Rawl

An odd raw sql abstraction library. It might suck.

NOTE: This is not an ORM, nor intended to hide the database. It's more or less a wrapper around psycopg2. It will not create the database for you, either. Nor should it! Proper database design can not be abstracted away. That said, with some care you can execute a set of queries to create your schema if needed. See the tests for an example.

Usage

Simple Connection

The most rudimentary way to use Rawl is with RawlConnection. It's basically just a wrapper for psycopg2's connection.

with RawlConnection("postgresql://myUser:[email protected]/my_database") as connection:
    cursor = connection.cursor()
    cursor.execute("SELECT * from my_table;")
    results = cursor.fetchall()

This isn't really the useful part of Rawl, so perhaps you'd rather build data controllers or models.

Models

Create model classes that derrive from RawlBase. RawlBase provides some useful methods:

• query - Executes a query from provided SQL string template and parameters
• select - Executes a query from provided SQL string template, columns, and parameters
• process_columns - Converts an iterable to a list of strings that represent column names.

These are also available, though not especially inteded to be used by the user unless necessary.

• _assemble_select - Put together a compiled Psycopg2 SQL SELECT from an SQL string template and query parameters.
• _assemble_simple - Put together a compiled Psycopg2 SQL statement from an SQL string template and query parameters.
• _execute - Executes an assembled SQL query

Here's a very simple example of a model:

from rawl import RawlBase

DSN = "postgresql://myUser:[email protected]/my_db"


class StateModel(RawlBase):
    def __init__(self):
        # Init the parent
        super(StateModel, self).__init__(DSN, table_name='state', 
            columns=['state_id', 'name'])

    def get_name(self, pk):
        """ My special method returning only a name for a state """
        
        result = self.select("SELECT {0} FROM state WHERE state_id = %s;", 
            ['name'], pk)
        
        # Return first row column 'name'
        return result[0].name

if __name__ == "__main__":
    for state in StateModel().all(): 
        print(state.name)

And of course you can add your own methods for various specialty queries or anything you want.

Results

Unless otherwise altered by the implemented methods, results returned from any query are always a list of RawlResult objects. You can treat these as if they were dicts, objects, or lists. For instance:

for row in StateModel().all():
    
    # These are all the same
    print(row.state_id)
    print(row['state_id'])
    print(row[0])

    # Or iterate through the columns
    for col in row:
        print(col)

RawResult should be suitable for serialization(pickling), but should you need to convert to a python type, use RawResult.to_dict() or RawResult.to_list().

Transactions

There's some rudimentary support for transactions within models as well. You can start a transaction by calling start_transaction() on the model and finalize the transaction either by calling rollback() or commit().

model = StateModel(DSN)
model.start_transaction()
model.insert_dict({"state_id": "PA", "name": "Pennsylvania"})
model.commit()

JSON Encoding

In case you want to convert your query results directly to a JSON string for output, you can use RawlJSONEncoder.

json.dumps(StateModel().all(), cls=RawlJSONEncoder)

Testing

Install the dependencies.

pip install -r requirements.dev.txt

Run pytest with the following environmental variables.

• PG_DSN - Database connection string for a non-test database. If a single instance install, database postgres will do.
• RAWL_DSN - Connection string for the test database. It will be dropped and recreated.

The -v switch is for logging verbosity. Add more v's for a lower log level. For example:

PG_DSN="postgresql://myUser:[email protected]:5432/postgres" RAWL_DSN="postgresql://myUser:[email protected]:5432/rawl_test" pytest -s -vvvv

Release

This should take care of doing a release(including a PyPi release)

• Bump version in setup.py and commit
• Tag version(e.g. git tag v0.1.0b1)
• Push to origin