From f1450923cbb3c836c833c1d3825ffae968894769 Mon Sep 17 00:00:00 2001
From: Robert Schulze <robert@clickhouse.com>
Date: Mon, 13 Mar 2023 15:28:03 +0000
Subject: [PATCH] Extend CacheBase with dump() method

---
 src/Common/CacheBase.h       | 7 +++++++
 src/Common/ICachePolicy.h    | 8 ++++++++
 src/Common/LRUCachePolicy.h  | 9 +++++++++
 src/Common/SLRUCachePolicy.h | 9 +++++++++
 4 files changed, 33 insertions(+)

diff --git a/src/Common/CacheBase.h b/src/Common/CacheBase.h
index 89aa78b390c..f38c3943f09 100644
--- a/src/Common/CacheBase.h
+++ b/src/Common/CacheBase.h
@@ -37,6 +37,7 @@ public:
     using Key = typename CachePolicy::Key;
     using Mapped = typename CachePolicy::Mapped;
     using MappedPtr = typename CachePolicy::MappedPtr;
+    using KeyMapped = typename CachePolicy::KeyMapped;
 
     /// Use this ctor if you don't care about the internal cache policy.
     explicit CacheBase(size_t max_size_in_bytes, size_t max_entries = 0, double size_ratio = 0.5)
@@ -160,6 +161,12 @@ public:
         out_misses = misses;
     }
 
+    std::vector<KeyMapped> dump() const
+    {
+        std::lock_guard lock(mutex);
+        return cache_policy->dump();
+    }
+
     void reset()
     {
         std::lock_guard lock(mutex);
diff --git a/src/Common/ICachePolicy.h b/src/Common/ICachePolicy.h
index f14e5b30c4f..c9d5bb282f6 100644
--- a/src/Common/ICachePolicy.h
+++ b/src/Common/ICachePolicy.h
@@ -25,6 +25,12 @@ public:
     using MappedPtr = std::shared_ptr<Mapped>;
     using OnWeightLossFunction = std::function<void(size_t)>;
 
+    struct KeyMapped
+    {
+        Key key;
+        MappedPtr mapped;
+    };
+
     virtual size_t weight(std::lock_guard<std::mutex> & /* cache_lock */) const = 0;
     virtual size_t count(std::lock_guard<std::mutex> & /* cache_lock */) const = 0;
     virtual size_t maxSize(std::lock_guard<std::mutex>& /* cache_lock */) const = 0;
@@ -34,6 +40,8 @@ public:
     virtual MappedPtr get(const Key & key, std::lock_guard<std::mutex> & /* cache_lock */) = 0;
     virtual void set(const Key & key, const MappedPtr & mapped, std::lock_guard<std::mutex> & /* cache_lock */) = 0;
 
+    virtual std::vector<KeyMapped> dump() const = 0;
+
     virtual ~ICachePolicy() = default;
 };
 
diff --git a/src/Common/LRUCachePolicy.h b/src/Common/LRUCachePolicy.h
index e308d016587..d08434eb1bf 100644
--- a/src/Common/LRUCachePolicy.h
+++ b/src/Common/LRUCachePolicy.h
@@ -22,6 +22,7 @@ class LRUCachePolicy : public ICachePolicy<Key, Mapped, HashFunction, WeightFunc
 public:
     using Base = ICachePolicy<Key, Mapped, HashFunction, WeightFunction>;
     using typename Base::MappedPtr;
+    using typename Base::KeyMapped;
     using typename Base::OnWeightLossFunction;
 
     /** Initialize LRUCachePolicy with max_size_in_bytes and max_entries.
@@ -116,6 +117,14 @@ public:
         removeOverflow();
     }
 
+    std::vector<KeyMapped> dump() const override
+    {
+        std::vector<KeyMapped> res;
+        for (const auto & [key, cell] : cells)
+            res.push_back({key, cell.value});
+        return res;
+    }
+
 protected:
     using LRUQueue = std::list<Key>;
     using LRUQueueIterator = typename LRUQueue::iterator;
diff --git a/src/Common/SLRUCachePolicy.h b/src/Common/SLRUCachePolicy.h
index a568d7f9c7f..42ee9916805 100644
--- a/src/Common/SLRUCachePolicy.h
+++ b/src/Common/SLRUCachePolicy.h
@@ -24,6 +24,7 @@ class SLRUCachePolicy : public ICachePolicy<Key, Mapped, HashFunction, WeightFun
 public:
     using Base = ICachePolicy<Key, Mapped, HashFunction, WeightFunction>;
     using typename Base::MappedPtr;
+    using typename Base::KeyMapped;
     using typename Base::OnWeightLossFunction;
 
     /** Initialize SLRUCachePolicy with max_size_in_bytes and max_protected_size.
@@ -148,6 +149,14 @@ public:
         removeOverflow(probationary_queue, max_size_in_bytes, current_size_in_bytes, /*is_protected=*/false);
     }
 
+    std::vector<KeyMapped> dump() const override
+    {
+        std::vector<KeyMapped> res;
+        for (const auto & [key, cell] : cells)
+            res.push_back({key, cell.value});
+        return res;
+    }
+
 protected:
     using SLRUQueue = std::list<Key>;
     using SLRUQueueIterator = typename SLRUQueue::iterator;