From: Adam Kupczyk <akupczyk@ibm.com>
Date: Tue, 1 Jul 2025 11:23:28 +0000 (+0000)
Subject: kv/KeyValueDB: New estimate_range_size function
X-Git-Tag: v21.0.1~9^2~3
X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=77af5b004e96161e719048cb73ad39e3115895cd;p=ceph.git

kv/KeyValueDB: New estimate_range_size function

Taking estimate_prefix_size to another level.
Makes possible detailed inspection of db size.
Used primarily for bisecting key range.

Signed-off-by: Adam Kupczyk <akupczyk@ibm.com>
---

diff --git a/src/kv/KeyValueDB.h b/src/kv/KeyValueDB.h
index 68f07394eaa..0583107cf50 100644
--- a/src/kv/KeyValueDB.h
+++ b/src/kv/KeyValueDB.h
@@ -410,6 +410,13 @@ public:
 				       const std::string& key_prefix) {
     return 0;
   }
+  /// estimate space utilization for a specified range (in bytes)
+  virtual int64_t estimate_range_size(
+    const std::string& prefix,
+    const std::string& key_from,
+    const std::string& key_to) {
+      return 0;
+  };
 
   /// compact the underlying store
   virtual void compact() {}
diff --git a/src/kv/RocksDBStore.cc b/src/kv/RocksDBStore.cc
index 97830201269..a51968b7036 100644
--- a/src/kv/RocksDBStore.cc
+++ b/src/kv/RocksDBStore.cc
@@ -1433,6 +1433,36 @@ int64_t RocksDBStore::estimate_prefix_size(const string& prefix,
   return size;
 }
 
+int64_t RocksDBStore::estimate_range_size(
+  const string& prefix,
+  const string& key_from,
+  const string& key_to)
+{
+  // The default mode is to derive estimates based on
+  // sst files alone (INCLUDE_FILES).
+  // This gives an irritating result when a batch of keys is
+  // just commited but estimate keeps showing 0.
+  rocksdb::DB::SizeApproximationFlags flags(
+    rocksdb::DB::SizeApproximationFlags::INCLUDE_FILES |
+    rocksdb::DB::SizeApproximationFlags::INCLUDE_MEMTABLES);
+  uint64_t size = 0;
+  auto p_iter = cf_handles.find(prefix);
+  if (p_iter != cf_handles.end()) {
+    for (const auto cf : p_iter->second.handles) {
+      uint64_t s = 0;
+      rocksdb::Range r(key_from, key_to);
+      db->GetApproximateSizes(cf, &r, 1, &s, flags);
+      size += s;
+    }
+  } else {
+    string start = combine_strings(prefix , key_from);
+    string limit = combine_strings(prefix , key_to);
+    rocksdb::Range r(start, limit);
+    db->GetApproximateSizes(default_cf, &r, 1, &size, flags);
+  }
+  return size;
+}
+
 void RocksDBStore::get_statistics(Formatter *f)
 {
   if (!cct->_conf->rocksdb_perf)  {
diff --git a/src/kv/RocksDBStore.h b/src/kv/RocksDBStore.h
index c0cab4cfbcf..a32cc71b0c8 100644
--- a/src/kv/RocksDBStore.h
+++ b/src/kv/RocksDBStore.h
@@ -291,6 +291,9 @@ public:
 
   int64_t estimate_prefix_size(const std::string& prefix,
 			       const std::string& key_prefix) override;
+  int64_t estimate_range_size(const std::string& prefix,
+                              const std::string& key_from,
+                              const std::string& key_to) override;
   struct RocksWBHandler;
   class RocksDBTransactionImpl : public KeyValueDB::TransactionImpl {
   public: