On Tue, 18 Sep 2012 02:12:18 -0700, Darren Duncan <dar...@darrenduncan.net> wrote:
> Jens Rehsack wrote: > > today I got some people in irc://irc.perl.org/#dbi to discuss planned > > extension to DBD::File. > > > > There were several goals to reach: > > 1) add readonly mode to DBI::DBD::SqlEngine > > ==> will be solved by adding a new attribute sql_readonly to > > DBI::DBD::SqlEngine and if required fix DBI::SQL::Nano and > > SQL::Statement and bump SQL::Statement requirement in *::Nano > > I would recommend doing the complement, backwards-compatibility concerns > aside. > > Make read-only the default behavior and have a new attribute sql_writable > instead. If the goal is to make it possible for safer behavior, that should > be > the default. Then people don't "accidentally" make changes when they didn't > mean to. I would not. That is VERY counter-intuïtive. All (other) DBD's are read-write by default, as it should be. > If backwards-compatibility is the only reason not to do that, you can phase > it > in over time maybe in a similar manner to how strictures were in Perl; eg, if > someone explicitly requires a version number that is greater than X, then > readonly is the default; if they have no explicit version requirement, then > something backwards-compatible is the default. No, read-only support is only added to make implementing streams as data-sources easier. Maybe just for the thought-process, but still. Jens and I talked this through when imagining a file like database.tar.gz being opened using Archive::Tar, which contains many CSV files (the tables). A good example for a read-only data-source. Jens then proclaimed it would probably not bee too hard to extend the API to allow writable streams, which I doubted, but discussion went on. > > 2) add support for other I/O layers to DBD::File > > a) add support for streams (PerlIO) > > b) add support for other kind of fetch_row/push_row processing > > Does the current version work with files in a stream fashion, No, DBD::File *always* uses <c>open</c> to open a data-source. Maybe that is why it is called DBD::File. > such as only reading in enough at a time that it needs, or does it > read the whole file before doing anything? That depends on the implementation in the DBD that extends DBD::File e.g. DBD::CSV reads the complete file at once. > Regardless, streaming is great for scalability. It means you can have > many-gigabyte files and be able to work with them. And security is helped as > it > isn't so easy for someone to DOS you by giving you a huge input. Yes, one of the thoughts we discussed -- H.Merijn Brand http://tux.nl Perl Monger http://amsterdam.pm.org/ using perl5.00307 .. 5.14 porting perl5 on HP-UX, AIX, and openSUSE http://mirrors.develooper.com/hpux/ http://www.test-smoke.org/ http://qa.perl.org http://www.goldmark.org/jeff/stupid-disclaimers/
