On Wed, Jun 09, 2010 at 02:45:18PM +0000, Jens Rehsack wrote: > On 06/09/10 14:36, Tim Bunce wrote: > >> > >>The interface of the per-table API doesn't allow that :( > >>That's exactly the reason why I thought it's required to warn about that. > > > >Can it be expressed as "this is regarded as a bug and is likely to change"? > > It's a bug, it's a bug by design and yes, this is likely to change > (in distant future). > This behavior is listed under "GOTCHAS AND WARNINGS" (which seems to > be Jeffs place for describing "BUGS AND LIMITATIONS".
It would be good to explicitly say it's a bug and it's likely to change. > >>When I took over SQL::Statement and Tux got DBD::CSV, we talked each > >>other and discovered that an per-table API for indices is missing. > >> > >>This is one goal I want to reach when developing SQL::Statement 2.0 - but > >>it will be a long road. > >> > >>>The hash/DBM style databases should be modeled as two column tables > >>>with a unique constraint on the key column. > >> > >>The table-API just knows: fetch_row, push_row, push_names and some > >>optimized routines to allow update/delete specific rows. > > > >Insert could do a fetch_row first and fail if a row is found. > > It couldn't trivialy, because it must do a full table scan for it > and create a subquery which allows to match. And, while this might > be possible for SQL::Statement, I currently have no idea how to do > it for DBI::SQL::Statement. But let me sleep over it (I'm sure I will > find a way). > > >Update could do a fetch_row first and fail if the row is not found. > > This should happen. I try it and report. > > >Apart from the performance hit, what's the problem? > > I rate a full table scan on INSERT not as a minor performance hit. > OTOH it's better to be slow than inconsistent. Sure, but I was thinking specifically of "hash/DBM style databases". It's perfectly understandable (and NOT a bug) that things like CSV files don't support unique constraints. On the other hand, databases built on hashes DO have a unique constraint and silently discarding rows (on inserts) or inserting rows (on updates) is a bug. Tim.
