Protect catalog change for high throughput (#121)

Author: richard-epsilla

engine/db/catalog/basic_meta_impl.cpp

@@ -263,6 +263,7 @@ Status BasicMetaImpl::LoadDatabase(const std::string& db_catalog_path, const std
   }
 
   databases_[db_name] = db_schema;
+  db_mutexes_[db_name]; // Initializes a mutex for the new database
   loaded_databases_paths_.insert(db_catalog_path);
 
   return Status::OK();
@@ -304,6 +305,7 @@ Status BasicMetaImpl::DropDatabase(const std::string& db_name) {
   }
   loaded_databases_paths_.erase(path);
   databases_.erase(db_name);
+  db_mutexes_.erase(db_name); // Remove mutex for the dropped database
   return Status::OK();
 }
 
@@ -445,6 +447,7 @@ Status ValidateSchema(TableSchema& table_schema, std::vector<EmbeddingModel> &em
 }
 
 Status BasicMetaImpl::CreateTable(const std::string& db_name, TableSchema& table_schema, size_t& table_id) {
+  std::lock_guard<std::mutex> lock(db_mutexes_[db_name]); // Acquire lock for this database
   // Table name cannot be duplicated.
   bool has_table = false;
   auto status = HasTable(db_name, table_schema.name_, has_table);
@@ -519,6 +522,7 @@ Status BasicMetaImpl::GetTable(const std::string& db_name, const std::string& ta
 }
 
 Status BasicMetaImpl::DropTable(const std::string& db_name, const std::string& table_name) {
+  std::lock_guard<std::mutex> lock(db_mutexes_[db_name]); // Acquire lock for this database
   auto it = databases_.find(db_name);
   if (it == databases_.end()) {
     return Status(DB_NOT_FOUND, "Database not found: " + db_name);

engine/db/catalog/basic_meta_impl.hpp

@@ -4,7 +4,7 @@
 #include <atomic>
 #include <unordered_map>
 #include <unordered_set>
-
+#include <mutex>
 #include "db/catalog/meta.hpp"
 #include "services/embedding_service.hpp"
 
@@ -42,6 +42,7 @@ class BasicMetaImpl : public Meta {
   void InjectEmbeddingService(std::shared_ptr<vectordb::engine::EmbeddingService> embedding_service) override;
 
  private:
+  std::unordered_map<std::string, std::mutex> db_mutexes_; // Map to hold a mutex for each database
   std::unordered_map<std::string, DatabaseSchema> databases_;
   std::unordered_set<std::string> loaded_databases_paths_;  // We cannot allow loading the same database twice
   // If the segment is leader (handle sync to storage) or follower (passively sync from storage)