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Introductie tot Data Engineering

Vincent Vankrunkelsven

Data Engineer @ DataCamp

De ETL-functie

def extract_table_to_df(tablename, db_engine):
  return pd.read_sql("SELECT * FROM {}".format(tablename), db_engine)

def split_columns_transform(df, column, pat, suffixes): # Converts column into str and splits it on pat...
def load_df_into_dwh(film_df, tablename, schema, db_engine): return pd.to_sql(tablename, db_engine, schema=schema, if_exists="replace")
db_engines = { ... } # Needs to be configured def etl(): # Extract film_df = extract_table_to_df("film", db_engines["store"]) # Transform film_df = split_columns_transform(film_df, "rental_rate", ".", ["_dollar", "_cents"]) # Load load_df_into_dwh(film_df, "film", "store", db_engines["dwh"])
Introductie tot Data Engineering

Airflow-opfrisser

Airflow-logo

 

  • Workflowplanner
  • Python
  • DAG's

Conceptueel voorbeeld van een DAG

  • Taken gedefinieerd in operators (bijv. BashOperator)
Introductie tot Data Engineering

Plannen met DAG's in Airflow

from airflow.models import DAG

dag = DAG(dag_id="sample",
          ...,
          schedule_interval="0 0 * * *")

# cron
# .------------------------- minuut           (0 - 59)
# | .----------------------- uur              (0 - 23)
# | | .--------------------- dag v/d maand    (1 - 31)
# | | | .------------------- maand            (1 - 12)
# | | | | .----------------- dag v/d week     (0 - 6)
# * * * * * <command>

# Voorbeeld
0 * * * * # Elk uur op minuut 0

cf. https://crontab.guru

Introductie tot Data Engineering

Het DAG-definitiebestand

from airflow.models import DAG
from airflow.operators.python_operator import PythonOperator

dag = DAG(dag_id="etl_pipeline",
          schedule_interval="0 0 * * *")

etl_task = PythonOperator(task_id="etl_task", python_callable=etl, dag=dag)
etl_task.set_upstream(wait_for_this_task)
Introductie tot Data Engineering

Het DAG-definitiebestand

from airflow.models import DAG
from airflow.operators.python_operator import PythonOperator

...

etl_task.set_upstream(wait_for_this_task)

Opgeslagen als etl_dag.py in ~/airflow/dags/

Introductie tot Data Engineering

Airflow-UI

Screenshot van Airflow-UI

Introductie tot Data Engineering

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Introductie tot Data Engineering

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