Support retrieving function metadata

velox/expression/VectorFunction.cpp

@@ -70,6 +70,13 @@ std::optional<std::vector<FunctionSignaturePtr>> getVectorFunctionSignatures(
       });
 }
 
+std::optional<VectorFunctionMetadata> getVectorFunctionMetadata(
+    const std::string& name) {
+  return applyToVectorFunctionEntry<VectorFunctionMetadata>(
+      name,
+      [&](const auto& /*name*/, const auto& entry) { return entry.metadata; });
+}
+
 TypePtr resolveVectorFunction(
     const std::string& functionName,
     const std::vector<TypePtr>& argTypes) {

velox/expression/VectorFunction.h

@@ -175,6 +175,11 @@ class SimpleFunctionAdapterFactory {
 std::optional<std::vector<FunctionSignaturePtr>> getVectorFunctionSignatures(
     const std::string& name);
 
+/// Returns metadata corresponding to function with the specified name. Returns
+/// std::nullopt if there is no function with the specified name.
+std::optional<VectorFunctionMetadata> getVectorFunctionMetadata(
+    const std::string& name);
+
 /// Given name of vector function and argument types, returns
 /// the return type if function exists and have a signature that binds to the
 /// input types otherwise returns nullptr.

velox/functions/CoverageUtil.h

@@ -20,6 +20,15 @@
 
 namespace facebook::velox::functions {
 
+// Returns sorted list of scalar function names available in Velox.
+std::vector<std::string> getSortedScalarNames();
+
+// Returns sorted list of aggregate function names available in Velox.
+std::vector<std::string> getSortedAggregateNames();
+
+// Returns sorted list of window function names available in Velox.
+std::vector<std::string> getSortedWindowNames();
+
 // Print a rst format string which contains all Presto/Spark scalar
 // functions and aggragate functions. This function will read
 // all_scalar_functions.txt and all_aggregate_functions.txt from certain path.

velox/functions/FunctionRegistry.cpp

@@ -122,4 +122,23 @@ resolveVectorFunctionWithMetadata(
   return exec::resolveVectorFunctionWithMetadata(functionName, argTypes);
 }
 
+exec::VectorFunctionMetadata getFunctionMetadata(
+    const std::string& functionName) {
+  auto simpleFunctionMetadata =
+      exec::simpleFunctions().getFunctionSignaturesAndMetadata(functionName);
+  if (simpleFunctionMetadata.size()) {
+    // Functions like abs are registered as simple functions for primitive
+    // types, and as a vector function for complex types like DECIMAL. So do not
+    // throw an error if function metadata is not found in simple function
+    // signature map.
+    return simpleFunctionMetadata.back().first;
+  }
+
+  auto vectorFunctionMetadata = exec::getVectorFunctionMetadata(functionName);
+  if (vectorFunctionMetadata.has_value()) {
+    return vectorFunctionMetadata.value();
+  }
+  VELOX_USER_FAIL("Metadata not found for scalar function {}", functionName);
+}
+
 } // namespace facebook::velox

velox/functions/FunctionRegistry.h

@@ -76,4 +76,8 @@ resolveVectorFunctionWithMetadata(
 /// Clears the function registry.
 void clearFunctionRegistry();
 
+/// Get the function metadata corresponding to functionName.
+exec::VectorFunctionMetadata getFunctionMetadata(
+    const std::string& functionName);
+
 } // namespace facebook::velox