specialize in holder impl for strings

Author: pprudhvi

cpp/src/arrow/stl_allocator.h

@@ -32,7 +32,7 @@ namespace stl {
 
 /// \brief A STL allocator delegating allocations to a Arrow MemoryPool
 template <class T>
-class allocator : public std::allocator<T> {
+class allocator {
  public:
   using value_type = T;
   using pointer = T*;

cpp/src/gandiva/gdv_function_stubs.cc

@@ -20,7 +20,6 @@
 #include <string>
 #include <vector>
 
-#include "arrow/stl_allocator.h"
 #include "arrow/util/value_parsing.h"
 #include "gandiva/engine.h"
 #include "gandiva/exported_funcs.h"
@@ -95,7 +94,7 @@ bool gdv_fn_in_expr_lookup_utf8(int64_t ptr, const char* data, int data_len,
   }
   gandiva::InHolder<std::string>* holder =
       reinterpret_cast<gandiva::InHolder<std::string>*>(ptr);
-  return holder->HasValue(std::string(data, data_len, ::arrow::stl::allocator<char>()));
+  return holder->HasValue(arrow::util::string_view(data, data_len));
 }
 
 int32_t gdv_fn_populate_varlen_vector(int64_t context_ptr, int8_t* data_ptr,

cpp/src/gandiva/in_holder.h

@@ -42,4 +42,23 @@ class InHolder {
   std::unordered_set<Type> values_;
 };
 
+template <>
+class InHolder<std::string> {
+ public:
+  explicit InHolder(std::unordered_set<std::string> values) : values_(std::move(values)) {
+    values_lookup_.max_load_factor(0.25f);
+    for (const std::string& value : values_) {
+      values_lookup_.emplace(value);
+    }
+  }
+
+  bool HasValue(arrow::util::string_view value) const {
+    return values_lookup_.count(value) == 1;
+  }
+
+ private:
+  std::unordered_set<arrow::util::string_view> values_lookup_;
+  const std::unordered_set<std::string> values_;
+};
+
 }  // namespace gandiva