DX-24414: Make gandiva cache size configurable (#16)

cpp/src/gandiva/cache.h

@@ -17,6 +17,8 @@
 
 #pragma once
 
+#include <cstdlib>
+#include <iostream>
 #include <mutex>
 
 #include "gandiva/lru_cache.h"
@@ -26,7 +28,12 @@ namespace gandiva {
 template <class KeyType, typename ValueType>
 class Cache {
  public:
- explicit Cache(size_t capacity = CACHE_SIZE) : cache_(capacity) {}
+ explicit Cache(size_t capacity) : cache_(capacity) {
+ std::cout << "Creating gandiva cache with capacity: " << capacity << std::endl;
+ }
+
+ Cache() : Cache(GetCapacity()) {}
+
  ValueType GetModule(KeyType cache_key) {
  arrow::util::optional<ValueType> result;
  mtx_.lock();
@@ -42,8 +49,24 @@ class Cache {
  }
 
  private:
+ static int GetCapacity() {
+ int capacity;
+ const char* env_cache_size = std::getenv("GANDIVA_CACHE_SIZE");
+ if (env_cache_size != nullptr) {
+ capacity = std::atoi(env_cache_size);
+ if (capacity <= 0) {
+ std::cout << "Invalid cache size provided. Using default cache size."
+ << std::endl;
+ capacity = DEFAULT_CACHE_SIZE;
+ }
+ } else {
+ capacity = DEFAULT_CACHE_SIZE;
+ }
+ return capacity;
+ }
+
  LruCache<KeyType, ValueType> cache_;
- static const int CACHE_SIZE = 250;
+ static const int DEFAULT_CACHE_SIZE = 500;
  std::mutex mtx_;
 };
 } // namespace gandiva

cpp/src/gandiva/lru_cache.h

@@ -18,6 +18,7 @@
 #pragma once
 
 #include <list>
+#include <iostream>
 #include <unordered_map>
 #include <utility>
 
@@ -107,6 +108,7 @@ class LruCache {
 
  private:
  void evict() {
+ std::cout << "Evicted a cache item from the lru cache" << std::endl;
  // evict item from the end of most recently used list
  typename list_type::iterator i = --lru_list_.end();
  map_.erase(*i);