Psycopg psycopg

Comments and changes to this ticket

• 

  Daniele Varrazzo October 11th, 2013 @ 10:41 PM

  • State changed from “new” to “invalid”

  Caching of the attribute is necessary but it's local to the scope you have registered the composite.

  Avoid using register_composite with global=True: use it on the connection or on the cursor, and dispose the connection or the cursor after the data type is changed. Alternatively just call register_composite again.

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  Chad Whitacre October 12th, 2013 @ 02:13 AM

  Thanks @dvarrazzo. Scoping our register_composite calls to the connection or cursor would narrow the race condition, but wouldn't eliminate it. I'm not sure we can eliminate it, though, so what would you think of raising a subclass of DataError in CompositeCaster.parse instead of DataError itself? That way our application could catch that (without swallowing other, unrelated DataErrors) and then retry register_composite or take other measures. Would this be acceptable to you?

• 

  Daniele Varrazzo October 14th, 2013 @ 11:15 AM

  Hello Chad,

  the use case for such subclass is fairly restricted, and I think it would be more the hassle to document it than its general usefulness, not to mention that people is usually unhappy to get a new feature in rel. 2.5.2.

  So my suggestion is you make your own subclass of the adapter, which should be something as easy as (untested):

  class CompositeChanged(DataError):
      pass
  
  class OurCompositeCaster(CompositeCaster):
      def parse(self, s, curs):
          try:
              return super(OurCompositeCaster, self).parse(s, curs)
          except DataError, e:
              raise CompositeChanged(str(e))
  

  this should do everything you need.

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  Chad Whitacre October 14th, 2013 @ 09:04 PM

  Sounds sensible. Thanks Daniele! :-)