----- Original Message -----
From: "Alexey Pechnikov"
Newsgroups: gmane.comp.db.sqlite.general
Sent: Saturday, May 08, 2010 2:27 PM
Subject: Re: Returning column to default
Please send to me this patch. I think it may be added to unofficial
http://sqlite.mobigroup.ru repository.
No problems. It should be attached here. If not, send me your email and
I'll forward it direct to you. Its created against the latest released
version (3.6.23.1)
So that you know, this patch exploits a undocumented/unexpected state in the
update column expression. If this expression is set to NULL, then sqlite
will crash by default (this is not a problem generally since you can't/don't
ordinarily set the expression to NULL). I use this as the indicator to set
to default value. It then extracts the default expression from the table
column definition and applies it. Note that it must duplicate it since it
will later be cleaned up automatically.
If there is no column default then an error occurs ("no default for column:
x"). This could easily be changed, if desired, to setting the column as
NULL, for example, but to me it makes more sense to have the error.
The attached test file can be placed in the 'test' folder along with all the
others and will then run along with them when doing a "make test".
As stated before, I'd be very interested to have feedback on how well it
works for you. I can't claim to have tested it exhaustively (e.g. as the
test file shows!), but would be happy to augment it and fix any bugs that
come up, assuming they're not too complex!!!
Cheers
Andy
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