Local object cache for cached_httpfs extension

* To cache remote object, user need to explicilty use
  `duckdb.cache(path)` function. Caching will not be triggered on normal
  `SELECT` queries.

* When file is currently being cached and if we run in parallel another
  query targeting same remote object - second query will fail because it
  will not be able to take read lock.

* PG_DATADIR/duckdb_cache will be used as cache directory

Makefile

@@ -19,6 +19,7 @@ SRCS = src/scan/heap_reader.cpp \
 	   src/pgduckdb_options.cpp \
 	   src/pgduckdb_planner.cpp \
 	   src/pgduckdb_types.cpp \
+	   src/pgduckdb_utils.cpp \
 	   src/pgduckdb.cpp
 
 OBJS = $(subst .cpp,.o, $(SRCS))

include/pgduckdb/pgduckdb_options.hpp

@@ -1,40 +1,19 @@
 #pragma once
 
+#include "duckdb.hpp"
+
 #include <string>
 #include <vector>
 
 namespace pgduckdb {
 
-/* constants for duckdb.secrets */
-#define Natts_duckdb_secret              6
-#define Anum_duckdb_secret_type          1
-#define Anum_duckdb_secret_id            2
-#define Anum_duckdb_secret_secret        3
-#define Anum_duckdb_secret_region        4
-#define Anum_duckdb_secret_endpoint      5
-#define Anum_duckdb_secret_r2_account_id 6
-
-typedef struct DuckdbSecret {
-	std::string type;
-	std::string id;
-	std::string secret;
-	std::string region;
-	std::string endpoint;
-	std::string r2_account_id;
-} DuckdbSecret;
-
-extern std::vector<DuckdbSecret> ReadDuckdbSecrets();
-
-/* constants for duckdb.extensions */
-#define Natts_duckdb_extension       2
-#define Anum_duckdb_extension_name   1
-#define Anum_duckdb_extension_enable 2
+void AddSecretsToDuckdbContext(duckdb::ClientContext &context);
 
-typedef struct DuckdbExension {
+typedef struct DuckdbExtension {
 	std::string name;
 	bool enabled;
-} DuckdbExension;
+} DuckdbExtension;
 
-extern std::vector<DuckdbExension> ReadDuckdbExtensions();
+extern std::vector<DuckdbExtension> ReadDuckdbExtensions();
 
 } // namespace pgduckdb

include/pgduckdb/pgduckdb_utils.hpp

@@ -19,4 +19,8 @@ TokenizeString(char *str, const char delimiter) {
 	return v;
 };
 
+std::string CreateOrGetDirectoryPath(std::string directoryName);
+
 } // namespace pgduckdb
+
+void DuckdbCreateCacheDirectory(void);

sql/pg_duckdb--0.0.1.sql

@@ -75,6 +75,9 @@ CREATE TABLE extensions (
 CREATE OR REPLACE FUNCTION install_extension(extension_name TEXT) RETURNS bool
     LANGUAGE C AS 'MODULE_PATHNAME', 'install_extension';
 
+CREATE OR REPLACE FUNCTION cache(path TEXT) RETURNS bool
+    LANGUAGE C AS 'MODULE_PATHNAME', 'cache';
+
 DO $$
 BEGIN
     RAISE WARNING 'To actually execute queries using DuckDB you need to run "SET duckdb.execution TO true;"';

src/pgduckdb.cpp

@@ -18,6 +18,7 @@ PG_MODULE_MAGIC;
 void
 _PG_init(void) {
 	DuckdbInitGUC();
+	DuckdbCreateCacheDirectory();
 	DuckdbInitHooks();
 	DuckdbInitNode();
 }

src/pgduckdb_duckdb.cpp

@@ -9,64 +9,11 @@
 #include "pgduckdb/scan/postgres_seq_scan.hpp"
 #include "pgduckdb/pgduckdb_utils.hpp"
 
-#include <string>
-
-#include <sys/types.h>
-#include <sys/stat.h>
-#include <unistd.h>
-#include <errno.h>
-
 namespace pgduckdb {
-
-static bool
-CheckDataDirectory(const char *data_directory) {
-	struct stat info;
-
-	if (lstat(data_directory, &info) != 0) {
-		if (errno == ENOENT) {
-			elog(DEBUG2, "Directory `%s` doesn't exists.", data_directory);
-			return false;
-		} else if (errno == EACCES) {
-			elog(ERROR, "Can't access `%s` directory.", data_directory);
-		} else {
-			elog(ERROR, "Other error when reading `%s`.", data_directory);
-		}
-	}
-
-	if (!S_ISDIR(info.st_mode)) {
-		elog(WARNING, "`%s` is not directory.", data_directory);
-	}
-
-	if (access(data_directory, R_OK | W_OK)) {
-		elog(ERROR, "Directory `%s` permission problem.", data_directory);
-	}
-
-	return true;
-}
-
-static std::string
-GetExtensionDirectory() {
-	StringInfo duckdb_extension_data_directory = makeStringInfo();
-	appendStringInfo(duckdb_extension_data_directory, "%s/duckdb_extensions", DataDir);
-
-	if (!CheckDataDirectory(duckdb_extension_data_directory->data)) {
-		if (mkdir(duckdb_extension_data_directory->data, S_IRWXU | S_IRWXG | S_IRWXO) == -1) {
-			int error = errno;
-			pfree(duckdb_extension_data_directory->data);
-			elog(ERROR, "Creating duckdb extensions directory failed with reason `%s`\n", strerror(error));
-		}
-		elog(DEBUG2, "Created %s as `duckdb.data_dir`", duckdb_extension_data_directory->data);
-	};
-
-	std::string duckdb_extension_directory(duckdb_extension_data_directory->data);
-	pfree(duckdb_extension_data_directory->data);
-	return duckdb_extension_directory;
-}
-
 duckdb::unique_ptr<duckdb::DuckDB>
 DuckdbOpenDatabase() {
 	duckdb::DBConfig config;
-	config.SetOptionByName("extension_directory", GetExtensionDirectory());
+	config.SetOptionByName("extension_directory", CreateOrGetDirectoryPath("duckdb_extensions"));
 	return duckdb::make_uniq<duckdb::DuckDB>(nullptr, &config);
 }
 
@@ -99,29 +46,7 @@ DuckdbCreateConnection(List *rtables, PlannerInfo *planner_info, List *needed_co
 	catalog.CreateTableFunction(context, &index_scan_info);
 	context.transaction.Commit();
 
-	auto duckdb_secrets = ReadDuckdbSecrets();
-
-	int secret_id = 0;
-	for (auto &secret : duckdb_secrets) {
-		StringInfo secret_key = makeStringInfo();
-		bool is_r2_cloud_secret = (secret.type.rfind("R2", 0) == 0);
-		appendStringInfo(secret_key, "CREATE SECRET duckdbSecret_%d ", secret_id);
-		appendStringInfo(secret_key, "(TYPE %s, KEY_ID '%s', SECRET '%s'", secret.type.c_str(), secret.id.c_str(),
-		                 secret.secret.c_str());
-		if (secret.region.length() && !is_r2_cloud_secret) {
-			appendStringInfo(secret_key, ", REGION '%s'", secret.region.c_str());
-		}
-		if (secret.endpoint.length() && !is_r2_cloud_secret) {
-			appendStringInfo(secret_key, ", ENDPOINT '%s'", secret.endpoint.c_str());
-		}
-		if (is_r2_cloud_secret) {
-			appendStringInfo(secret_key, ", ACCOUNT_ID '%s'", secret.endpoint.c_str());
-		}
-		appendStringInfo(secret_key, ");");
-		context.Query(secret_key->data, false);
-		pfree(secret_key->data);
-		secret_id++;
-	}
+	AddSecretsToDuckdbContext(context);
 
 	auto duckdb_extensions = ReadDuckdbExtensions();
 
@@ -137,6 +62,10 @@ DuckdbCreateConnection(List *rtables, PlannerInfo *planner_info, List *needed_co
 		pfree(duckdb_extension->data);
 	}
 
+	auto http_file_cache_set_dir_query =
+	    duckdb::StringUtil::Format("SET http_file_cache_dir TO '%s';", CreateOrGetDirectoryPath("duckdb_cache"));
+	context.Query(http_file_cache_set_dir_query, false);
+
 	return connection;
 }
 

src/pgduckdb_options.cpp

@@ -16,9 +16,33 @@ extern "C" {
 
 #include "pgduckdb/pgduckdb_options.hpp"
 #include "pgduckdb/pgduckdb_duckdb.hpp"
+#include "pgduckdb/pgduckdb_utils.hpp"
 
 namespace pgduckdb {
 
+/* constants for duckdb.secrets */
+#define Natts_duckdb_secret              6
+#define Anum_duckdb_secret_type          1
+#define Anum_duckdb_secret_id            2
+#define Anum_duckdb_secret_secret        3
+#define Anum_duckdb_secret_region        4
+#define Anum_duckdb_secret_endpoint      5
+#define Anum_duckdb_secret_r2_account_id 6
+
+typedef struct DuckdbSecret {
+	std::string type;
+	std::string id;
+	std::string secret;
+	std::string region;
+	std::string endpoint;
+	std::string r2_account_id;
+} DuckdbSecret;
+
+/* constants for duckdb.extensions */
+#define Natts_duckdb_extension       2
+#define Anum_duckdb_extension_name   1
+#define Anum_duckdb_extension_enable 2
+
 static Oid
 GetDuckdbNamespace(void) {
 	return get_namespace_oid("duckdb", false);
@@ -43,8 +67,8 @@ DatumToString(Datum datum) {
 	return column_value;
 }
 
-std::vector<DuckdbSecret>
-ReadDuckdbSecrets() {
+static std::vector<DuckdbSecret>
+DuckdbReadSecrets() {
 	HeapTuple tuple = NULL;
 	Oid duckdb_secret_table_relation_id = SecretsTableRelationId();
 	Relation duckdb_secret_relation = table_open(duckdb_secret_table_relation_id, AccessShareLock);
@@ -79,21 +103,47 @@ ReadDuckdbSecrets() {
 	return duckdb_secrets;
 }
 
-std::vector<DuckdbExension>
+void
+AddSecretsToDuckdbContext(duckdb::ClientContext &context) {
+	auto duckdb_secrets = DuckdbReadSecrets();
+	int secret_id = 0;
+	for (auto &secret : duckdb_secrets) {
+		StringInfo secret_key = makeStringInfo();
+		bool is_r2_cloud_secret = (secret.type.rfind("R2", 0) == 0);
+		appendStringInfo(secret_key, "CREATE SECRET pg_duckdb_secret_%d ", secret_id);
+		appendStringInfo(secret_key, "(TYPE %s, KEY_ID '%s', SECRET '%s'", secret.type.c_str(), secret.id.c_str(),
+		                 secret.secret.c_str());
+		if (secret.region.length() && !is_r2_cloud_secret) {
+			appendStringInfo(secret_key, ", REGION '%s'", secret.region.c_str());
+		}
+		if (secret.endpoint.length() && !is_r2_cloud_secret) {
+			appendStringInfo(secret_key, ", ENDPOINT '%s'", secret.endpoint.c_str());
+		}
+		if (is_r2_cloud_secret) {
+			appendStringInfo(secret_key, ", ACCOUNT_ID '%s'", secret.endpoint.c_str());
+		}
+		appendStringInfo(secret_key, ");");
+		context.Query(secret_key->data, false);
+		pfree(secret_key->data);
+		secret_id++;
+	}
+}
+
+std::vector<DuckdbExtension>
 ReadDuckdbExtensions() {
 	HeapTuple tuple = NULL;
 	Oid duckdb_extension_table_relation_id = ExtensionsTableRelationId();
 	Relation duckdb_extension_relation = table_open(duckdb_extension_table_relation_id, AccessShareLock);
 	SysScanDescData *scan =
 	    systable_beginscan(duckdb_extension_relation, InvalidOid, false, GetActiveSnapshot(), 0, NULL);
-	std::vector<DuckdbExension> duckdb_extensions;
+	std::vector<DuckdbExtension> duckdb_extensions;
 
 	while (HeapTupleIsValid(tuple = systable_getnext(scan))) {
 		Datum datum_array[Natts_duckdb_secret];
 		bool is_null_array[Natts_duckdb_secret];
 
 		heap_deform_tuple(tuple, RelationGetDescr(duckdb_extension_relation), datum_array, is_null_array);
-		DuckdbExension secret;
+		DuckdbExtension secret;
 
 		secret.name = DatumToString(datum_array[Anum_duckdb_extension_name - 1]);
 		secret.enabled = DatumGetBool(datum_array[Anum_duckdb_extension_enable - 1]);
@@ -112,16 +162,11 @@ DuckdbInstallExtension(Datum name) {
 	auto &context = *connection->context;
 
 	auto extension_name = DatumToString(name);
-
-	StringInfo install_extension_command = makeStringInfo();
-	appendStringInfo(install_extension_command, "INSTALL %s;", extension_name.c_str());
-
-	auto res = context.Query(install_extension_command->data, false);
-
-	pfree(install_extension_command->data);
+	auto install_extension_command = duckdb::StringUtil::Format("INSTALL %s;", extension_name.c_str());
+	auto res = context.Query(install_extension_command, false);
 
 	if (res->HasError()) {
-		elog(WARNING, "(duckdb_install_extension) %s", res->GetError().c_str());
+		elog(WARNING, "(DuckdbInstallExtension) %s", res->GetError().c_str());
 		return false;
 	}
 
@@ -145,6 +190,31 @@ DuckdbInstallExtension(Datum name) {
 	return true;
 }
 
+static bool
+DuckdbCacheObject(Datum object) {
+	auto db = DuckdbOpenDatabase();
+	auto connection = duckdb::make_uniq<duckdb::Connection>(*db);
+	auto &context = *connection->context;
+
+	context.Query("SET enable_http_file_cache TO true;", false);
+	auto http_file_cache_set_dir_query =
+	    duckdb::StringUtil::Format("SET http_file_cache_dir TO '%s';", CreateOrGetDirectoryPath("duckdb_cache"));
+	context.Query(http_file_cache_set_dir_query, false);
+
+	AddSecretsToDuckdbContext(context);
+
+	auto object_name = DatumToString(object);
+	auto cache_object_query = duckdb::StringUtil::Format("SELECT 1 FROM '%s';", object_name.c_str());
+	auto res = context.Query(cache_object_query, false);
+
+	if (res->HasError()) {
+		elog(WARNING, "(DuckdbCacheObject) %s", res->GetError().c_str());
+		return false;
+	}
+
+	return true;
+}
+
 } // namespace pgduckdb
 
 extern "C" {
@@ -157,4 +227,12 @@ install_extension(PG_FUNCTION_ARGS) {
 	PG_RETURN_BOOL(result);
 }
 
+PG_FUNCTION_INFO_V1(cache);
+Datum
+cache(PG_FUNCTION_ARGS) {
+	Datum object = PG_GETARG_DATUM(0);
+	bool result = pgduckdb::DuckdbCacheObject(object);
+	PG_RETURN_BOOL(result);
+}
+
 } // extern "C"