                               writer.getOutput()->getSize())));
         } else {
             traverseArray(element.getArray(), ctx);
         }
         // we should set has_nested_in_flatten to false when traverse array finished for next array otherwise it will be true for next array
         ctx.has_nested_in_flatten = false;
     } else {
-        ctx.paths.push_back(ctx.builder.get_parts());
-        ctx.values.push_back(getValueAsField(element));
+        tryAppendValue(ctx, ctx.builder.get_parts(), getValueAsField(element));
     }
 }
+
+template <typename ParserImpl>
+bool JSONDataParser<ParserImpl>::tryAppendValue(ParseContext& ctx, const PathInData::Parts& path,
+                                                Field&& value, bool check_duplicate_path) {
+    if (check_duplicate_path && ctx.check_duplicate_json_path) {
+        PathInData path_in_data(path);
+        if (!ctx.visited_path_names.emplace(path_in_data.get_path()).second) {
+            return false;
+        }
+    }
+    ctx.paths.push_back(path);
+    ctx.values.push_back(std::move(value));
+    return true;
+}
+
 template <typename ParserImpl>
 void JSONDataParser<ParserImpl>::traverseObject(const JSONObject& object, ParseContext& ctx) {
     ctx.paths.reserve(ctx.paths.size() + object.size());
     ctx.values.reserve(ctx.values.size() + object.size());
-    for (auto it = object.begin(); it != object.end(); ++it) {
-        const auto& [key, value] = *it;
+    auto check_key_length = [](const auto& key) {
         const size_t max_key_length = cast_set<size_t>(config::variant_max_json_key_length);
         if (key.size() > max_key_length) {
             throw doris::Exception(
                     doris::ErrorCode::INVALID_ARGUMENT,
                     fmt::format("Key length exceeds maximum allowed size of {} bytes.",
                                 max_key_length));
         }
+    };
+    auto traverse_object_member = [&](const auto& key, const auto& value) {
+        check_key_length(key);
         ctx.builder.append(key, false);
         traverse(value, ctx);
         ctx.builder.pop_back();
+    };
+
+    for (auto it = object.begin(); it != object.end(); ++it) {
+        const auto& [key, value] = *it;
+        traverse_object_member(key, value);
     }
 }
 
@@ -176,23 +200,24 @@ void JSONDataParser<ParserImpl>::traverseArray(const JSONArray& array, ParseCont
     ParseArrayContext array_ctx;
     array_ctx.has_nested_in_flatten = ctx.has_nested_in_flatten;
     array_ctx.is_top_array = ctx.is_top_array;
+    array_ctx.check_duplicate_json_path = ctx.check_duplicate_json_path;
     array_ctx.total_size = array.size();
     for (auto it = array.begin(); it != array.end(); ++it) {
         traverseArrayElement(*it, array_ctx);
         ++array_ctx.current_size;
     }
     auto&& arrays_by_path = array_ctx.arrays_by_path;
     if (arrays_by_path.empty()) {
-        ctx.paths.push_back(ctx.builder.get_parts());
-        ctx.values.push_back(Field::create_field<TYPE_ARRAY>(Array()));
+        tryAppendValue(ctx, ctx.builder.get_parts(), Field::create_field<TYPE_ARRAY>(Array()));
     } else {
         ctx.paths.reserve(ctx.paths.size() + arrays_by_path.size());
         ctx.values.reserve(ctx.values.size() + arrays_by_path.size());
         for (auto it = arrays_by_path.begin(); it != arrays_by_path.end(); ++it) {
             auto&& [path, path_array] = it->second;
             /// Merge prefix path and path of array element.
-            ctx.paths.push_back(ctx.builder.append(path, true).get_parts());
-            ctx.values.push_back(Field::create_field<TYPE_ARRAY>(std::move(path_array)));
+            ctx.builder.append(path, true);
+            tryAppendValue(ctx, ctx.builder.get_parts(),
+                           Field::create_field<TYPE_ARRAY>(std::move(path_array)));
             ctx.builder.pop_back(path.size());
         }
     }
@@ -204,10 +229,12 @@ void JSONDataParser<ParserImpl>::traverseArrayElement(const Element& element,
     ParseContext element_ctx;
     element_ctx.has_nested_in_flatten = ctx.has_nested_in_flatten;
     element_ctx.is_top_array = ctx.is_top_array;
+    element_ctx.check_duplicate_json_path = ctx.check_duplicate_json_path;
     traverse(element, element_ctx);
-    auto& [_, paths, values, deprecated_flatten_nested, __, is_top_array] = element_ctx;
+    auto& paths = element_ctx.paths;
+    auto& values = element_ctx.values;
 
-    if (element_ctx.has_nested_in_flatten && is_top_array) {
+    if (element_ctx.has_nested_in_flatten && element_ctx.is_top_array) {
         checkAmbiguousStructure(ctx, paths);
     }
 

diff --git a/be/src/util/json/json_parser.h b/be/src/util/json/json_parser.h
@@ -101,6 +101,7 @@ void writeValueAsJsonb(const Element& element, JsonbWriter& writer) {
 
 struct ParseConfig {
     bool deprecated_enable_flatten_nested = false;
+    bool check_duplicate_json_path = false;
     enum class ParseTo {
         OnlySubcolumns = 0,
         OnlyDocValueColumn = 1,
@@ -127,7 +128,9 @@ class JSONDataParser {
         PathInDataBuilder builder;
         std::vector<PathInData::Parts> paths;
         std::vector<Field> values;
+        phmap::flat_hash_set<std::string> visited_path_names;
         bool deprecated_enable_flatten_nested = false;
+        bool check_duplicate_json_path = false;
         bool has_nested_in_flatten = false;
         bool is_top_array = false;
     };
@@ -141,10 +144,13 @@ class JSONDataParser {
         KeyToSizes nested_sizes_by_key;
         bool has_nested_in_flatten = false;
         bool is_top_array = false;
+        bool check_duplicate_json_path = false;
     };
     void traverse(const Element& element, ParseContext& ctx);
     void traverseObject(const JSONObject& object, ParseContext& ctx);
     void traverseArray(const JSONArray& array, ParseContext& ctx);
+    bool tryAppendValue(ParseContext& ctx, const PathInData::Parts& path, Field&& value,
+                        bool check_duplicate_path = true);
     void traverseArrayElement(const Element& element, ParseArrayContext& ctx);
     void checkAmbiguousStructure(const ParseArrayContext& ctx,
                                  const std::vector<PathInData::Parts>& paths);