BC dates result in error running the query

• asyncpg version: asyncpg=0.18.3=py37h1de35cc_0
• PostgreSQL version: PostgreSQL 11.1 on x86_64-apple-darwin18.2.0, compiled by Apple LLVM version 10.0.0 (clang-1000.11.45.5), 64-bit
• **Do you use a PostgreSQL SaaS? No
• Python version: 3.7
• Platform: osx
• 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?: Tried only asyncio

When a date or datetime column includes dates in the form of 0001-01-01 BC which are valid postgres dates, the driver returns the following:

    result = await executor(stmt, None)
  File "asyncpg/protocol/protocol.pyx", line 196, in bind_execute
  File "asyncpg/protocol/coreproto.pyx", line 65, in asyncpg.protocol.protocol.CoreProtocol._read_server_messages
  File "asyncpg/protocol/coreproto.pyx", line 202, in asyncpg.protocol.protocol.CoreProtocol._process__bind_execute
  File "asyncpg/protocol/coreproto.pyx", line 498, in asyncpg.protocol.protocol.CoreProtocol._parse_data_msgs
  File "asyncpg/protocol/protocol.pyx", line 754, in asyncpg.protocol.protocol.BaseProtocol._decode_row
  File "asyncpg/protocol/prepared_stmt.pyx", line 282, in asyncpg.protocol.protocol.PreparedStatementState._decode_row
  File "asyncpg/protocol/codecs/base.pyx", line 288, in asyncpg.protocol.protocol.Codec.decode
  File "asyncpg/protocol/codecs/base.pyx", line 195, in asyncpg.protocol.protocol.Codec.decode_scalar
  File "asyncpg/pgproto/./codecs/datetime.pyx", line 133, in asyncpg.pgproto.pgproto.date_decode
ValueError: ordinal must be >= 1

ValueError: ordinal must be >= 1

I assume this is some kind of a problem mapping from the BC date to a python date, however this is annoying since valid postgres tables can't be queries. At least in the interim it should be possible to return None if for some reason the date couldn't be parsed but not give up entirely. Is there a quick and dirty way around that?

从 asyncpg/pgproto/./codecs/datetime.pyx 中 traceback 所示的 date_decode 路径开始，使用包含 0001-01-01 BC 的 PostgreSQL date 或 datetime 重现该故障。检查现有的 date codec 测试，并确定 BC 值所支持的结果；完成标准是，解码此类行不再中止查询，并且该行为由回归测试覆盖。