stop a long running select

Hi,
Is there a way to stop a long running select statement without losing the 
connection, cursor from python?
--

-- 
John Fabiani

Re: stop a long running select

On Fri, May 1, 2009 at 9:29 PM, johnf <jfabiani@...> wrote:
> Hi,
> Is there a way to stop a long running select statement without losing the
> connection, cursor from python?

There is a connection variable called statement_timeout, which you can
use to set the maximum length of time any particular statement issued
can take in milliseconds.

So if you issue the command "SET statement_timeout TO 1000", and then
a subsequent execute() call takes longer than 1 second, you'll get a
psycopg2.extensions.QueryCanceledError exception.  At that point you
can roll back the connection and do what ever recovery is appropriate
for your application.

The transaction will have failed, but that is unavoidable: a query
being canceled is the same as a query that fails.

James.

Installation Error on OS X

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Re: Installation Error on OS X

On Sat, May 2, 2009 at 4:57 AM, theodore test <tteststudent@...> wrote:
> Hello everyone,
>
> I recently attempted to install psycopg2-2.0.10 on my Intel OS X 10.4.11
> system.  Both the "easy_install ." and regular "python setup.py install"
> methods produced similar errors.  Any thoughts or advice?
>
> Thanks in advance,
>
> Theodore Test
>

> ===PYTHON SETUP.PY INSTALL VERSION===
>
> $python setup.py install
[snip]
> "/Library/Frameworks/Python.framework/Versions/2.5.2001/lib/python2.5/distutils/cmd.py",
> line 117, in ensure_finalized
>     self.finalize_options()
>   File "setup.py", line 219, in finalize_options
>     except (Warning, w):
> NameError: global name 'w' is not defined

Looks like a bug in psycopg2's setup.py file.  Try editing it and
removing the parentheses on line 219 (so it just reads "except
Warning, w:".

This is an error/warning code path, so it is likely that there is
something else you'll need to do to install psycopg2, but this should
make the error display.

James.

Re: Installation Error on OS X

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decrease DictRow memory usage

Use "__slots__ = ('_index',)" to reserve single attribute slot for _index.
Otherwise a per-row dict is created to store object attributes...

The only danger of doing it is that if somebody uses plain DictRow and
adds new attrubutes into it, it will get error:

  row.foo = x

I'm really dubious if anybody does this.  NB, this does not apply if
somebody has subclassed DictRow, then the parent class' __slots__
is ignored.

Attached patch does the same for RealDictRow too, although I personally
do not use it.  But it seems good idea to do it there too.

On older python versions that do not support __slots__ it should be
taken as random class attribute, so should be no problem.

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Re: decrease DictRow memory usage

Il giorno lun, 04/05/2009 alle 16.22 +0300, Marko Kreen ha scritto:
> Use "__slots__ = ('_index',)" to reserve single attribute slot for
> _index.
> Otherwise a per-row dict is created to store object attributes...
> 
> The only danger of doing it is that if somebody uses plain DictRow and
> adds new attrubutes into it, it will get error:
> 
>   row.foo = x
> 
> I'm really dubious if anybody does this.  NB, this does not apply if
> somebody has subclassed DictRow, then the parent class' __slots__
> is ignored.

I agree. I someone uses custom attributes on the DictRow let me know or
I'll apply the patch. ;)

federico

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Re: decrease DictRow memory usage

Federico Di Gregorio escribió:
> Il giorno lun, 04/05/2009 alle 16.22 +0300, Marko Kreen ha scritto:
>> Use "__slots__ = ('_index',)" to reserve single attribute slot for
>> _index.
>> Otherwise a per-row dict is created to store object attributes...
>>
>> The only danger of doing it is that if somebody uses plain DictRow and
>> adds new attrubutes into it, it will get error:
>>
>>   row.foo = x
>>
>> I'm really dubious if anybody does this.  NB, this does not apply if
>> somebody has subclassed DictRow, then the parent class' __slots__
>> is ignored.
> 
> I agree. I someone uses custom attributes on the DictRow let me know or
> I'll apply the patch. ;)
> 

Hi,

I use a custom DictRow class derived from extras.DictRow. I will do this afternoon some tests to 
overload '__slots__'.

I will put here the results tomorrow.

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Re: decrease DictRow memory usage

2009/5/5 Oswaldo Hernández <listas@...>:
> Federico Di Gregorio escribió:
>>
>> Il giorno lun, 04/05/2009 alle 16.22 +0300, Marko Kreen ha scritto:
>>>
>>> Use "__slots__ = ('_index',)" to reserve single attribute slot for
>>> _index.
>>> Otherwise a per-row dict is created to store object attributes...
>>>
>>> The only danger of doing it is that if somebody uses plain DictRow and
>>> adds new attrubutes into it, it will get error:
>>>
>>>  row.foo = x
>>>
>>> I'm really dubious if anybody does this.  NB, this does not apply if
>>> somebody has subclassed DictRow, then the parent class' __slots__
>>> is ignored.
>>
>> I agree. I someone uses custom attributes on the DictRow let me know or
>> I'll apply the patch. ;)
>>
>
> Hi,
>
> I use a custom DictRow class derived from extras.DictRow. I will do this
> afternoon some tests to overload '__slots__'.
>
> I will put here the results tomorrow.

If you're subclassing DictRow then this change shouldn't have any
effect on you.  Your subclass will have an instance dictionary though,
so you won't see the memory savings.

If you want to see the memory savings though, you'll need to define
__slots__ for your subclass.  If you aren't adding any attributes,
setting it to an empty tuple will do the trick.

James.

Re: decrease DictRow memory usage

James Henstridge escribió:
> 2009/5/5 Oswaldo Hernández <listas@...>:
>> Federico Di Gregorio escribió:
>>> Il giorno lun, 04/05/2009 alle 16.22 +0300, Marko Kreen ha scritto:
>>>> Use "__slots__ = ('_index',)" to reserve single attribute slot for
>>>> _index.
>>>> Otherwise a per-row dict is created to store object attributes...
>>>>
>>>> The only danger of doing it is that if somebody uses plain DictRow and
>>>> adds new attrubutes into it, it will get error:
>>>>
>>>>  row.foo = x
>>>>
>>>> I'm really dubious if anybody does this.  NB, this does not apply if
>>>> somebody has subclassed DictRow, then the parent class' __slots__
>>>> is ignored.
>>> I agree. I someone uses custom attributes on the DictRow let me know or
>>> I'll apply the patch. ;)
>>>
>> Hi,
>>
>> I use a custom DictRow class derived from extras.DictRow. I will do this
>> afternoon some tests to overload '__slots__'.
>>
>> I will put here the results tomorrow.
> 
> If you're subclassing DictRow then this change shouldn't have any
> effect on you.  Your subclass will have an instance dictionary though,
> so you won't see the memory savings.
> 
> If you want to see the memory savings though, you'll need to define
> __slots__ for your subclass.  If you aren't adding any attributes,
> setting it to an empty tuple will do the trick.
> 

Yes i add one attribute in my custom class.

I apply the patch, then on an initial test:

. If i do nothing on my subclass, python provides a __dict__ for it. Works fine.

. Adding in the subclass:
      __slots__ = ('myattr',)
   also works fine.

Seems no problems about using slots on main DictRow and subclasing it.

Thanks,

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Oswaldo Hernández
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*****************************************
PD:
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