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From: Oleg B. <ph...@ph...> - 2013-06-05 07:16:00
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On Wed, Jun 05, 2013 at 08:54:20AM +0200, Thomas Siemion <de...@af...> wrote:
> Hey folks,
>
> I was wondering why the sqlrepr from converters.py is escaping
> linebreaks and other chars for postgres.
>
> I'm talking about this piece of code:
>
> sqlStringReplace = [
> ("'", "''"),
> ('\\', '\\\\'),
> ('\000', '\\0'),
> ('\b', '\\b'),
> ('\n', '\\n'),
> ('\r', '\\r'),
> ('\t', '\\t'),
> ]
>
> This causes for e.g. \ to multiply. when I comment out everything but
> the escaping of the single quote everything works as aspected. I don't
> see the reason why this is done in the first place.
>
> Could anyone please explain this to me and why this is done when saving
See
http://www.postgresql.org/docs/8.4/static/sql-syntax-lexical.html#SQL-SYNTAX-CONSTANTS
"PostgreSQL also accepts "escape" string constants, which are an
extension to the SQL standard. An escape string constant is specified by
writing the letter E (upper or lower case) just before the opening
single quote, e.g., E'foo'. (When continuing an escape string constant
across lines, write E only before the first opening quote.) Within an
escape string, a backslash character (\) begins a C-like backslash
escape sequence, in which the combination of backslash and following
character(s) represent a special byte value, as shown in Table 4-1."
Also see https://dev.mysql.com/doc/refman/5.0/en/string-literals.html
> but not undone when loaing?
Because there is no need to "undone" anything. The backend doesn't
store escaped values -- it stores normal values that it sends back on
SELECTing.
> Regards
> Thomas
Oleg.
--
Oleg Broytman http://phdru.name/ ph...@ph...
Programmers don't die, they just GOSUB without RETURN.
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