docs/source/python/recipe/postgresql_get_table_schema.py

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# RECIPE STARTS HERE

#: ADBC lets you get the schema of a table as an Arrow schema.

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 some example tables to test.
with conn.cursor() as cur:
    cur.execute("DROP TABLE IF EXISTS example")
    cur.execute("CREATE TABLE example (ints INT, bigints BIGINT)")

    cur.execute("CREATE SCHEMA IF NOT EXISTS other_schema")
    cur.execute("DROP TABLE IF EXISTS other_schema.example")
    cur.execute("CREATE TABLE other_schema.example (strings TEXT, values NUMERIC)")

conn.commit()

#: By default the "active" catalog/schema are assumed.
assert conn.adbc_get_table_schema("example") == pyarrow.schema(
    [
        ("ints", "int32"),
        ("bigints", "int64"),
    ]
)

#: We can explicitly specify the PostgreSQL schema to get the Arrow schema of
#: a table in a different namespace.
#:
#: .. note:: In PostgreSQL, you can only query the database (catalog) that you
#:           are connected to.  So we cannot specify the catalog here (or
#:           rather, there is no point in doing so).
#:
#: Note that the NUMERIC column is read as a string, because PostgreSQL
#: decimals do not map onto Arrow decimals.
assert conn.adbc_get_table_schema(
    "example",
    db_schema_filter="other_schema",
) == pyarrow.schema(
    [
        ("strings", "string"),
        ("values", "string"),
    ]
)

conn.close()