example of udf build added

Co-authored-by: Wey Gu <weyl.gu@gmail.com>
Co-authored-by: Cheng Xuntao <7731943+xtcyclist@users.noreply.github.com>

conf/nebula-graphd.conf.default

@@ -96,3 +96,9 @@
 
 # if use balance data feature, only work if enable_experimental_feature is true
 --enable_data_balance=true
+
+# enable udf, written in c++ only for now
+--enable_udf=true
+
+# set the directory where the .so files of udf are stored, when enable_udf is true
+--udf_path=/home/nebula/dev/nebula/udf/

src/common/function/FunctionManager.cpp

@@ -9,6 +9,7 @@
 
 #include <boost/algorithm/string/replace.hpp>
 
+#include "FunctionUdfManager.h"
 #include "common/base/Base.h"
 #include "common/datatypes/DataSet.h"
 #include "common/datatypes/Edge.h"
@@ -28,7 +29,6 @@
 #include "common/time/TimeUtils.h"
 #include "common/time/WallClock.h"
 #include "graph/service/GraphFlags.h"
-#include "FunctionUdfManager.h"
 
 DEFINE_bool(enable_udf, false, "enable udf");
 

src/common/function/FunctionUdfManager.cpp

@@ -1,7 +1,13 @@
+/* Copyright (c) 2020 vesoft inc. All rights reserved.
+ *
+ * This source code is licensed under Apache 2.0 License.
+ */
+
 #include "FunctionUdfManager.h"
 
 #include <dirent.h>
 #include <dlfcn.h>
+
 #include <cstring>
 #include <iostream>
 
@@ -47,7 +53,7 @@ std::vector<std::string> getFilesList(const std::string &path, const char *ftype
 }
 
 FunctionUdfManager::create_f *FunctionUdfManager::getGraphFunctionClass(void *func_handle) {
-  auto *create_func = (create_f *)dlsym(func_handle, "create");
+  auto *create_func = reinterpret_cast<create_f *>(dlsym(func_handle, "create"));
   dlsym_error = dlerror();
   if (dlsym_error) {
     LOG(ERROR) << "Cannot load symbol create: " << dlsym_error;
@@ -56,7 +62,7 @@ FunctionUdfManager::create_f *FunctionUdfManager::getGraphFunctionClass(void *fu
 }
 
 FunctionUdfManager::destroy_f *FunctionUdfManager::deleteGraphFunctionClass(void *func_handle) {
-  auto *destroy_func = (destroy_f *)dlsym(func_handle, "destroy");
+  auto *destroy_func = reinterpret_cast<destroy_f *>(dlsym(func_handle, "destroy"));
   dlsym_error = dlerror();
   if (dlsym_error) {
     LOG(ERROR) << "Cannot load symbol destroy: " << dlsym_error;
@@ -113,7 +119,6 @@ void FunctionUdfManager::initAndLoadSoFunction() {
 
       destroy_func(gf);
       dlclose(func_handle);
-
     } catch (...) {
       LOG(ERROR) << "load So library Error: " << soPath;
     }
@@ -196,4 +201,4 @@ void FunctionUdfManager::addSoUdfFunction(
   };
 }
 
-}  // namespace nebula
+}  // namespace nebula

src/common/function/FunctionUdfManager.h

@@ -1,3 +1,8 @@
+/* Copyright (c) 2020 vesoft inc. All rights reserved.
+ *
+ * This source code is licensed under Apache 2.0 License.
+ */
+
 #ifndef COMMON_FUNCTION_FUNCTIONUDFMANAGER_H_
 #define COMMON_FUNCTION_FUNCTIONUDFMANAGER_H_
 
@@ -13,7 +18,8 @@ class FunctionUdfManager {
   typedef GraphFunction *(create_f)();
   typedef void(destroy_f)(GraphFunction *);
 
-  static StatusOr<Value::Type> getUdfReturnType(const std::string functionName, const std::vector<Value::Type> &argsType);
+  static StatusOr<Value::Type> getUdfReturnType(const std::string functionName,
+                                                const std::vector<Value::Type> &argsType);
 
   static StatusOr<const FunctionManager::FunctionAttributes> loadUdfFunction(
       std::string functionName, size_t arity);
@@ -28,7 +34,6 @@ class FunctionUdfManager {
 
   void addSoUdfFunction(char *funName, const char *soPath, size_t i, size_t i1, bool b);
   void initAndLoadSoFunction();
-
 };
 
 }  // namespace nebula

src/common/function/GraphFunction.h

@@ -1,7 +1,13 @@
+/* Copyright (c) 2020 vesoft inc. All rights reserved.
+ *
+ * This source code is licensed under Apache 2.0 License.
+ */
+
 #ifndef COMMON_FUNCTION_GRAPHFUNCTION_H
 #define COMMON_FUNCTION_GRAPHFUNCTION_H
 
 #include <vector>
+
 #include "common/datatypes/Value.h"
 
 class GraphFunction;
@@ -10,23 +16,23 @@ extern "C" GraphFunction *create();
 extern "C" void destroy(GraphFunction *function);
 
 class GraphFunction {
-public:
-    virtual ~GraphFunction() = default;
+ public:
+  virtual ~GraphFunction() = default;
 
-    virtual char *name() = 0;
+  virtual char *name() = 0;
 
-    virtual std::vector<std::vector<nebula::Value::Type>> inputType() = 0;
+  virtual std::vector<std::vector<nebula::Value::Type>> inputType() = 0;
 
-    virtual nebula::Value::Type returnType() = 0;
+  virtual nebula::Value::Type returnType() = 0;
 
-    virtual size_t minArity() = 0;
+  virtual size_t minArity() = 0;
 
-    virtual size_t maxArity() = 0;
+  virtual size_t maxArity() = 0;
 
-    virtual bool isPure() = 0;
+  virtual bool isPure() = 0;
 
-    virtual nebula::Value body(const std::vector<std::reference_wrapper<const nebula::Value>> &args) = 0;
+  virtual nebula::Value body(
+      const std::vector<std::reference_wrapper<const nebula::Value>> &args) = 0;
 };
 
 #endif  // COMMON_FUNCTION_GRAPHFUNCTION_H
-

udf/standard_deviation.cpp

@@ -0,0 +1,91 @@
+/* Copyright (c) 2020 vesoft inc. All rights reserved.
+ *
+ * This source code is licensed under Apache 2.0 License.
+ */
+
+#include "standard_deviation.h"
+
+#include <cmath>
+#include <vector>
+
+#include "../src/common/datatypes/List.h"
+
+extern "C" GraphFunction *create() {
+  return new standard_deviation;
+}
+extern "C" void destroy(GraphFunction *function) {
+  delete function;
+}
+
+char *standard_deviation::name() {
+  const char *name = "standard_deviation";
+  return const_cast<char *>(name);
+}
+
+std::vector<std::vector<nebula::Value::Type>> standard_deviation::inputType() {
+  std::vector<nebula::Value::Type> vtp = {nebula::Value::Type::LIST};
+  std::vector<std::vector<nebula::Value::Type>> vvtp = {vtp};
+  return vvtp;
+}
+
+nebula::Value::Type standard_deviation::returnType() {
+  return nebula::Value::Type::FLOAT;
+}
+
+size_t standard_deviation::minArity() {
+  return 1;
+}
+
+size_t standard_deviation::maxArity() {
+  return 1;
+}
+
+bool standard_deviation::isPure() {
+  return true;
+}
+
+double caculate_standard_deviation(const std::vector<double> &numbers) {
+  double sum = 0;
+  for (double number : numbers) {
+    sum += number;
+  }
+  double average = sum / numbers.size();
+
+  double variance = 0;
+  for (double number : numbers) {
+    double difference = number - average;
+    variance += difference * difference;
+  }
+  variance /= numbers.size();
+
+  return sqrt(variance);
+}
+
+nebula::Value standard_deviation::body(
+    const std::vector<std::reference_wrapper<const nebula::Value>> &args) {
+  switch (args[0].get().type()) {
+    case nebula::Value::Type::NULLVALUE: {
+      return nebula::Value::kNullValue;
+    }
+    case nebula::Value::Type::LIST: {
+      std::vector<double> numbers;
+      auto list = args[0].get().getList();
+      auto size = list.size();
+
+      for (int i = 0; i < size; i++) {
+        auto &value = list[i];
+        if (value.isInt()) {
+          numbers.push_back(value.getInt());
+        } else if (value.isFloat()) {
+          numbers.push_back(value.getFloat());
+        } else {
+          return nebula::Value::kNullValue;
+        }
+      }
+      return nebula::Value(caculate_standard_deviation(numbers));
+    }
+    default: {
+      return nebula::Value::kNullValue;
+    }
+  }
+}

udf/standard_deviation.h

@@ -0,0 +1,51 @@
+/* Copyright (c) 2020 vesoft inc. All rights reserved.
+ *
+ * This source code is licensed under Apache 2.0 License.
+ */
+
+#ifndef UDF_PROJECT_STANDARD_DEVIATION_H
+#define UDF_PROJECT_STANDARD_DEVIATION_H
+
+#include "../src/common/function/GraphFunction.h"
+
+// Example of a UDF function that calculates the standard deviation of a set of numbers.
+// > YIELD standard_deviation([1,2,3])
+// +-----------------------------+
+// | standard_deviation([1,2,3]) |
+// +-----------------------------+
+// | 0.816496580927726           |
+// +-----------------------------+
+
+// > YIELD standard_deviation([1,1,1])
+// +-----------------------------+
+// | standard_deviation([1,1,1]) |
+// +-----------------------------+
+// | 0.0                         |
+// +-----------------------------+
+
+// > GO 1 TO 2 STEPS FROM "player100" OVER follow YIELD properties(edge).degree AS d | yield collect($-.d)
+// +--------------------------+
+// | collect($-.d)            |
+// +--------------------------+
+// | [95, 95, 95, 90, 95, 90] |
+// +--------------------------+
+
+
+class standard_deviation : public GraphFunction {
+ public:
+  char *name() override;
+
+  std::vector<std::vector<nebula::Value::Type>> inputType() override;
+
+  nebula::Value::Type returnType() override;
+
+  size_t minArity() override;
+
+  size_t maxArity() override;
+
+  bool isPure() override;
+
+  nebula::Value body(const std::vector<std::reference_wrapper<const nebula::Value>> &args) override;
+};
+
+#endif  // UDF_PROJECT_STANDARD_DEVIATION_H