#106 begin() lost

[Den Ivanov]

'Connection' object has no attribute 'begin'

[Andy Dustman]

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It's not lost; I took it out. It was a non-standard
extension, and seems slightly deprecated in favor of using
START TRANSACTION, which is more standard SQL.

http://dev.mysql.com/doc/mysql/en/COMMIT.html

Additionally, there are now (in MySQL-4.1) C API calls for
commit, rollback, and autocommit, but nothing for begin or
start transaction.

You could work around this two ways:

1) Subclass Connection and add the begin() method back it
(it only ever did self.query("BEGIN");)

2) Change your app to do c.execute("BEGIN")

I'll leave this unresolved for awhile; it wouldn't be a big
deal to put it back in, but using it in your would adversely
affect it's portability. I'll also have to see if other
database modules implement this (like psycopg), in which
case, it's less of a problem. I'm leaving begin() in the
1.0.x series.

[Den Ivanov]

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Ok, then remove begin() from documentation.

[Kyle VanderBeek]

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No offense, but this is super lame. It broke a ton of
code for me. I'd like to see it re-added and go through
proper deprecation. An interface change like this should go
through a rev with a deprecation notice, even if it was
indeed a nonstandard piece of functionality.

I'm working around it, but this seems totally hostile.

[Andy Dustman]

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Here's the super lame workaround:

def begin():
print "fix your code"

db.begin = begin

Auto-commit is on by default, so you don't need begin unless
you change this for some reason.

Less lame work-around:

import MySQLdb
import MySQLdb.connections

class MyConnection(MySQLdb.connections.Connection):

def begin(self):
    from warnings import warn
    warn("fix your code", DeprecationWarning)
    self.query("BEGIN")

MySQLdb.connect = MyConnection

[Kyle VanderBeek]

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I didn't mean to raise your ire. I'm just giving advice
while showing my frustration. Had the whole 1.1.x series
had a docstring in it that said "This is a nonstandard call.
It is deprecated and will be removed in future versions of
this library." then I wouldn't have minded. Then it is my
fault for ignoring a deprecation warning.

Instead, I find out that I need a recent bugfix, but now
have to touch up thousands of lines of code to either
instantiate my wrapper class, run a patched version of the
module, or convert code to execute begin.

I'm not saying it was bad thing to remove it. I'm just
advocating graceful deprecation. The sudden interface
change is likely to anger/frustrate downstream developers
who use MySQLdb and have transaction-sensative applications.

I'd like to see it re-added like this, and left for a few
versions, thereby warning the entire devloper community of
the code-breaking change to come:

def begin():
"""Start a transaction. This is a non-standard
extension and will be removed in a future version. Use
cursor.execute("BEGIN") instead."""
self.query("BEGIN")

[Jeffrey Wescott]

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Yes, this is pretty weak. It should have been deprecated instead, and
removed later.

[Andy Dustman]

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This is fixed in CVS in branch-1-2. It won't be going into
the trunk because that's where 1.3 will be developed. Follow
the CVS checkout instructions but add -r branch-1-2 to the
parameters.

Test this and get back to me. I'll release a beta within the
next week.

[Kyle VanderBeek]

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Excellent! My only nit to pick would be that adding the
"stacklevel=2" extra argument to warn() would be really
cool. That makes it print the warning, and the line number
of the calling function instead of this function. It
basically says "here is where you called the deprecated
function from". Very handy.

[Andy Dustman]

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OK, I'll do this too.

[Kyle VanderBeek]

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The current branch-1-2 works well enough for me. The
stacklevel argument would be neat, but 1.2.1 getting dropped
would be even cooler.