ARROW-10392: [C++][Gandiva] Avoid string copy while evaluating IN expression

cpp/src/gandiva/gdv_function_stubs.cc

@@ -94,7 +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));
+ 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

@@ -20,6 +20,7 @@
 #include <string>
 #include <unordered_set>
 
+#include "arrow/util/hashing.h"
 #include "gandiva/arrow.h"
 #include "gandiva/gandiva_aliases.h"
 
@@ -42,4 +43,30 @@ 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:
+ struct string_view_hash {
+ public:
+ std::size_t operator()(arrow::util::string_view v) const {
+ return arrow::internal::ComputeStringHash<0>(v.data(), v.length());
+ }
+ };
+
+ std::unordered_set<arrow::util::string_view, string_view_hash> values_lookup_;
+ const std::unordered_set<std::string> values_;
+};
+
 } // namespace gandiva