Sample synchronous Lambda function¶

This topic includes code for a sample Lambda Function that you can use as-is to create your first external function, or that you can use as a starting point for a custom Lambda Function.

This function is synchronous.

(A separate asynchronous example is also available.)

This example is written in Python.

This sample synchronous Lambda Function extracts each row, processes it, and returns a value for that row. Each output value is simply an array that contains a copy of each of the values in the input row. The returned array is treated as a SQL VARIANT by Snowflake.

import json

def lambda_handler(event, context):

    # 200 is the HTTP status code for "ok".
    status_code = 200

    # The return value will contain an array of arrays (one inner array per input row).
    array_of_rows_to_return = [ ]

    try:
        # From the input parameter named "event", get the body, which contains
        # the input rows.
        event_body = event["body"]

        # Convert the input from a JSON string into a JSON object.
        payload = json.loads(event_body)
        # This is basically an array of arrays. The inner array contains the
        # row number, and a value for each parameter passed to the function.
        rows = payload["data"]

        # For each input row in the JSON object...
        for row in rows:
            # Read the input row number (the output row number will be the same).
            row_number = row[0]

            # Read the first input parameter's value. For example, this can be a
            # numeric value or a string, or it can be a compound value such as
            # a JSON structure.
            input_value_1 = row[1]

            # Read the second input parameter's value.
            input_value_2 = row[2]

            # Compose the output based on the input. This simple example
            # merely echoes the input by collecting the values into an array that
            # will be treated as a single VARIANT value.
            output_value = ["Echoing inputs:", input_value_1, input_value_2]

            # Put the returned row number and the returned value into an array.
            row_to_return = [row_number, output_value]

            # ... and add that array to the main array.
            array_of_rows_to_return.append(row_to_return)

        json_compatible_string_to_return = json.dumps({"data" : array_of_rows_to_return})

    except Exception as err:
        # 400 implies some type of error.
        status_code = 400
        # Tell caller what this function could not handle.
        json_compatible_string_to_return = event_body

    # Return the return value and HTTP status code.
    return {
        'statusCode': status_code,
        'body': json_compatible_string_to_return
    }

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