Parse a unix timestamp with proper handling for milliseconds

parse_unixtime.py

from __future__ import unicode_literals

import pytest

from starscream.pipeline.stage import TransformStage

from pyspark.sql import functions as F, types as T

from starscream.contract import Contract
from starscream.utils.dataframe import as_dicts, from_dicts

import pyspark.sql.types as T

contract = Contract({
    'id': {'type': T.LongType()},
    'updated_at': {'type': T.LongType()},
})


input_df = from_dicts(sc, contract, [
    {'id': 1, 'updated_at': 1596503049026},
    {'id': 2, 'updated_at': 1596503049773},
    {'id': 3, 'updated_at': 1596503049066},
    {'id': 4, 'updated_at': 1596503049999},
])

input_df.select(['id', 'updated_at']).show()


class MyStage(TransformStage):
    """
    Proper handling of unix timestamp with milliseconds:

    1) Take input unix timestamp with milliseconds 1596503049026
    2) Get the unix timestamp in seconds, '1596503049', and the milliseconds component '026'
    3) Convert the unix timestamp in seconds to a normal timestamp, i.e. '1596503049' --> '2020-08-04 01:04:09'
    4) Add in the milliseconds component via string concatenation, '2020-08-04 01:04:09' + '.' + '026'
    5) Convert that string back to a timestamp, '2020-08-04 01:04:09.026'

    """
    OUTPUT = Contract({
        'id': {'type': T.LongType()},
        'updated_at': {'type': T.LongType()}, # original unix ts: 1596503049026
        'updated_at_ts_ms': {'type': T.TimestampType()}, # Timestamp with milliseconds, i.e. 2020-08-04 01:04:09.026
    })
    
    def apply(self, sc, my_input_df):
        # TODO: add an assert that updated_at must be a 13 digit long
        return (
            my_input_df
            .withColumn('updated_at_unix_ms_str', F.col('updated_at').cast(T.StringType()))
            .withColumn('updated_at_unix_s', F.substring(F.col('updated_at_unix_ms_str'), 1, 10).cast(T.LongType()))
            .withColumn('updated_at_ms_str', F.substring(F.col('updated_at_unix_ms_str'), -3, 3))
            .withColumn('updated_at_ts_s_str', F.from_unixtime('updated_at_unix_s'))
            .withColumn('updated_at_ts_ms_str', F.concat(F.col('updated_at_ts_s_str'), F.lit('.'), F.col('updated_at_ms_str')))
            .withColumn('updated_at_ts_ms', F.to_timestamp(F.col('updated_at_ts_ms_str')))
            .select(self.OUTPUT.keys())
        )

output_df = MyStage().apply(sc, input_df)
output_df.show()
output_df.toPandas()

Well I way over-engineered this.... apparently you can just do:

(F.col('updated_at') / 1000).astype('timestamp') and spark will automagically parse as a proper timestamp with milliseconds precision. Same caveat as above that your timestamp column ('updated_at'), must be 13 digits.