Re: [COMMITTERS] pgsql: Fix mapping of PostgreSQL encodings to Python encodings.

On 05/07/12 22:37, Heikki Linnakangas wrote:
> On 05.07.2012 23:31, Tom Lane wrote:
>> Heikki Linnakangas<heikki.linnakangas@iki.fi> writes:
>>> Fix mapping of PostgreSQL encodings to Python encodings.
>>
>> The buildfarm doesn't like this --- did you check for side effects on
>> regression test results?
>
> Hmm, I ran the regressions tests, but not with C encoding. With the
> patch, you no longer get the errdetail you used to, when an encoding
> conversion fails:
>
>> ***************
>> *** 41,47 ****
>>
>> SELECT unicode_plan1();
>> ERROR: spiexceptions.InternalError: could not convert Python Unicode
>> object to PostgreSQL server encoding
>> - DETAIL: UnicodeEncodeError: 'ascii' codec can't encode character
>> u'\x80' in position 0: ordinal not in range(128)
>> CONTEXT: Traceback (most recent call last):
>> PL/Python function "unicode_plan1", line 3, in <module>
>> rv = plpy.execute(plan, [u"\x80"], 1)
>> --- 39,44 ----
>
> We could just update the expected output, there's two expected outputs
> for this test case and one of them is now wrong. But it'd actually be
> quite a shame to lose that extra information, that's quite valuable.
> Perhaps we should go back to using PLu_elog() here, and find some other
> way to avoid the recursion.

Seems that the problem is that the LC_ALL=C makes Postgres use SQL_ASCII 
as the database encoding and as the comment states, translating PG's 
SQL_ASCII to Python's "ascii" is not ideal.

The problem is that PLyUnicode_Bytes is (via an ifdef) used as 
PyString_ToString on Python3, which means that there are numerous call 
sites and new ones might appear in any moment. I'm not that keen on 
invoking the traceback machinery on low-level encoding errors.

Hm, since PyUnicode_Bytes should get a unicode object and return bytes 
in the server encoding, we might just say that for SQL_ASCII we 
arbitrarily choose UTF-8 to encode the unicode codepoints, so we'd just 
set serverenc = "utf-8" in the first switch case.

That doesn't solve the problem of the missing error detail, though.

Jan