PostgreSQLInterface

Introduction

This package allows loading and extracting data from a PostgresSQL Database using pandas dataframes and simple SQL style methods. At the moment, only has been implemented for Heroku and GCP databases. Nonetheless, Heroku testing has been deprecated due

Extension to other vendors is easily achievable.

Structure

The library has a parent abstract class that contains the main methods, then a children class implements the particularities of a vendor, finally, a factory method handles the creation of the objects.
Below, you can find a little introduction to all relevant methods. For more information, read the doc of the method or take a look to the pytest tests in the repo.

GCP

Instantiate the class

To instantiate the class to connect to a Heroku Database:

from postgresql_interface.postgresql_interface import postgres_sql_connector_factory
db_conn = postgres_sql_connector_factory(
            vendor='gcp', host=host, database_name=database_name, 
            user_name=user_name, user_password=user_password, port=port
)

Read data from Database

To retrieve a query from the database:

my_table = db_conn.query("SELECT * FROM test.data")

It is also possible to do more complicated queries:

my_table = db_conn.query("SELECT * FROM test.data d JOIN test.references r ON d.referencesid = r.id")

Insert data

To insert data into a table:

db_conn.insert_table('test.simple', to_insert.copy())

Update a table

To update data into a table:

db_conn.update_table('test.simple', to_update, ['id', 'date'])

Delete from table

To delete from a table:

db_conn.delete_from_table('test.simple', to_delete)

Execute a general statement

To execute a general SQL statement you can use the method execute. This method returns no data. It is important to notice that it is not the SQL execute command. As an example, you can use it to create a schema:

db_conn.execute("CREATE SCHEMA test")

You can also use it to execute a stored procedure

db_conn.execute("EXECUTE test.sp_test1 @input = '%s" @ input)

Heroku

Instantiate the class

To instantiate the class to connect to a Heroku Database:

from postgresql_interface.postgresql_interface import postgres_sql_connector_factory
db_conn = postgres_sql_connector_factory(vendor='heroku', database_url=database_url)

database_url can be found on the section Config Vars inside the tab Settings of your Heroku app or on the section Database Credentials of the tab Settings of your Heroku Datastore.

Read data from Database

To retrieve a query from the database:

my_table = db_conn.query("SELECT * FROM test.data")

It is also possible to do more complicated queries:

my_table = db_conn.query("SELECT * FROM test.data d JOIN test.references r ON d.referencesid = r.id")

Insert data

To insert data into a table:

db_conn.insert_table('test.simple', to_insert.copy())

Update a table

To update data into a table:

db_conn.update_table('test.simple', to_update, ['id', 'date'])

Delete from table

To delete from a table:

db_conn.delete_from_table('test.simple', to_delete)

Execute a general statement

To execute a general SQL statement you can use the method execute. This method returns no data. It is important to notice that it is not the SQL execute command. As an example, you can use it to create a schema:

db_conn.execute("CREATE SCHEMA test")

You can also use it to execute a stored procedure

db_conn.execute("EXECUTE test.sp_test1 @input = '%s" @ input)

Tests

To be able to execute the tests, it is necessary to provide a '.env' file with the url to connect to a GCP database. Currently, Heroku testing is disabled due to change in pricing.