Function TempTablespacePath

src/backend/storage/file/fd.c:1722–1740

* Return the path of the temp directory in a given tablespace. */

 * Return the path of the temp directory in a given tablespace.
 */
void
TempTablespacePath(char *path, Oid tablespace)
{
	/*
	 * Identify the tempfile directory for this tablespace.
	 *
	 * If someone tries to specify pg_global, use pg_default instead.
	 */
	if (tablespace == InvalidOid ||
		tablespace == DEFAULTTABLESPACE_OID ||
		tablespace == GLOBALTABLESPACE_OID)
		snprintf(path, MAXPGPATH, "base/%s", PG_TEMP_FILES_DIR);
	else
	{
		/* All other tablespaces are accessed via symlinks */
		snprintf(path, MAXPGPATH, "pg_tblspc/%u/%s/%s",
				 tablespace, GP_TABLESPACE_VERSION_DIRECTORY, PG_TEMP_FILES_DIR);
	}
}

/*
 * Open a temporary file in a specific tablespace.