SQLite3 in Python 2.7 Rejecting Foreign Key Insert

Chris Angelico rosuav at gmail.com
Sun Nov 23 03:22:10 CET 2014

On Sun, Nov 23, 2014 at 1:11 PM, llanitedave
<llanitedave at birdandflower.com> wrote:
> logging.info("Related borehole_id is %s, of_borehole is %s", relatedbh, runfields[1])
> In this case, the displayed data from both is identical -- the logging line comes back as:
> INFO:Related borehole_id is testbh3, of_borehole is testbh3
> So the data type is the same, and the content appears to be the same.  So why would there be a foreign key mismatch?  Is it possible that there is some invisible code in the string which isn't being detected by the logging command?  Is this just a quirk of the Sqlite3 implementation in Python that demands foreign keys be integers?

First thing I'd do, if I'm suspicious of invisible stuff in a string,
is to change those %s markers to %r. You'll get a quoted string (so
you can see if there's leading/trailing whitespace), any non-ASCII
characters will be escaped (assuming this is a byte string in Python
2, which seems to be the case), and control characters like newlines
will become escapes too.

But I've seen a number of very strange and annoying behaviours out of
SQLite as regards foreign keys. It seems that sometimes integrity
checks just aren't being done, and I don't know why. Can you switch to
a PostgreSQL back-end to see if the problem (a) suddenly disappears,
(b) suddenly appears at a completely different point, or (c) now has a
more informative error message? Chances are all you need to do is
change your import and connection setup, and all the rest will work
just the same.

By the way, naming convention: I prefer to use "id" only when it's
actually a numeric ID. For something like this, I'd call it "name",
since that's what it is. But that won't be affecting your foreign key.


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