Fix json input format ignore field key case

src/Core/FormatFactorySettings.h

@@ -472,6 +472,7 @@ Enabled by default.
     DECLARE(Bool, input_format_json_ignore_unnecessary_fields, true, R"(
 Ignore unnecessary fields and not parse them. Enabling this may not throw exceptions on json strings of invalid format or with duplicated fields
 )", 0) \
+    DECLARE(Bool, input_format_json_case_insensitive_column_matching, false, R"(Ignore json key case while read json field from string)", 0) \
     DECLARE(Bool, input_format_try_infer_variants, false, R"(
 If enabled, ClickHouse will try to infer type [`Variant`](../../sql-reference/data-types/variant.md) in schema inference for text formats when there is more than one possible type for column/array elements.
 

src/Core/SettingsChangesHistory.cpp

@@ -77,6 +77,7 @@ static std::initializer_list<std::pair<ClickHouseVersion, SettingsChangesHistory
             {"backup_restore_keeper_max_retries_while_handling_error", 0, 20, "New setting."},
             {"backup_restore_finish_timeout_after_error_sec", 0, 180, "New setting."},
             {"parallel_replicas_local_plan", false, true, "Use local plan for local replica in a query with parallel replicas"},
+            {"input_format_json_case_insensitive_column_matching", false, false, "Ignore json key case while read json field from string."},
         }
     },
     {"24.10",

src/Formats/FormatFactory.cpp

@@ -182,6 +182,7 @@ FormatSettings getFormatSettings(const ContextPtr & context, const Settings & se
     format_settings.json.ignore_unnecessary_fields = settings[Setting::input_format_json_ignore_unnecessary_fields];
     format_settings.json.empty_as_default = settings[Setting::input_format_json_empty_as_default];
     format_settings.json.type_json_skip_duplicated_paths = settings[Setting::type_json_skip_duplicated_paths];
+    format_settings.json.case_insensitive_column_matching = settings[Setting::input_format_json_case_insensitive_column_matching];
     format_settings.null_as_default = settings[Setting::input_format_null_as_default];
     format_settings.force_null_for_omitted_fields = settings[Setting::input_format_force_null_for_omitted_fields];
     format_settings.decimal_trailing_zeros = settings[Setting::output_format_decimal_trailing_zeros];

src/Formats/FormatSettings.h

@@ -244,6 +244,7 @@ struct FormatSettings
         bool ignore_unnecessary_fields = true;
         bool empty_as_default = false;
         bool type_json_skip_duplicated_paths = false;
+        bool case_insensitive_column_matching = false;
     } json{};
 
     struct

src/Processors/Formats/Impl/JSONEachRowRowInputFormat.cpp

@@ -9,6 +9,7 @@
 #include <DataTypes/NestedUtils.h>
 #include <DataTypes/Serializations/SerializationNullable.h>
 #include <DataTypes/getLeastSupertype.h>
+#include <boost/algorithm/string/case_conv.hpp>
 
 namespace DB
 {
@@ -46,6 +47,15 @@ JSONEachRowRowInputFormat::JSONEachRowRowInputFormat(
 {
     const auto & header = getPort().getHeader();
     name_map = header.getNamesToIndexesMap();
+    if (format_settings_.json.case_insensitive_column_matching)
+    {
+        for (auto & it : name_map)
+        {
+            String key = it.first.toString();
+            boost::to_lower(key);
+            lower_case_name_map[key] = it.first;
+        }
+    }
     if (format_settings_.import_nested_json)
     {
         for (size_t i = 0; i != header.columns(); ++i)
@@ -168,7 +178,16 @@ void JSONEachRowRowInputFormat::readJSONObject(MutableColumns & columns)
             skipUnknownField(name_ref);
             continue;
         }
-        const size_t column_index = columnIndex(name_ref, key_index);
+        size_t column_index = 0;
+        if (format_settings.json.case_insensitive_column_matching)
+        {
+            String field_name = name_ref.toString();
+            boost::to_lower(field_name);
+            StringRef field_name_ref = lower_case_name_map[field_name];
+            column_index = columnIndex(field_name_ref, key_index);
+        }
+        else
+            column_index = columnIndex(name_ref, key_index);
 
         if (unlikely(ssize_t(column_index) < 0))
         {

src/Processors/Formats/Impl/JSONEachRowRowInputFormat.h

@@ -76,6 +76,9 @@ class JSONEachRowRowInputFormat : public IRowInputFormat
     /// Hash table match `field name -> position in the block`. NOTE You can use perfect hash map.
     Block::NameMap name_map;
 
+    /// Hash table match `lower_case field name -> field name in the block`.
+    std::unordered_map<String, StringRef> lower_case_name_map;
+
     /// Cached search results for previous row (keyed as index in JSON object) - used as a hint.
     std::vector<Block::NameMap::const_iterator> prev_positions;