[Samba] Samba as a frontend to virtual files
kirk at daycos.com
Thu Jun 15 21:30:18 GMT 2006
My company built a little business application in FoxPro many years ago, and
it's gradually grown into a giant ball of mission-critical haywire. We've
starting porting small parts of it to PostgreSQL, but it will probably take
years to complete the project. In the mean time, I've been considering the
option of hacking Samba to present a set of virtual files that are actually
frontends to PostgreSQL tables.
For those of you who are blissfully unaware of FoxPro's workings, it
basically operates on a bunch of binary files that each client reads from a
fileserver when it wants to search and writes when it wants to update.
These files have a very simple format: a fixed-length header followed by a
number of fixed-length records.
My idea was something like this:
1) Add a "foxproid" column to each PostgreSQL table.
2) When a client seek()s to an offset, convert that to a row number.
3) If the client read()s, do:
a) select * from pgtable where foxproid = $seek_row;
b) Convert the results into a string of bytes (this process is well
defined) and return them to the client.
4) If the client write()s, do:
a) Convert the string of bytes into an array of values (this process is
also well defined).
b) update pgtable set column1=array, etc...
5) If the client asks for a list of files, return the list of eligible
...and so on. The payoff would be that legacy code could still access the
data without realizing that it was running against an RDBMS, but we could
gradually transition to a pure client/server system at our leisure. We're
currently running some home-rolled scripts to convert the table files to
PostgreSQL tables on an hourly basis, but the possibility of doing away
with that architecture and keeping live data in a real database is awfully
attractive. If this worked, I could almost guarantee that every FoxPro
user the the world would immediately migrate to such a setup.
What do you think? Does this seem feasible, or hopelessly out of scope for
Samba's design. Would a good programmer who hasn't had a reason to look at
Samba's codebase before be able to manage such a thing?
The Day Companies
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