atom feed23 messages in org.perl.dbi-devRe: AutoCommit and connect_cached()
FromSent OnAttachments
David WheelerJan 31, 2005 10:28 pm 
Tim BunceFeb 1, 2005 2:43 am 
David WheelerFeb 1, 2005 9:16 am 
Tim BunceFeb 2, 2005 2:58 am 
David WheelerFeb 2, 2005 10:49 am 
David WheelerFeb 2, 2005 10:57 am 
Tim BunceFeb 3, 2005 7:44 am 
David WheelerFeb 3, 2005 8:40 am 
Tim BunceFeb 3, 2005 3:30 pm 
David WheelerFeb 3, 2005 3:48 pm 
Tim BunceFeb 4, 2005 2:07 am 
David WheelerFeb 4, 2005 10:38 am 
Sheikin SergeiFeb 4, 2005 11:31 am 
Michael A ChaseFeb 4, 2005 12:22 pm 
David WheelerFeb 11, 2005 11:18 am 
Tim BunceFeb 12, 2005 10:11 am 
David WheelerFeb 12, 2005 4:35 pm 
Tim BunceFeb 13, 2005 2:44 pm 
David WheelerFeb 13, 2005 5:54 pm 
Tim BunceFeb 14, 2005 3:09 am 
David WheelerFeb 15, 2005 10:37 am 
Tim BunceFeb 15, 2005 2:21 pm 
David WheelerFeb 15, 2005 9:01 pm 
Subject:Re: AutoCommit and connect_cached()
From:David Wheeler (dav@kineticode.com)
Date:Feb 1, 2005 9:16:27 am
List:org.perl.dbi-dev

On Feb 1, 2005, at 2:44 AM, Tim Bunce wrote:

Depends what you mean by wrong. I don't see any 'bugs' here.

No, I wouldn't call it a bug, but it was unexpected behavior (for me, at least).

DBI->connect and connect_cached both explicitly set any supplied attributes plus some implicit defaults like PrintError=1 and AutoCommit=1.

Yes, I figured that. I couldn't figure out how it was doing it, though, looking at the code:

sub connect_cached { my $drh = shift; my ($dsn, $user, $auth, $attr)= @_;

# Needs support at dbh level to clear cache before complaining about # active children. The XS template code does this. Drivers not using # the template must handle clearing the cache themselves. my $cache = $drh->FETCH('CachedKids'); $drh->STORE('CachedKids', $cache = {}) unless $cache;

my @attr_keys = $attr ? sort keys %$attr : (); my $key = join "~~", $dsn, $user||'', $auth||'', $attr ? (@attr_keys,@{$attr}{@attr_keys}) : (); my $dbh = $cache->{$key}; if ($dbh && $dbh->FETCH('Active') && eval { $dbh->ping }) { # XXX warn if BegunWork? # XXX warn if $dbh->FETCH('AutoCommit') != $attr->{AutoCommit} ? # but that's just one (bad) case of a more general issue. return $dbh; } $dbh = $drh->connect(@_); $cache->{$key} = $dbh; # replace prev entry, even if connect failed return $dbh; }

You could certainly argue that connect_cached shouldn't do that. On the other hand, I'd argue that it should perhaps compare the existing and new values and warn if they differ.

I would argue that there should be an attribute to specify whether it does or not (with it doing it by default for the sake of backwards compatibility). I implemented a method like this in my database library:

sub _dbh { DBI->connect_cached(...) }

And I have many different methods within the module that fetch the database handle at different points in a transaction. I think I'd rather not have to cache it some other place every time I start a transaction to be sure that I don't get it from connect_cached again until the transaction is committed or rolled back. I was hoping to just let connect_cached() cache it for me. This is especially tricky when I'm writing tests, where I have setup code that starts a transaction and teardown code that rolls it back. These, obviously, need to exist completely independent of the library that I'm testing.

So how about a NoReset attribute or some such to be passed to connect_cached()?

I think the docs say somewhere that attributes shouldn't be altered when using connect_cached (because you can get this kind of problem). The connect_cached docs need to spell it out though.

Yes, that would help, too. But a new attribute would at allow you to have your cake and let me eat mine, too.

Regards,

David