Function PathNameCreateTemporaryFile

src/backend/storage/file/fd.c:1827–1857

* Create a new file. The directory containing it must already exist. Files * created this way are subject to temp_file_limit and are automatically * closed at end of transaction, but are not automatically deleted on close * because they are intended to be shared between cooperating backends. * * If the file is inside the top-level temporary directory, its name should * begin with PG_TEMP_F

 * the prefix isn't needed.
 */
File
PathNameCreateTemporaryFile(const char *path, bool error_on_failure)
{
	File		file;

	ResourceOwnerEnlargeFiles(CurrentResourceOwner);

	/*
	 * Open the file.  Note: we don't use O_EXCL, in case there is an orphaned
	 * temp file that can be reused.
	 */
	file = PathNameOpenFile(path, O_RDWR | O_CREAT | O_TRUNC | PG_BINARY);
	if (file <= 0)
	{
		if (error_on_failure)
			ereport(ERROR,
					(errcode_for_file_access(),
					 errmsg("could not create temporary file \"%s\": %m",
							path)));
		else
			return file;
	}

	/* Mark it for temp_file_limit accounting. */
	VfdCache[file].fdstate |= FD_TEMP_FILE_LIMIT;

	/* Register it for automatic close. */
	RegisterTemporaryFile(file);

	return file;
}

/*
 * Open a file that was created with PathNameCreateTemporaryFile, possibly in