Client Python (provisa-client)

Client Python per Provisa. Fornisce quattro interfacce:

Interfaccia	Caso d'uso
ProvisaClient	Query GraphQL, Arrow Flight, output DataFrame
DB-API 2.0 (connect)	Interfaccia database Python standard (PEP 249) (REQ-268)
Dialetto SQLAlchemy	Strumenti BI, ORM, read_sql di Pandas (REQ-270)
ADBC	Streaming columnar Arrow-native via Flight (REQ-271)

Installazione

pip install provisa-client                      # core (ProvisaClient + DB-API)
pip install "provisa-client[pandas]"            # adds pandas
pip install "provisa-client[sqlalchemy]"        # adds SQLAlchemy dialect
pip install "provisa-client[adbc]"              # adds ADBC over Arrow Flight

---

ProvisaClient

Avvio rapido

from provisa_client import ProvisaClient

client = ProvisaClient(
    "http://localhost:8001",
    username="alice",
    password="secret",
)

Query GraphQL

# Raw response dict
result = client.query("{ orders { id amount region } }")

# With variables
result = client.query(
    "query Q($region: String!) { orders(region: $region) { id amount } }",
    variables={"region": "west"},
)

# pandas DataFrame (first root field is flattened)
df = client.query_df("{ orders { id amount region } }")

Async

result = await client.aquery("{ orders { id amount } }")

Arrow Flight (columnar ad alto throughput)

Usa Flight per grandi result set — i dati vengono trasmessi in streaming come Arrow record batch senza essere materializzati sul server. (REQ-143, REQ-145)

import pyarrow as pa

table: pa.Table = client.flight("{ orders { id amount region } }")
df = client.flight_df("{ orders { id amount region } }")

Flight si connette alla porta 8815 per default. (REQ-143) Sovrascrivi con flight_port=:

client = ProvisaClient("http://prod.example.com", flight_port=8815)

Esplorazione del catalogo

tables_df = client.list_tables()

Riferimento connessione

Parametro	Default	Descrizione
url	http://localhost:8001	URL base del server Provisa
token	None	Bearer token; omesso per l'autenticazione con password (REQ-606)
role	"admin"	Ruolo inviato con ogni richiesta (REQ-273)
flight_port	8815	Porta gRPC di Arrow Flight (REQ-143)

Gestione errori

query() solleva httpx.HTTPStatusError in caso di errori HTTP. (REQ-607) query_df() solleva RuntimeError se la risposta contiene errori GraphQL. (REQ-607)

---

DB-API 2.0

Interfaccia standard PEP 249. (REQ-268) Funziona con qualsiasi strumento che accetta una connessione DB-API.

from provisa_client import connect

conn = connect(
    "http://localhost:8001",
    username="alice",
    password="secret",
    role="admin",       # optional, default "admin"
)

Esecuzione di query

Il cursore accetta GraphQL o SQL — rilevato automaticamente. (REQ-268, REQ-274)

cur = conn.cursor()

# GraphQL
cur.execute("{ orders { id amount region } }")
rows = cur.fetchall()           # list of tuples
one  = cur.fetchone()           # single tuple or None
many = cur.fetchmany(size=50)   # up to N tuples

# SQL (routed through Stage 2 governance)
cur.execute("SELECT id, amount FROM orders WHERE region = 'west'")
rows = cur.fetchall()

Metadati colonna

cur.execute("{ orders { id amount } }")
print(cur.description)
# [('id', None, ...), ('amount', None, ...)]
print(cur.rowcount)

Parametri nominati

cur.execute(
    "SELECT * FROM orders WHERE region = :region",
    {"region": "west"},
)

Context manager

with connect("http://localhost:8001", username="alice", password="secret") as conn:
    with conn.cursor() as cur:
        cur.execute("{ orders { id amount } }")
        print(cur.fetchall())

---

Dialetto SQLAlchemy

pip install "provisa-client[sqlalchemy]"

Schema URL: provisa+http:// o provisa+https:// (REQ-270)

from sqlalchemy import create_engine, text

engine = create_engine("provisa+http://alice:secret@localhost:8001")

with engine.connect() as conn:
    result = conn.execute(text("{ orders { id amount region } }"))
    for row in result:
        print(row)

Con pandas

import pandas as pd

df = pd.read_sql("{ orders { id amount } }", engine)

Parametri URL

Parametro	Descrizione	Default
role	Ruolo Provisa	admin

engine = create_engine(
    "provisa+http://alice:secret@localhost:8001?role=analyst"
)

Introspezione dello schema

Il dialetto implementa get_table_names(), get_columns(), e has_table() — gli strumenti di catalogo (DBeaver, SQLAlchemy automap) possono ispezionare lo schema. (REQ-363, REQ-270)

---

ADBC

Arrow Database Connectivity basata su Arrow Flight. (REQ-271) Restituisce direttamente pyarrow.Table — nessuna deserializzazione JSON. (REQ-271)

pip install "provisa-client[adbc]"

from provisa_client.adbc import adbc_connect

conn = adbc_connect(
    "http://localhost:8001",
    user="alice",
    password="secret",
    role="analyst",   # optional; server validates the requested role
    port=8815,        # Arrow Flight port (REQ-711)
)

Recupero come Arrow Table

with conn.cursor() as cur:
    cur.execute("{ orders { id amount region } }")
    table = cur.fetch_arrow_table()   # pyarrow.Table
    df = table.to_pandas()

Recupero come tuple

with conn.cursor() as cur:
    cur.execute("{ orders { id amount } }")
    rows = cur.fetchall()    # list of tuples
    one  = cur.fetchone()    # single tuple or None

Metadati colonna

cur.execute("{ orders { id amount } }")
print(cur.description)
# [('id', None, ...), ('amount', None, ...)]

Context manager

with adbc_connect("http://localhost:8001", user="alice", password="secret") as conn:
    with conn.cursor() as cur:
        cur.execute("{ orders { id amount } }")
        table = cur.fetch_arrow_table()

ADBC si connette al server Flight sulla porta 8815 per default. (REQ-143) Passa port= per raggiungere un server Flight collegato a una porta non predefinita. (REQ-711)