From 1174fc346bba33285a8be96e50d8c947edac46c5 Mon Sep 17 00:00:00 2001
From: VDimir <Vdimir@users.noreply.github.com>
Date: Sat, 12 Oct 2019 11:42:43 +0000
Subject: [PATCH] Add isValidJSON function

---
 dbms/src/Functions/FunctionsJSON.cpp          |  1 +
 dbms/src/Functions/FunctionsJSON.h            | 23 ++++++++++++++++---
 .../00918_json_functions.reference            |  4 ++++
 .../0_stateless/00918_json_functions.sql      |  5 ++++
 4 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/dbms/src/Functions/FunctionsJSON.cpp b/dbms/src/Functions/FunctionsJSON.cpp
index 62413ce58d4..eedbecf852d 100644
--- a/dbms/src/Functions/FunctionsJSON.cpp
+++ b/dbms/src/Functions/FunctionsJSON.cpp
@@ -8,6 +8,7 @@ namespace DB
 void registerFunctionsJSON(FunctionFactory & factory)
 {
     factory.registerFunction<FunctionJSON<NameJSONHas, JSONHasImpl>>();
+    factory.registerFunction<FunctionJSON<NameIsValidJSON, isValidJSONImpl>>();
     factory.registerFunction<FunctionJSON<NameJSONLength, JSONLengthImpl>>();
     factory.registerFunction<FunctionJSON<NameJSONKey, JSONKeyImpl>>();
     factory.registerFunction<FunctionJSON<NameJSONType, JSONTypeImpl>>();
diff --git a/dbms/src/Functions/FunctionsJSON.h b/dbms/src/Functions/FunctionsJSON.h
index b9fddf57d39..ee556f480d7 100644
--- a/dbms/src/Functions/FunctionsJSON.h
+++ b/dbms/src/Functions/FunctionsJSON.h
@@ -279,6 +279,7 @@ private:
 
 
 struct NameJSONHas { static constexpr auto name{"JSONHas"}; };
+struct NameIsValidJSON { static constexpr auto name{"isValidJSON"}; };
 struct NameJSONLength { static constexpr auto name{"JSONLength"}; };
 struct NameJSONKey { static constexpr auto name{"JSONKey"}; };
 struct NameJSONType { static constexpr auto name{"JSONType"}; };
@@ -292,11 +293,23 @@ struct NameJSONExtractKeysAndValues { static constexpr auto name{"JSONExtractKey
 struct NameJSONExtractRaw { static constexpr auto name{"JSONExtractRaw"}; };
 
 
-template <typename JSONParser>
-class JSONHasImpl
+template <typename JSONParser, bool support_key_lookup>
+class JSONCheckImpl
 {
 public:
-    static DataTypePtr getType(const char *, const ColumnsWithTypeAndName &) { return std::make_shared<DataTypeUInt8>(); }
+    static DataTypePtr getType(const char * function_name, const ColumnsWithTypeAndName & arguments) {
+        if constexpr (!support_key_lookup) {
+            if (arguments.size() != 1)
+                throw Exception{"Function " + String(function_name) + " needs exactly one argument",
+                                ErrorCodes::NUMBER_OF_ARGUMENTS_DOESNT_MATCH};
+        }
+        else
+        {
+            UNUSED(function_name);
+            UNUSED(arguments);
+        }
+        return std::make_shared<DataTypeUInt8>();
+    }
 
     using Iterator = typename JSONParser::Iterator;
     static bool addValueToColumn(IColumn & dest, const Iterator &)
@@ -310,6 +323,10 @@ public:
     static void prepare(const char *, const Block &, const ColumnNumbers &, size_t) {}
 };
 
+template <typename JSONParser>
+using JSONHasImpl = JSONCheckImpl<JSONParser, true>;
+template <typename JSONParser>
+using isValidJSONImpl = JSONCheckImpl<JSONParser, false>;
 
 template <typename JSONParser>
 class JSONLengthImpl
diff --git a/dbms/tests/queries/0_stateless/00918_json_functions.reference b/dbms/tests/queries/0_stateless/00918_json_functions.reference
index a23b177d468..181da3dd3a0 100644
--- a/dbms/tests/queries/0_stateless/00918_json_functions.reference
+++ b/dbms/tests/queries/0_stateless/00918_json_functions.reference
@@ -7,6 +7,10 @@
 1
 1
 0
+--isValidJSON--
+1
+0
+0
 --JSONKey--
 a
 b
diff --git a/dbms/tests/queries/0_stateless/00918_json_functions.sql b/dbms/tests/queries/0_stateless/00918_json_functions.sql
index 38bf0a7ffec..4cb2445ca2a 100644
--- a/dbms/tests/queries/0_stateless/00918_json_functions.sql
+++ b/dbms/tests/queries/0_stateless/00918_json_functions.sql
@@ -11,6 +11,11 @@ SELECT JSONHas('{"a": "hello", "b": [-100, 200.0, 300]}', 'a');
 SELECT JSONHas('{"a": "hello", "b": [-100, 200.0, 300]}', 'b');
 SELECT JSONHas('{"a": "hello", "b": [-100, 200.0, 300]}', 'c');
 
+SELECT '--isValidJSON--';
+SELECT isValidJSON('{"a": "hello", "b": [-100, 200.0, 300]}');
+SELECT isValidJSON('not a json');
+SELECT isValidJSON('"HX-=');
+
 SELECT '--JSONKey--';
 SELECT JSONKey('{"a": "hello", "b": [-100, 200.0, 300]}', 1);
 SELECT JSONKey('{"a": "hello", "b": [-100, 200.0, 300]}', 2);