docs/source/python/recipe/postgresql_get_query_schema.py

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# RECIPE STARTS HERE

#: ADBC lets you get the schema of a result set, without executing the query.

import os

import pyarrow

import adbc_driver_postgresql.dbapi

uri = os.environ["ADBC_POSTGRESQL_TEST_URI"]
conn = adbc_driver_postgresql.dbapi.connect(uri)

#: We'll create an example table to test.
with conn.cursor() as cur:
    cur.execute("DROP TABLE IF EXISTS example")
    cur.execute("CREATE TABLE example (ints INT, bigints BIGINT)")

conn.commit()

expected = pyarrow.schema(
    [
        ("ints", "int32"),
        ("bigints", "int64"),
    ]
)

with conn.cursor() as cur:
    assert cur.adbc_execute_schema("SELECT * FROM example") == expected

    #: PostgreSQL doesn't know the type here, so it just returns a guess.
    assert cur.adbc_execute_schema("SELECT $1 AS res") == pyarrow.schema(
        [
            ("res", "string"),
        ]
    )

conn.close()