fix(funcexp): MCOL-5607: JSON function use crashes query execution (#3028)

JSON functions were implemented violating an assumption of their
pureness, as they should not have any state. This concrete patch
fixes implementation of JSON_VALUE function.

mysql-test/columnstore/basic/r/MCOL-5607-json-value-fix.result

@@ -0,0 +1,34 @@
+DROP DATABASE IF EXISTS MCOL5607;
+CREATE DATABASE MCOL5607;
+USE MCOL5607;
+CREATE TABLE zu (hu TEXT) ENGINE = COLUMNSTORE;
+INSERT INTO zu(hu) VALUES ('{}'), (NULL), ('{ "": "huh", "10001" : "10001", "10002" : "10001", "10003" : "10001", "10004" : "10001", "10005" : "10001", "10006" : "10001", "10007" : "10001", "10008" : "10001", "10009" : "10001", "10010" : "10001", "10011" : "10001", "10012" : "10001", "10013" : "10001", "10014" : "10001", "10015" : "10001", "10016" : "10001", "10017" : "10001", "10018" : "10001", "10019" : "10001", "10020" : "10001", "buga" : ""}');
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+SELECT COUNT(*) FROM zu;
+COUNT(*)
+3145728
+SELECT COUNT(*) FROM zu wHERE
+JSON_VALUE(hu, '$.buga') IS NOT NULL
+AND     JSON_VALUE(hu, '$.zhuga') IS NULL;
+COUNT(*)
+1048576
+DROP DATABASE MCOL5607;

mysql-test/columnstore/basic/t/MCOL-5607-json-value-fix.test

@@ -0,0 +1,32 @@
+--disable_warnings
+DROP DATABASE IF EXISTS MCOL5607;
+--enable_warnings
+CREATE DATABASE MCOL5607;
+USE MCOL5607;
+CREATE TABLE zu (hu TEXT) ENGINE = COLUMNSTORE;
+INSERT INTO zu(hu) VALUES ('{}'), (NULL), ('{ "": "huh", "10001" : "10001", "10002" : "10001", "10003" : "10001", "10004" : "10001", "10005" : "10001", "10006" : "10001", "10007" : "10001", "10008" : "10001", "10009" : "10001", "10010" : "10001", "10011" : "10001", "10012" : "10001", "10013" : "10001", "10014" : "10001", "10015" : "10001", "10016" : "10001", "10017" : "10001", "10018" : "10001", "10019" : "10001", "10020" : "10001", "buga" : ""}');
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+INSERT INTO zu(hu) SELECT hu FROM zu;
+SELECT COUNT(*) FROM zu;
+SELECT COUNT(*) FROM zu wHERE
+        JSON_VALUE(hu, '$.buga') IS NOT NULL
+AND     JSON_VALUE(hu, '$.zhuga') IS NULL;
+DROP DATABASE MCOL5607;

utils/funcexp/func_json_value.cpp

@@ -65,27 +65,17 @@ bool JSONPathWrapper::extract(std::string& ret, rowgroup::Row& row, execplan::SP
 
   const string& js = funcParamJS->data()->getStrVal(row, isNullJS);
   const string_view jsp = funcParamPath->data()->getStrVal(row, isNullPath);
+  
   if (isNullJS || isNullPath)
     return true;
 
   int error = 0;
 
-  if (!parsed)
+  if (json_path_setup(&p, getCharset(funcParamPath), (const uchar*)jsp.data(),
-  {
+                                                     (const uchar*)jsp.data() + jsp.size()))
-    if (!constant)
+    return true;
-    {
-      ConstantColumn* constCol = dynamic_cast<ConstantColumn*>(funcParamPath->data());
-      constant = (constCol != nullptr);
-    }
 
-    if (isNullPath || json_path_setup(&p, getCharset(funcParamPath), (const uchar*)jsp.data(),
+  JSONEgWrapper je(getCharset(funcParamJS), (const uchar*)js.data(), (const uchar*)js.data() + js.size());
-                                      (const uchar*)jsp.data() + jsp.size()))
-      return true;
-
-    parsed = constant;
-  }
-
-  JSONEgWrapper je(js, getCharset(funcParamJS));
 
   currStep = p.steps;
 
@@ -112,11 +102,29 @@ CalpontSystemCatalog::ColType Func_json_value::operationType(FunctionParm& fp,
   return fp[0]->data()->resultType();
 }
 
+class JSONPathWrapperValue : public JSONPathWrapper
+{
+ public:
+  JSONPathWrapperValue()
+  {
+  }
+  virtual ~JSONPathWrapperValue()
+  {
+  }
+
+  bool checkAndGetValue(JSONEgWrapper* je, string& res, int* error) override
+  {
+    return je->checkAndGetScalar(res, error);
+  }
+
+};
+
 string Func_json_value::getStrVal(rowgroup::Row& row, FunctionParm& fp, bool& isNull,
                                   execplan::CalpontSystemCatalog::ColType& type)
 {
   string ret;
-  isNull = JSONPathWrapper::extract(ret, row, fp[0], fp[1]);
+  JSONPathWrapperValue pw;
+  isNull = pw.extract(ret, row, fp[0], fp[1]);
   return isNull ? "" : ret;
 }
 }  // namespace funcexp

utils/funcexp/functor.h

@@ -54,6 +54,11 @@ namespace funcexp
 typedef std::vector<execplan::SPTP> FunctionParm;
 
 /** @brief Func class
+ *
+ * @desc IMPORTANT: functions are pure transformers, they should
+ * not have state shared between invocations. This is so because
+ * functions' objects are, essentially, singletons and the same
+ * objects will be used in diffeent threads.
  */
 class Func
 {

utils/funcexp/functor_json.h

@@ -56,6 +56,7 @@ class JSONPathWrapper : public JSONPath
   {
   }
   virtual bool checkAndGetValue(JSONEgWrapper* je, std::string& ret, int* error) = 0;
+ public:
   bool extract(std::string& ret, rowgroup::Row& row, execplan::SPTP& funcParmJS,
                execplan::SPTP& funcParmPath);
 };
@@ -381,7 +382,7 @@ class Func_json_merge_patch : public Func_Str
 
 /** @brief Func_json_value class
  */
-class Func_json_value : public Func_Str, public JSONPathWrapper
+class Func_json_value : public Func_Str
 {
  public:
   Func_json_value() : Func_Str("json_value")
@@ -391,11 +392,6 @@ class Func_json_value : public Func_Str, public JSONPathWrapper
   {
   }
 
-  bool checkAndGetValue(JSONEgWrapper* je, string& res, int* error) override
-  {
-    return je->checkAndGetScalar(res, error);
-  }
-
   execplan::CalpontSystemCatalog::ColType operationType(
       FunctionParm& fp, execplan::CalpontSystemCatalog::ColType& resultType) override;