define_table number of arguments limited to 255

[Richard]

Hello,

I kind of it an limit... I was refactoring some model definition and merging multiple tables into one and I had this error :

Traceback (most recent call last):

  File "/web2py/gluon/restricted.py", line 226, in restricted

    ccode = compile2(code, layer)

  File "/web2py/gluon/restricted.py", line 209, in compile2

    return compile(code.rstrip().replace('\r\n', '\n') + '\n', layer, 'exec')

  File "applications/sgddms/models/result.py", line 4

    db.define_table('table_name',

SyntaxError: more than 255 arguments

From my limited investigation it appears to come from compile2 function : https://github.com/web2py/web2py/blob/9f69ab9753ce32dba1174b02181e7bbf9ff0987a/gluon/restricted.py#L204

And it related to second answer explanations here : https://stackoverflow.com/questions/714475/what-is-a-maximum-number-of-arguments-in-a-python-function

Where python bytecode compilation impose a limit over the number of positional arguments supported by a given object... It appears that it could be workaround using *args or **kwargs, but I guess in or case it wouldn't work to refactor pyDAL to avoid this limit as I guess we use positional arguments to determine where fields appears in form...

Can we fix that in order to support max amount of columns supported by given database engine (postgres = 1000 to my knowledge)??

Thanks

Richard

[Anthony]

It's a Python limitation -- what could we do to fix it? Can't you put your fields in a list and then do:

db.define_table('mytable', *list_of_fields)

Anthony

[Richard Vézina]

Maybe... Will try that... Do you see any drawback of using definte_table that  way??

Richard

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[Richard Vézina]

Seems to work just fine so far...

Richard

[Anthony]

On Wednesday, October 4, 2017 at 1:34:44 PM UTC-4, Richard wrote:

Maybe... Will try that... Do you see any drawback of using definte_table that  way??

No.

[Anthony]

Note, here is an example where this pattern is used in the web2py code base:

https://github.com/web2py/web2py/blob/5975e4767fd7339b5c588305ec9e8eebd9c079c5/gluon/sqlhtml.py#L1927

[Richard Vézina]

Great!

I am happy this one is a no brainer, I was afraid to have to work another solution or refactor actual model that I intended to use...

Thanks and regards Anthony

Richard

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