[minor] Add a query statement to clear cache access record

Author: dentiny

src/external_file_cache_stats_recorder.cpp

@@ -114,6 +114,13 @@ void ExternalFileCacheStatsRecorder::UpdateExternalFileCacheWithLock() {
 	});
 }
 
+void ExternalFileCacheStatsRecorder::ClearCacheAccessRecord() {
+	std::lock_guard<std::mutex> lck(mu);
+	cache_access_record.hit_count = 0;
+	cache_access_record.miss_count = 0;
+	cache_access_record.partial_hit_count = 0;
+}
+
 void ExternalFileCacheStatsRecorder::ResetExternalFileCache(ExternalFileCache &cache) {
 	std::lock_guard<std::mutex> lck(mu);
 	external_file_cache = &cache;

src/include/external_file_cache_stats_recorder.hpp

@@ -41,6 +41,9 @@ class ExternalFileCacheStatsRecorder {
 	// Get cache access records.
 	CacheAccessRecord GetCacheAccessRecord() const;
 
+	// Clear cache access record.
+	void ClearCacheAccessRecord();
+
 	// Set external file cache, used to invoke at extension reload where database instance has changed.
 	// TODO(hjiang): Current approach only assumes single external file cache and only supports one dataabase instance.
 	void ResetExternalFileCache(ExternalFileCache &cache);

src/observefs_extension.cpp

@@ -22,6 +22,9 @@ namespace duckdb {
 
 namespace {
 
+// Indicates successful query.
+constexpr bool SUCCESS = true;
+
 // Get database instance from expression state.
 // Returned instance ownership lies in the given [`state`].
 DatabaseInstance &GetDatabaseInstance(ExpressionState &state) {
@@ -76,7 +79,6 @@ void WrapFileSystem(const DataChunk &args, ExpressionState &state, Vector &resul
 	ObservabilityFsRefRegistry::Get().Register(observe_filesystem.get());
 	vfs.RegisterSubSystem(std::move(observe_filesystem));
 
-	constexpr bool SUCCESS = true;
 	result.Reference(Value(SUCCESS));
 }
 
@@ -108,6 +110,11 @@ void ListRegisteredFileSystems(DataChunk &args, ExpressionState &state, Vector &
 	FlatVector::SetValidity(result, ValidityMask(filesystems.size()));
 }
 
+void ClearExternalFileCacheStatsRecord(DataChunk &args, ExpressionState &state, Vector &result) {
+	GetExternalFileCacheStatsRecorder().ClearCacheAccessRecord();
+	result.Reference(Value(SUCCESS));
+}
+
 // Extract or get httpfs filesystem.
 unique_ptr<FileSystem> ExtractOrCreateHttpfs(FileSystem &vfs) {
 	auto filesystems = vfs.ListSubSystems();
@@ -228,6 +235,13 @@ void LoadInternal(ExtensionLoader &loader) {
 	                                              /*return_type=*/LogicalTypeId::BOOLEAN, WrapFileSystem);
 	loader.RegisterFunction(wrap_cache_filesystem_function);
 
+	// Register a function to clear external file cache stats record.
+	ScalarFunction clear_external_file_cache_access_record_function("observefs_clear_external_file_cache_access_record",
+	                                                                /*arguments=*/ {},
+	                                                                /*return_type=*/LogicalTypeId::BOOLEAN,
+	                                                                ClearExternalFileCacheStatsRecord);
+	loader.RegisterFunction(clear_external_file_cache_access_record_function);
+
 	// Register external file cache access query function.
 	loader.RegisterFunction(ExternalFileCacheAccessQueryFunc());
 }

test/sql/external_file_cache_access_record.test

@@ -4,7 +4,10 @@
 
 require observefs
 
-# No results initially.
+# Clear and query initial cache access record.
+statement ok
+SELECT observefs_clear_external_file_cache_access_record();
+
 query III
 SELECT * FROM observefs_external_file_cache_access_record();
 ----