Re: [GENERAL] Perl and AutoCommit
On Sun, 27 Mar 2005 01:34:23 -0500, Madison Kelly <[EMAIL PROTECTED]> wrote:
> Dan Sugalski wrote:
>> At 12:31 AM -0500 3/27/05, Madison Kelly wrote:
>>> What I am trying to do is turn off autocommit for one particular
>>> task in my program. I realize I can turn off AutoCommit when I connect
>>> to the database but in this case that is not what I want to do. This
>>> is a one-off task.
>>
>> Set the AutoCommit attribute of the database handle. Pull up the docs
>> for DBI and search for the "Database Handle Attributes" section.
>
> Hmm... I've read that now (thank you!) and I have added:
>
> $acw=$DB->{AutoCommit};
> print " |- AutoCommit was: [$acw]\n";
> $DB->{AutoCommit} = 0 || die...
> $acn=$DB->{AutoCommit};
> print " |- AutoCommit now: [$acw]\n";
Or maybe:
print " |- AutoCommit now: [$acn]\n";
-^
(Minor typo, may not be relevant).
Frank McKenney
Frank McKenney, McKenney Associates
Richmond, Virginia / (804) 320-4887
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Re: [GENERAL] Perl and AutoCommit
-BEGIN PGP SIGNED MESSAGE-
Hash: SHA1
> $DB->{AutoCommit} = 0 || die...
As someone pointed out, this always dies. In general, you don't
need (or want) to test the results of setting a variable. Also be
aware that in this case you probably want "or" and not "|" - the former
tests the result of "$DB->{AutoCommit} = 0", while the latter actually
tries to set $DB->{AutoCommit} to first "0" and then to the result
of "die". What you want is really
($DB->{AutoCommit} = 0) || die;
which is the same thing, and better written as:
$DB->{AutoCommit} = 0 or die;
Best of all is just to remove the line entirely, as there is no point in
testing the assignment: simply view the contents afterwards:
$DB->{AutoCommit} = 0;
print " |- AutoCommit now: $DB->{AutoCommit}\n";
Also be aware that for DBD::Pg, the following is a known bug
(will be fixed in the upcoming 1.41 release):
> $DB->commit() || die...
In some circumstances commit() returns false when it should return true
(even though it still committed). If you find that happening, simply change
it to $DB->commit(); and trust that the correct thing is indeed happening.
- --
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Re: [GENERAL] Perl and AutoCommit
On Sun, 2005-03-27 at 00:31 -0500, Madison Kelly wrote:
>What I thought would work was:
>
> $DB->begin_work() || die...
> # a lot of transactions
> $DB->commit() || die...
>
maybe a more complete testcase would be in order.
[EMAIL PROTECTED]:~/test $ cat trans.pl
use DBI;
our $dbh = DBI->connect('dbi:Pg:dbname=test') or die 'no database';
$dbh->do('create table transtest(a text)');
$dbh->begin_work() or die 'error in begin';
$dbh->do("insert into transtest values ('foo')");
$dbh->do("insert into transtest values ('bar')");
$dbh->commit() or die 'error in commit' ;
system("psql -d test -c 'select * from transtest;'")
[EMAIL PROTECTED]:~/test $ perl trans.pl
a
-
foo
bar
(2 rows)
[EMAIL PROTECTED]:~/test $
[EMAIL PROTECTED]:~/test $ perl -v
This is perl, v5.8.4 built for x86_64-linux-thread-multi
[EMAIL PROTECTED]:~/test $ perl -MDBI -le 'print $DBI::VERSION'
1.42
[EMAIL PROTECTED]:~/test $
perhaps a database operation is failing between your begin_work()
and your commit() ?
gnari
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Re: [GENERAL] Perl and AutoCommit
At 1:34 AM -0500 3/27/05, Madison Kelly wrote:
Dan Sugalski wrote:
At 12:31 AM -0500 3/27/05, Madison Kelly wrote:
Hi all,
After looking at the postres and perl docs plus some Googling I
can't seem to find the answer I am looking for. I hope maybe
someone here can help. ^_^
What I am trying to do is turn off autocommit for one particular
task in my program. I realize I can turn off AutoCommit when I
connect to the database but in this case that is not what I want
to do. This is a one-off task.
Set the AutoCommit attribute of the database handle. Pull up the
docs for DBI and search for the "Database Handle Attributes"
section.
Hmm... I've read that now (thank you!) and I have added:
$acw=$DB->{AutoCommit};
print " |- AutoCommit was: [$acw]\n";
$DB->{AutoCommit} = 0 || die...
$acn=$DB->{AutoCommit};
print " |- AutoCommit now: [$acw]\n";
$DB->begin_work() || die...
#lot of transactions
$DB->commit() || die...
For some reason though my program dies on the '$DB->{AutoCommit}=0 ...' line.
Well.. yeah. Assignment's an expression, with a value of the right
hand side of the expression. Since the assignment part of the logical
or is false, the right hand side's evaluated and you die, not because
anything failed.
The docs say it's a fatal error to use an unsupported value, so I'd
assume it actually dies and you'd need to trap with eval.
--
Dan
--it's like this---
Dan Sugalski even samurai
[EMAIL PROTECTED] have teddy bears and even
teddy bears get drunk
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Re: [GENERAL] Perl and AutoCommit
Dan Sugalski wrote:
At 12:31 AM -0500 3/27/05, Madison Kelly wrote:
Hi all,
After looking at the postres and perl docs plus some Googling I
can't seem to find the answer I am looking for. I hope maybe someone
here can help. ^_^
What I am trying to do is turn off autocommit for one particular
task in my program. I realize I can turn off AutoCommit when I connect
to the database but in this case that is not what I want to do. This
is a one-off task.
Set the AutoCommit attribute of the database handle. Pull up the docs
for DBI and search for the "Database Handle Attributes" section.
Hmm... I've read that now (thank you!) and I have added:
$acw=$DB->{AutoCommit};
print " |- AutoCommit was: [$acw]\n";
$DB->{AutoCommit} = 0 || die...
$acn=$DB->{AutoCommit};
print " |- AutoCommit now: [$acw]\n";
$DB->begin_work() || die...
#lot of transactions
$DB->commit() || die...
For some reason though my program dies on the '$DB->{AutoCommit}=0 ...'
line. I usually print '$DBI::errstr' in the 'die' to see what happened
but that is blank. I read in that section that some databases simply
don't support turning off AC and will die with a fatal error if you try
to turn it off. Could this be what is happening? If so, shouldn't there
be a more verbose error? Also, I know pgSQL supports AC being turned off
because I first read about this feature in there docs. Am I making an
mistake?
Many thanks!
Madison
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http://tle-bu.thelinuxexperience.com
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Re: [GENERAL] Perl and AutoCommit
Madison Kelly wrote: > >What I am trying to do is turn off autocommit for one particular task > in my program. I realize I can turn off AutoCommit when I connect to the > database but in this case that is not what I want to do. This is a > one-off task. > >What I thought would work was: > > $DB->begin_work() || die... > # a lot of transactions > $DB->commit() || die... > >But that doesn't seem to be it, either... The way I read the postgres docs, there is no autocommit. Every sql command is wrapped in a transaction, unless you issue a "BEGIN" (or "START TRANSACTION"). What makes you think that the code above did not work? What Perl library are you using? What does $DB->begin_work() actually do? --I'm thinking there could be a $DB->begin_transaction() You could turn on some trace output in the postgres server (i.e. postmaster), and observe the sequence of SQL that is being sent. HTH. --yanni ---(end of broadcast)--- TIP 4: Don't 'kill -9' the postmaster
Re: [GENERAL] Perl and AutoCommit
At 12:31 AM -0500 3/27/05, Madison Kelly wrote: Hi all, After looking at the postres and perl docs plus some Googling I can't seem to find the answer I am looking for. I hope maybe someone here can help. ^_^ What I am trying to do is turn off autocommit for one particular task in my program. I realize I can turn off AutoCommit when I connect to the database but in this case that is not what I want to do. This is a one-off task. Set the AutoCommit attribute of the database handle. Pull up the docs for DBI and search for the "Database Handle Attributes" section. -- Dan --it's like this--- Dan Sugalski even samurai [EMAIL PROTECTED] have teddy bears and even teddy bears get drunk ---(end of broadcast)--- TIP 2: you can get off all lists at once with the unregister command (send "unregister YourEmailAddressHere" to [EMAIL PROTECTED])
[GENERAL] Perl and AutoCommit
Hi all, After looking at the postres and perl docs plus some Googling I can't seem to find the answer I am looking for. I hope maybe someone here can help. ^_^ What I am trying to do is turn off autocommit for one particular task in my program. I realize I can turn off AutoCommit when I connect to the database but in this case that is not what I want to do. This is a one-off task. What I thought would work was: $DB->begin_work() || die... # a lot of transactions $DB->commit() || die... But that doesn't seem to be it, either... Any advice would be much appreciated. Even if it's just a pointer to the right docs with the answer that I probably missed while searching. :) Madison -- -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Madison Kelly (Digimer) TLE-BU, The Linux Experience; Back Up http://tle-bu.thelinuxexperience.com -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- ---(end of broadcast)--- TIP 7: don't forget to increase your free space map settings
