How to Compare the BigQuery table schemas between many tables from different datasets

Description (The problem)

The case: We have multiple datasets in BigQuery that receive data from various sources, such as Azure, AWS, and GCP etc... These datasets have identical table names.

The 1B$ question: How can we efficiently check the schemas of these tables in a short period of time without manual intervention?

Solution (Write the script)

To check and compare the schema of many BigQuery SQL tables using a Python script, we can utilize the BigQuery Python client library.

Here's an example of how we can achieve this using one simple script named: bq-schema-comparator

This script retrieves the schemas of many tables using the get_table_schema() function and then compares the schemas using a simple equality check.

By running this Python script, you can check and compare the schema of three BigQuery SQL tables and identify any differences or similarities.

Here's an example of how you can achieve this:

1. Install the google-cloud-bigquery library by running the following command:

pip install google-cloud-bigquery

1. Import the necessary modules in your Python script:

from google.cloud import bigquery

1. Set up the BigQuery client:

# Create a client instance
client = bigquery.Client()

1. Define a function to retrieve the schema of a table:

def get_table_schema(project_id, dataset_id, table_id):
    table_ref = client.dataset(dataset_id, project=project_id).table(table_id)
    table = client.get_table(table_ref)
    return table.schema

1. Compare the schemas of the three tables:

# Define the table names
table1_name = 'table1'
table2_name = 'table2'
table3_name = 'table3'

# Retrieve the schemas of the tables
table1_schema = get_table_schema('project_id', 'dataset_id', table1_name)
table2_schema = get_table_schema('project_id', 'dataset_id', table2_name)
tableN_schema = get_table_schema('project_id', 'dataset_id', tableN_name)

# Compare the schemas field by field
# You can write your own comparison logic here based on your requirements
if table1_schema == table2_schema and table2_schema == tableN_schema:
    print("All table schemas are identical.")
    print(table1_schema) # To see the schema in details!
else:
    print("Table schemas have differences.")

Double Check!

• Make sure to replace 'project_id' and 'dataset_id' with your actual project and dataset IDs.
• Adjust the table names (table1_name, table2_name, tableN_name) as per your table names.