Re: Encoding for tables in DBD::File

On 06/01/10 10:42, Tim Bunce wrote:
> On Sun, May 30, 2010 at 12:33:44PM +0200, H.Merijn Brand wrote:
>> In DBI-1.611 I introduced f_encoding for tables. That works great.
>>
>> In 1.611, f_encoding was evaluated from the database handle each time a
>> table (file) was opened, so
>>
>>    my $dbh = DBI->connect ("dbi:File:");
>>
>>    $dbh->{f_encoding} = undef; # raw mode
>>    my $sta = $dbh->prepare ("select * from foo");
>>
>>    $dbh->{f_encoding} = "utf-8"; # Unicode UTF-8
>>    my $stb = $dbh->prepare ("select * from foo");
>>
>> works as this coder would expect: $sta opened table foo in raw mode,
>> whereas $stb open THE SAME table in utf-8 encoding.
>>
>>
>> Now with the rework for DBD::File, the meta-info for a table is stored
>> only once, on first opening of the table. This is to ensure being able
>> to follow ANSI SQL in case preserving/ignoring issues, which IMHO is a
>> good thing.
>>
>> On the one hand, the code in 1.611 could be considered more DWIM than
>> the current state, but on the other, something could be said for the
>> new situation too: it is insane to have two concurrent handles on the
>> same file in two different encodings.
>>
>> OTOH, it is imaginable that when I CLOSE a handle to a table and open
>> it again, now in different encoding, that action is completely legit.
>>
>> That would mean we'd have to change a few innards to enable resetting
>> some previous gained knowledge about tables OR flag a table being
>> closed, and re-evaluate flags like f_encoding when the table is opened
>> again.
>
> [I'm not sure I understand the situation, but ...]
> it seems reasonable for the encoding of a table to be sticky,
> which implies some kind of cache in the $dbh.

Well, I think Merijn wants to point to the situation, that the behaviour
has changed. In DBI 1.611 f_encoding wasn't sticky, in DBI 1.612 it will
be. Maybe he asks indirect about a flag like f_keepoldbehaviour which will
update the f_encoding in the meta data, when it has changed globally?

Jens