Re: encoding confusion

Sim Zacks wrote:
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> {BACKGROUND]
> I am testing dbmail for our corporate email solution.
>
> We originally tested it on mysql and now we are migrating it to postgresql.
>
> The messages are stored in a longblob field on mysql and a bytea field
> in postgresql.
>
> I set the database up as UTF-8

Not relevant if you're using bytea. Encoding is for character-based
types (varchar, text) not byte-based types.

[snip]
> When I used pygresql's escape_bytea function to copy the data, it went
> smoothly, but the data was corrupt.
> When I tried the escape_string function it died because the data it was
> moving was not UTF-8.

Your Python script seems to think it's dealing it's dealing with text
rather than a stream of bytes too. I'm not a Python programmer, but I'd
guess it's treating one of the database fields (either MySQL or
PostgreSQL) as text not bytes. You'll need to check the docs for
binary-data handling in your Python libraries.

I'm puzzled as to how the data was corrupted with escape_bytea() - I
can't imagine it would be that difficult for the library to get right.
I'd be suspicious that the source data wasn't what I thought it was.

> [CONFUSION]
> What I don't understand, is that if that database can't handle the non
> UTF characters, how does it allow them in when I receive an email
> (tested, it works) and when I restored the backup.
> I also don't understand why the data transfer didn't work to a UTF
> database, but it worked to an ASCII database, if the data can go into a
> UTF database from an ascii database.

Whatever is going on, it's nothing to do with the bytea type.

> Lastly, I wanted to know if anybody has experience moving data from
> mysql to postgresql and if what I did is considered normal, or if there
> is a better way of doing this.

I think that something in the process is trying to be clever and
treating the blobs as text.

--
Richard Huxton
Archonet Ltd