[storm] suspected bug in storm array implementation

[Andreas Kopecky]

Hi,

I think i found a little bug in the implementation for array data
type in the postgres module of storm. Obviously postgres needs an
explicit type cast there when one tries to insert a list of null
values in a typed array column

example:

given a table like:

  create table bogus(
      realvalues real[]
  );

defining a storm class for it:

  >>> class Bogus(Storm):
  ...     realvalues List(type=Float())

bogus = Bogus()

if you now set the realvalues property to a list of None values

  >>> bogus.realvalues = [None, None]

storm tries to execute an sql statement akin to

  update set realvalues = array[Null, Null];

which results in an operational error since postgres can not
autodetect the type of null values and defaults each untyped
array to Text[]

A fix for this would be to (instead of the update statement above)
us:

  update set realvalues = cast(array[Null, Null] as real[]);

Sadly i havent found a good way to do type casts using storm syntax
so the only fix i can offer would be to do it 'manually' and add a
translation table for StormVariable types to SQL datatyped that can be
used to produce type casts in the 'compile_list_variable' function.

If wished i can provide such.

- regards, andreas kopecky

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