decimal.InvalidOperation exception is thrown with AWS Redshift.

• asyncpg version: 0.23.0
• PostgreSQL version: PostgreSQL 8.0.2 on i686-pc-linux-gnu, compiled by GCC gcc (GCC) 3.4.2 20041017 (Red Hat 3.4.2-6.fc3), Redshift 1.0.27314
• Do you use a PostgreSQL SaaS? If so, which? Can you reproduce
  the issue with a local PostgreSQL install?: AWS Redshift.
• Python version: 3.6.13
• Platform: Linux 5.0.0-23-generic #24~18.04.1-Ubuntu SMP Mon Jul 29 16:12:28 UTC 2019 x86_64 x86_64 x86_64 GNU/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?: no
• Can the issue be reproduced under both asyncio and
  uvloop?: no

I am trying to use asyncpg with AWS Redshift. I got an decimal.InvalidOperation exception when I try to run a simple query as follows. Is there any way to make asyncpg work with AWS Redshift? psycopg2 is working with AWS Redshift without major issue so I expect asyncpg could work with AWS Redshift also. Thank you in advance.

import asyncio
import asyncpg

async def run():
    conn = await asyncpg.connect(
        user='user', password='password', database='database', host='host')
    values = await conn.fetch('SELECT 1.0 / 0.5')
    await conn.close()

loop = asyncio.get_event_loop()
loop.run_until_complete(run())

$ python asyncpg_redshift.py
Traceback (most recent call last):
  File "asyncpg_redshift.py", line 11, in <module>
    loop.run_until_complete(run())
  File "/home/taeho/.pyenv/versions/3.6.13/lib/python3.6/asyncio/base_events.py", line 488, in run_until_complete
    return future.result()
  File "asyncpg_redshift.py", line 7, in run
    values = await conn.fetch('SELECT 1.0 / 0.5')
  File "/home/taeho/.pyenv/versions/3.6.13/envs/asyncpg/lib/python3.6/site-packages/asyncpg/connection.py", line 588, in fetch
    record_class=record_class,
  File "/home/taeho/.pyenv/versions/3.6.13/envs/asyncpg/lib/python3.6/site-packages/asyncpg/connection.py", line 1632, in _execute
    ignore_custom_codec=ignore_custom_codec,
  File "/home/taeho/.pyenv/versions/3.6.13/envs/asyncpg/lib/python3.6/site-packages/asyncpg/connection.py", line 1655, in __execute
    ignore_custom_codec=ignore_custom_codec,
  File "/home/taeho/.pyenv/versions/3.6.13/envs/asyncpg/lib/python3.6/site-packages/asyncpg/connection.py", line 1697, in _do_execute
    result = await executor(stmt, None)
  File "asyncpg/protocol/protocol.pyx", line 201, in bind_execute
  File "asyncpg/protocol/coreproto.pyx", line 70, in asyncpg.protocol.protocol.CoreProtocol._read_server_messages
  File "asyncpg/protocol/coreproto.pyx", line 212, in asyncpg.protocol.protocol.CoreProtocol._process__bind_execute
  File "asyncpg/protocol/coreproto.pyx", line 497, in asyncpg.protocol.protocol.CoreProtocol._parse_data_msgs
  File "asyncpg/protocol/protocol.pyx", line 781, in asyncpg.protocol.protocol.BaseProtocol._decode_row
  File "asyncpg/protocol/prepared_stmt.pyx", line 295, in asyncpg.protocol.protocol.PreparedStatementState._decode_row
  File "asyncpg/protocol/codecs/base.pyx", line 289, in asyncpg.protocol.protocol.Codec.decode
  File "asyncpg/protocol/codecs/base.pyx", line 196, in asyncpg.protocol.protocol.Codec.decode_scalar
  File "asyncpg/pgproto/./codecs/numeric.pyx", line 287, in asyncpg.pgproto.pgproto.numeric_decode_binary
  File "asyncpg/pgproto/./codecs/numeric.pyx", line 279, in asyncpg.pgproto.pgproto.numeric_decode_binary_ex
decimal.InvalidOperation: [<class 'decimal.ConversionSyntax'>]
$

I think the strange result of the following query could be also related.

import asyncio
import asyncpg

async def run():
    conn = await asyncpg.connect(
        user='user', password='password', database='database', host='host')
    values = await conn.fetch('SELECT CAST(1.0 AS DECIMAL(10, 1))')
    print(values)
    await conn.close()

loop = asyncio.get_event_loop()
loop.run_until_complete(run())

$ python asyncpg_redshift2.py
[<Record numeric=Decimal('100000.00')>]
$ 

Commencez par exécuter les deux requêtes Python fournies sur AWS Redshift et comparez leurs résultats avec le traceback. Examinez asyncpg/pgproto/./codecs/numeric.pyx, où l’échec se produit lors du décodage numérique, et déterminez en quoi les données numériques renvoyées par Redshift diffèrent de la représentation attendue par PostgreSQL. La tâche est terminée lorsque l’incompatibilité est reproduite et qu’un comportement pris en charge ou un correctif limité est établi.