c/driver/postgresql: GetTableSchema does not properly handle catalog or db_schema parameters

[joellubi]

When calling GetTableSchema on the postgresql driver, the following behavior is observed:

1. catalog is ignored
2. The query produced when db_schema is set causes a postgres syntax error

I have been able to reproduce the issues with Go and Python bindings. Below are the steps for reproducing in Python:

from adbc_driver_postgresql import dbapi

uri = "postgresql://postgres@localhost:5432/postgres"

# Setup example
with dbapi.connect(uri) as conn:
    with conn.cursor() as cur:
        cur.execute("CREATE TABLE foo (bar int)")
    conn.commit()

# Correct, inferring catalog: postgres, db_schema: public
with dbapi.connect(uri) as conn:
    schema = conn.adbc_get_table_schema("foo")
print(schema) # bar: int32

#  Incorrect, catalog_filter is ignored
with dbapi.connect(uri) as conn:
    schema = conn.adbc_get_table_schema("foo", catalog_filter="doesnt_exist")
print(schema) # bar: int32

#  Incorrect, raises exception when foo should be found in public schema
with dbapi.connect(uri) as conn:
    schema = conn.adbc_get_table_schema("foo", db_schema_filter="public")

# Exception raised
OperationalError: ADBC_STATUS_IO (10): [libpq] Failed to prepare query: ERROR:  syntax error at or near "$2"
LINE 1: ...= typ.oid WHERE attr.attnum >= 0 AND cls.oid = $1.$2::regcla...
                                                             ^

Query was:SELECT attname, atttypid FROM pg_cat

Version Info
Python: 3.11.4
adbc_driver_postgresql: 0.8.0

[joellubi]

Relevant part of the C++ code for reference: https://github.com/apache/arrow-adbc/blob/main/c/driver/postgresql/connection.cc#L1144

[lidavidm]

In Postgres, you can only access the database (catalog) you're connected to.

A client connection to the server can only access data in a single database, the one specified in the connection request.

(https://www.postgresql.org/docs/current/ddl-schemas.html)

However we should support schemas properly.