flightsql-dbapi 0.2.1

DB API 2 and SQLAlchemy adapter for Flight SQL

:warning: This library is experimental and under active development. The APIs it provides could change at any time so use at your own risk.

Overview

This library provides a DB API 2 interface and SQLAlchemy Dialect for Flight SQL.

Initially, this library aims to ease the process of connecting to Flight SQL APIs in Apache Superset.

The primary SQLAlchemy Dialect provided by flightsql-dbapi targets the DataFusion SQL execution engine. However, there extension points to create custom dialects using Flight SQL as a transport layer and for metadata discovery.

Installation

$ pip install flightsql-dbapi

Usage

DB API 2 Interface (PEP-249)

from flightsql import connect, FlightSQLClient

client = FlightSQLClient(host='upstream.server.dev')
conn = connect(client)
cursor = conn.cursor()
cursor.execute('select * from runs limit 10')
print("columns:", cursor.description)
print("rows:", [r for r in cursor])

SQLAlchemy

import flightsql.sqlalchemy
from sqlalchemy import func, select
from sqlalchemy.engine import create_engine
from sqlalchemy.schema import MetaData, Table

engine = create_engine("datafusion+flightsql://john:[e-mail]:443")
runs = Table("runs", MetaData(bind=engine), autoload=True)
count = select([func.count("*")], from_obj=runs).scalar()
print("runs count:" count)
print("columns:", [(r.name, r.type) for r in runs.columns])

# Reflection
metadata = MetaData(schema="iox")
metadata.reflect(bind=engine)
print("tables:", [table for table in metadata.sorted_tables])

Custom Dialects

If your database of choice can't make use of the Dialects provided by this library directly, you can extend flightsql.sqlalchemy.FlightSQLDialect as a starting point for your own custom Dialect.

from flightsql.sqlalchemy import FlightSQLDialect
from sqlalchemy.dialects import registry

class CustomDialect(FlightSQLDialect):
    name = "custom"
    paramstyle = 'named'

    # For more information about what's available to override, visit:
    # https://docs.sqlalchemy.org/en/14/core/internals.html#sqlalchemy.engine.default.DefaultDialect

registry.register("custom.flightsql", "path.to.your.module", "CustomDialect")

DB API 2 Connection creation is provided by FlightSQLDialect.

The core reflection APIs of get_columns, get_table_names and get_schema_names are implemented in terms of Flight SQL API calls so you shouldn't have to override those unless you have very specific needs.

Directly with flightsql.FlightSQLClient

from flightsql import FlightSQLClient


client = FlightSQLClient(host='upstream.server.dev',
                         port=443,
                         token='rosebud-motel-bearer-token')
info = client.execute("select * from runs limit 10")
reader = client.do_get(info.endpoints[0].ticket)

data_frame = reader.read_all().to_pandas()

Authentication

Both Basic and Bearer Authentication are supported.

To authenticate using Basic Authentication, supply a DSN as follows:

datafusion+flightsql://user:password@host:443

A handshake will be performed with the upstream server to obtain a Bearer token. That token will be used for the remainder of the engine's lifetype.

To authenticate using Bearer Authentication directly, supply a token query parameter instead:

datafusion+flightsql://host:443?token=TOKEN

The token will be placed in an appropriate Authentication: Bearer ... HTTP header.

Additional Query Parameters

Name	Description	Default
insecure	Connect without SSL/TLS (h2c)	false
disable_server_verification	Disable certificate verification of the upstream server	false
token	Bearer token to use instead of Basic Auth	empty

Any query parameters not specified in the above table will be sent to the upstream server as gRPC metadata.