PostgreSQL overall design

Hi All,

  Can anyone please tell/point  me where I can get the postgresql system layout (I've an interest to contribute). I would also like to know the files involved for performing each task ( for eg when doing a select operation what is exactly happening in postgres along with the files).

  I was wandering inside the source for a while and I couldn't get a start point to go with.

 Need a clarification in copydir.c file of src/port directory,  In the following snippet the destination directory is created first then the source directory is read. Suppose if I don't have permission to read the source, even then the destination directory would be created.
I just want to know whether there is any reason for doing so?

        if (mkdir(todir, S_IRUSR | S_IWUSR | S_IXUSR) != 0)
                ereport(ERROR,
                                (errcode_for_file_access(),
                                 errmsg("could not create directory \"%s\": %m", todir)));

        xldir = AllocateDir(fromdir);
        if (xldir == NULL)
                ereport(ERROR,
                                (errcode_for_file_access(),
                                 errmsg("could not open directory \"%s\": %m", fromdir)));



--
with thanks & regards,
S.Gnanavel
Satyam Computer Services Ltd.