UDCF Scalar Example - Teradata VantageCloud Lake

AWS Lambda Function

# hash_256.py
# A simple lambda function to concatenate scalar UDCF input
# Returns a sha256 hexdigest hash of the concatenated arguments

from hashlib import sha256

# map the column to a string type
def transform(args):
    nargs = len(args)

    # concatenate all the arguments together
    result = ''.join(map(str, args))

    # hash the result into a hexdigest string prefix
    hash = sha256(result.encode())
    return hash.hexdigest()[:7]

# concatenate arguments of the scalar udcf into a single string
def lambda_handler(event, context):
    # the data key is part of the default JSON format in the event dictionary
    assert "data" in event

    # scalar udcfs only pass a single row to the lambda function
    rows = event['data']
    assert len(rows) == 1

    # the row contains arguments passed to the scalar udcf in the SQL query
    row = rows[0]
    assert len(row) > 1

    # the first element of the row is a virtual index value
    index = row[0]

    # the return value of the lambda function that follows the default JSON format
    output = {"data": []}

    # the index is needed as the first element in the output row
    # to follow the default JSON format
    output_row = [index]

    # process the arguments
    result = transform(row[1:])

    # add the final result to the output row
    output_row.append(result)   
    output["data"].append(output_row)
    return output

Output

See the output for testing the lambda_handler:

 event = {
   "data": [ [0, ‘test’] ]
 }

{'data': [[0, '9f86d08']]}

UDCF Execution

 BTEQ -- Enter your SQL request or BTEQ command: 

INSERT INTO demo_table VALUES (
  1, 
  'test'
);

 *** Insert completed. One row added.
 *** Total elapsed time was 1 second.

INSERT INTO demo_table VALUES (
  2, 
  'hello'
);

 *** Insert completed. One row added.
 *** Total elapsed time was 1 second.

INSERT INTO demo_table VALUES (
  3, 
  'world'
);

 *** Insert completed. One row added. 
 *** Total elapsed time was 1 second.

 BTEQ -- Enter your SQL request or BTEQ command: 
select sha_256(col2) from demo_table;

 *** Query completed. 3 rows found. One column returned. 
 *** Total elapsed time was 1 second.

sha_256(col2)
----------
9f86d08
2cf24db
486ea46