Using python for a CAD program
David Cuthbert
dacut at kanga.org
Sat May 20 03:19:24 EDT 2006
Terry Hancock wrote:
> I disagree that transactions are bad for CAD -- they may have
> a different semantic role and the needed granularity may be
> different, but the need to roll data back to an earlier revision
> is just as present in drawings as it is for code or financial
> transactions.
Sure, but that's called source control. So you do need transactions,
but for the entire database state, not on database operations. (This
was certainly true at Cadence -- there was a thriving third-party market
for handling source control on CDBA databases, and I never encountered
any code which operated on the database in a transactional manner.
OpenAccess did have some basic support for transactions, but I never
heard of anyone using them.)
Some kind of transactionality is needed for undo/redo, but this is
usually done in a different (some might say "more efficient", others
might say "hackier") method than how transactions are implemented for
RDBMS (that I've dealt with, anyway). I suspect this can be attributed
to two major factors: concurrent access is never an issue in such
systems, and the number of database objects representing a given state
is far larger than in, say, e-commerce.
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