Chason Hayes wrote:
> On Tue, 07 Feb 2006 01:58:00 +0000, Steve Holden wrote:
>
>
>>Chason Hayes wrote:
>>
>>>On Mon, 06 Feb 2006 13:39:17 +0000, Steve Holden wrote:
>>
>>[...]
>>
>>>>The URL you reference is discussing how you represent arbitrary values
>>>>in string literals. If you already have the data in a Python string the
>>>>best advise is to use a parameterized query - that way your Python DB
>>>>API module will do the escaping for you!
>>>>
>>>>regards
>>>> Steve
>>>
>>>
>>>Thanks for the input. I tried that with a format string and a
>>>dictionary, but I still received a database error indicating illegal
>>>string values. This error went away completely when I used a test file
>>>consisting only of text, but reproduced everytime with a true binary file.
>>>If you can let me know where I am wrong or show me a code snippet with a
>>>sql insert that contains a variable with raw binary data that works,
>>>I would greatly appreciate it.
>>>
>>
>>I tried and my experience was exactly the same, which made me think less
>>of PostgreSQL.
>>
>>They don't seem to implement the SQL BLOB type properly, so it looks as
>>though that rebarbative syntax with all the backslashes is necessary. Sorry.
>>
>>regards
>> Steve
>
>
> with regards to escaping data parameters I have found that I have to
> specifically add quotes to my strings for them to be understood by
> pstgresql. For example
>
> ifs=open("binarydatafile","r")
> binarydata=ifs.read()
> stringdata=base64.encodestring(binarydata)
>
> #does not work
> cursor.execute("insert into binarytable values(%s)" % stringdata)
>
> #need to do this first
> newstringdata = "'" + stringdata + "'"
>
> then the select statment works.
> Is this expected behavior? Is there a better way of doing this?
>
> thanks for any insight
Yes, parameterize your queries. I assume you are using psycopg or
something similar to create the database connection (i.e. I something
that expects the "%s" parameter style - there are other options, but we
needn't discuss them here).
The magic incantation you seek is:
cursor.execute("insert into binarytable values(%s)", (stringdata, ))
Note that here there are TWO arguments to the .execute() method. The
first is a parameterized SQL statement, and the second is a tuple of
data items, one for each parameter mark in the SQL.
Using this technique all necessary quoting (and even data conversion
with a good database module) is performed inside the database driver,
meaning (among other things) that your program is no longer vulnerable
to the dreaded SQL injection errors.
This is the technique I was hoping would work with the bytea datatype,
but alas it doesn't. ISTM that PostgreSQL needs a bit of work there,
even though it is otherwise a very polished product.
regards
Steve
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