On 12.12.12 20:34, H.Merijn Brand wrote:
On Wed, 12 Dec 2012 16:31:44 +0100, Jens Rehsack <rehs...@cpan.org>
wrote:
On 01.12.12 23:14, Tim Bunce wrote:
On Thu, Nov 29, 2012 at 10:15:19PM +0100, Jens Rehsack wrote:
But back to the issue - now it seems dbm_tables is fetched earlier
in some cases than f_dir which causes an invocation of
DBI::DBD::SqlEngine::Table::get_table_meta (including
DBI::DBD::SqlEngine::Table::bootstrap_table_meta) before f_dir
has been set. This causes $dbh->{sql_meta}->{fred}->{f_dir} being
initialized to the default value of $dbh->{f_dir} which is
always cur_dir().
Looking into DBI::DBD::SqlEngine::dr::connect around line 180
it could be seen that there's already some magic for "some
settings must be done before others".
A quick fix for "now" could be: keys: ("sql_meta", $dbh->{dbm_meta},
...) must be initialized last - after any other k/v pair from %$attrs.
Another quick should could be forbid setting meta info during connect(),
as it's documented - but this would be a hugh step backwards in my
effort making DBI::DBD::SqlEngine and derived DBD's usable through
Gofer proxy. So I'd prefer the first quick shot ...
For longer way, I'd like to refactor the order procedure to a
more flexible way:
$dbh->{dbd_init_order} = [
[qw(Profile RaiseError PrintError AutoCommit)],
[qw(ReadOnly ...)],
...
[qw(sql_meta dbm_tables ...)]
];
Remaining question in that proposal: where's the fence between "must
be last" and "insert unnamed attrs here"?
I don't know, but I would like a working DBI for 5.17.6+ before too long.
Well, we developed two patches for now:
1) Merijn's patch - http://pasta.test-smoke.org/385
+ looks simple, easy to understand
+ easy to extend
+ easy to override
This is a good and bad point in once: easy to override allows
easy modifying the order, but it allows modifying the order
easily ;) This can cause in hard to debug errors like we got
one in RT#81516. And put a warning on it: use only if you
completely understood DBI::DBD::SqlEngine and DBD::File internals
is similar to: "don't do"
+ one single point of maintenance
Which ignores the design of DBI::DBD::SqlEngine which forces
a separate place for those kind of initializations:
DBD::Your_Drv::db::init_default_attributes.
- makes assumptions about attribute names of derived DBD's
(e.g. dbm_tables, but this can be easily renamed by assigning
new name for it to $dbh->{dbm_meta} (by driver author), eg.
$dbh->{dbm_meta} = "dbm_sources")
which makes me/us/you want more documentation about what DBI/DBD
guarantees, expects, supports etc. there is no real "you should do
this" or "this is officially off-bound"
Did you read DBD::File::Developers (and DBI::DBD::SqlEngine::Developers)?
I agree, those documents need to be extended, but many of the
things I tell are described there.
- increases complexitiy when more issues came up with similar
patterns (eg. /_meta$/ can't be set from outside, but from
derived driver)
but still offers easy documentation for every single entry
2) Jens' patch - http://pasta.test-smoke.org/387
+ backward compatible to ancient attributes (csv_file, csv_ext, ...)
though I value this point, we are talking about DBD's we all
control. The newest DBD::CSV and DBD::DBM will require the new DBI
so conflicts are not likely to happen. To be honest, I - as
maintainer of DBD::CSV - didn't even know csv_file was still
supported
My fault, I thought it would. But DBD::File supports dbm_ext (aliases
f_ext) as well as dbm_lockfile (aliases f_lockfile). I'm pretty sure,
DBD::AnyData (greetings to Sven Doweit) will have similar surprises.
+ no assumptions on derived DBD's
a very good point
+ no false positives on pattern match
if everything is well-documented, then false positives should not
happen or better cause havoc
- more complicated for quick review
can be solved by well-chosen inline docs
- This patch will probably need to have extra code in (many) other
places, which my patch tried to avoid
I wouldn't expect - I see only one extra point which is in DBD::File
to enable backward compatibility to DBD::File 0.40 for at least
developers (aliasing f_meta to sql_meta). Skipping this, even DBD::File
needs no extra code.
To value your comments, I've reworked my patch a little bit to allow
easier modifying in sub-classes (derived DBD's).
You can find it at http://pasta.test-smoke.org/389
Any other +/- comments?
Yes please, don't feel shy!
Tell us!
In general both versions would fix the root cause of RT#81516,
while the maintainers (Merijn, me) cannot choose the right one.
What he said
Jens
/o\
Jens
