[Exec)(cache) add element count in LRU cache (#41199)

add element_count() in LRU cache

be/src/olap/lru_cache.cpp

@@ -700,6 +700,14 @@ int64_t ShardedLRUCache::get_usage() {
  return total_usage;
 }
 
+size_t ShardedLRUCache::get_element_count() {
+ size_t total_element_count = 0;
+ for (int i = 0; i < _num_shards; i++) {
+ total_element_count += _shards[i]->get_element_count();
+ }
+ return total_element_count;
+}
+
 void ShardedLRUCache::update_cache_metrics() const {
  size_t capacity = 0;
  size_t total_usage = 0;

be/src/olap/lru_cache.h

@@ -230,6 +230,8 @@ class Cache {
  virtual PrunedInfo set_capacity(size_t capacity) = 0;
  virtual size_t get_capacity() = 0;
 
+ virtual size_t get_element_count() = 0;
+
 private:
  DISALLOW_COPY_AND_ASSIGN(Cache);
 };
@@ -404,6 +406,7 @@ class ShardedLRUCache : public Cache {
  PrunedInfo prune() override;
  PrunedInfo prune_if(CachePrunePredicate pred, bool lazy_mode = false) override;
  int64_t get_usage() override;
+ size_t get_element_count() override;
  PrunedInfo set_capacity(size_t capacity) override;
  size_t get_capacity() override;
 
@@ -467,6 +470,7 @@ class DummyLRUCache : public Cache {
  int64_t get_usage() override { return 0; };
  PrunedInfo set_capacity(size_t capacity) override { return {0, 0}; };
  size_t get_capacity() override { return 0; };
+ size_t get_element_count() override { return 0; };
 };
 
 } // namespace doris

be/src/pipeline/query_cache/query_cache.cpp

@@ -66,4 +66,4 @@ bool QueryCache::lookup(const CacheKey& key, int64_t version, doris::QueryCacheH
  return false;
 }
 
-} // namespace doris
+} // namespace doris

be/src/runtime/memory/lru_cache_policy.h

@@ -132,6 +132,8 @@ class LRUCachePolicy : public CachePolicy {
 
  int64_t get_usage() { return _cache->get_usage(); }
 
+ size_t get_element_count() { return _cache->get_element_count(); }
+
  size_t get_capacity() override { return _cache->get_capacity(); }
 
  uint64_t new_id() { return _cache->new_id(); };