python udf in redshift - support for nested udf

Question

I am trying to implement a nested udf in redshift.

select 
     custom_function(custom_function('', column1), column2) 
from 
     table1

But it says nested udfs are not supported. can someone help me here?

Tried using the python library approach mentioned in the answer and its shown below!!

class f_string:
   def __init__(self, current_value, key, value):
   self.current_value = current_value
   self.key = key
   self.value = value

def f_make_json(self):
   import json
   current_value = json.loads(self.current_value)
   self.value.replace('"', '\"')
   current_value[self.key] = self.value
   return (json.dumps(current_value))

AlexYes · Accepted Answer · 2018-10-02 08:46:39Z

0

you have to organize the UDF that you'd like to nest as a Python library and import that library to your cluster, here is the instruction

answered Oct 2, 2018 at 8:46

AlexYes

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6 Comments

AlexYes Over a year ago

not sure I understand how they are supposed to be nested and what exactly did you do in terms of library bundling

user2728024 Over a year ago

i am trying to create a json string. something like this make_json(make_json('{}', 'key1', 'value1'), 'key2', 'value2') which will return {'key1':'value1', 'key2':'value2'}

AlexYes Over a year ago

ah, it's the same function nested... I thought it's different functions nested. Can you try the first function in a subquery and the second function in the outer query?

user2728024 Over a year ago

there could be more than 2 variables. so having multiple subqueries wont be the ideal solution here!!

AlexYes Over a year ago

after all, why don't you just build your json using concatenation operator? I was always doing this and it was pretty easy and clean with proper formatting of the code like every key/value pair on a new line and proper indentation for embedded objects

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