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Fix multiple duckdb instances clash on the same temporary directory. #887

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Fix multiple duckdb instances clash on the same temporary directory. #887

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46 changes: 45 additions & 1 deletion src/pgduckdb_duckdb.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -36,10 +36,48 @@ extern "C" {
#include "nodes/value.h" // strVal
#include "utils/fmgrprotos.h" // pg_sequence_last_value
#include "utils/lsyscache.h" // get_relname_relid
#include "storage/ipc.h" // on_proc_exit
}

namespace pgduckdb {

/*
* Make sure the hook is registered once for a backend.
* This flag is also used to get a unique temporary directory name
* for in-memory duckdb instance, otherwise they clash on the same
* temporary file names. The fix is on pg_duckdb side until
* https://github.com/duckdb/duckdb/issues/15173 is resolved.
*/
static bool set_up_instance_directory_hook = false;

/*
* The length is 37, because a UUID has 36 characters and we need to add a NULL
* byte. The approach is the same as for bgw_session_hint.
*/
static char duckdb_instance_directory[37];
void RemoveTemporaryDirectory(int code = 0, Datum arg = 0);

std::string
GetInstanceTempDir() {
if (!set_up_instance_directory_hook) {
Datum random_uuid = DirectFunctionCall1(gen_random_uuid, 0);
Datum uuid_datum = DirectFunctionCall1(uuid_out, random_uuid);
char *uuid_cstr = DatumGetCString(uuid_datum);
strcpy(duckdb_instance_directory, uuid_cstr);

/* Set up the flag first to avoid re-generating uuid in the hook */
set_up_instance_directory_hook = true;
on_proc_exit(RemoveTemporaryDirectory, 0);
}

return (std::string)duckdb_temporary_directory + "/" + (std::string)duckdb_instance_directory;
}

void
RemoveTemporaryDirectory(int /*code*/, Datum /*arg*/) {
std::filesystem::remove_all(GetInstanceTempDir());
}

const char *
GetSessionHint() {
if (!IsEmptyString(duckdb_motherduck_session_hint)) {
Expand Down Expand Up @@ -96,14 +134,19 @@ DuckDBManager::Initialize() {
std::filesystem::create_directories(duckdb_extension_directory);

duckdb::DBConfig config;

// Special case for temporary directory, that should be unique for every instance
std::string instance_temp_directory = GetInstanceTempDir();
config.options.temporary_directory = instance_temp_directory;
std::filesystem::create_directory(instance_temp_directory);

config.SetOptionByName("custom_user_agent", "pg_duckdb");

SET_DUCKDB_OPTION(allow_unsigned_extensions);
SET_DUCKDB_OPTION(enable_external_access);
SET_DUCKDB_OPTION(allow_community_extensions);
SET_DUCKDB_OPTION(autoinstall_known_extensions);
SET_DUCKDB_OPTION(autoload_known_extensions);
SET_DUCKDB_OPTION(temporary_directory);
SET_DUCKDB_OPTION(extension_directory);

if (duckdb_maximum_memory > 0) {
Expand Down Expand Up @@ -215,6 +258,7 @@ DuckDBManager::Reset() {
delete database;
database = nullptr;
UnclaimBgwSessionHint();
RemoveTemporaryDirectory();
}

int64
Expand Down