"RuntimeError: no codec for array element type 17189" with $1::citext[]

[rijenkii]

• asyncpg version: 0.8.4
• PostgreSQL version: 9.6.1
• Python version: 3.6.0
• Platform: Linux
• Do you use pgbouncer?: No
• Did you install asyncpg with pip?: Yes
• If you built asyncpg locally, which version of Cython did you use?:
• Can the issue be reproduced under both asyncio and
  uvloop?: Yes

Steps to reproduce:

1. CREATE DATABASE test;
2. Inside the DB: CREATE EXTENSION citext;
3. Run this python script:

import asyncio
import asyncpg

async def main():
    conn = await asyncpg.connect(database='test')
    print(await conn.fetch('SELECT $1::citext[]', ('a', 'b')))
    await conn.close()

asyncio.get_event_loop().run_until_complete(main())

4. Get an exception:

Traceback (most recent call last):
  File "test.py", line 9, in <module>
    asyncio.get_event_loop().run_until_complete(main())
  File "/usr/lib/python3.6/asyncio/base_events.py", line 466, in run_until_complete
    return future.result()
  File "test.py", line 6, in main
    print(await conn.fetch('SELECT $1::citext[]', ('a', 'b')))
  File "/usr/lib/python3.6/site-packages/asyncpg/connection.py", line 268, in fetch
    stmt = await self._get_statement(query, timeout)
  File "/usr/lib/python3.6/site-packages/asyncpg/connection.py", line 220, in _get_statement
    protocol.get_settings().register_data_types(types)
  File "asyncpg/protocol/settings.pyx", line 32, in asyncpg.protocol.protocol.ConnectionSettings.register_data_types (asyncpg/protocol/protocol.c:4669)
  File "asyncpg/protocol/settings.pyx", line 33, in asyncpg.protocol.protocol.ConnectionSettings.register_data_types (asyncpg/protocol/protocol.c:4592)
  File "asyncpg/protocol/codecs/base.pyx", line 373, in asyncpg.protocol.protocol.DataCodecConfig.add_types (asyncpg/protocol/protocol.c:16328)
RuntimeError: no codec for array element type 17189

Am I doing something wrong?

[elprans]

Appears to be a bug. citext is an extension type, so asyncpg doesn't know how to decode it in binary mode. Text mode fallback seems to be broken with arrays. I'll work on a fix shortly, meanwhile you can work around this by aliasing citext to the text codec:

await conn.set_builtin_type_codec('citext', codec_name=25)