I was too late to enter this discussion, because have been engaged in
other task, Japanese font. ^_^

I began to see pq from the last day...  First of all, I was surprised these
codes are too small to be expected as Relational database system...  However,
along with proceeding my understanding, I was getting realize hmmm this
is that, the Plan 9 way of dealing with database, everything resources are
named files...

Join could be very easy to Plan 9, yes, agreed.  Indexing could be done this way,
agreed.  Record is considered as a line deliminated by a character, and the
attribute is individual elements enclosed by such delimiters in this line.  The
file can be called 'database'  in a normal sense.  Record lock is file lock, and
we don't need any other mechanism for it, because fileserver can offer it.
Yes, very interesting!

In your implementation, numbers are treated by ascii digit number only?
How about floating point number?
Does it have some arithmetics such as plus, munus, multiple or <, > >=
etc operators?

Sorry, I'm not full understanding of your PQ yet.

Kenji