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POsqlite3 foreign keys "remembered"?
 

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  1. POsqlite3 foreign keys "remembered"?
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    <p>I really, really hope I'm simply doing something wrong.</p> <p>I have two tables and a mapping table; the latter's two columns reference the respective primary keys of the others. Deleting one of the data rows does not work if a mapping exists; this is expected. However, deleting the mapping should allow me to delete the data row, but I get an IntegrityError when I try to do so.</p> <p>Example code:</p> <pre><code>import sqlite3 conn = sqlite3.connect(':memory:') conn.execute('PRAGMA foreign_keys = ON') fk = (conn.execute("PRAGMA foreign_keys").fetchone()[0]) print 'version = %s, foreign keys = %r' % (sqlite3.sqlite_version, bool(fk)) if not fk: raise Exception('No foreign keys!?') c = conn.cursor() c.executescript(''' create table if not exists main.one (resource_id TEXT PRIMARY KEY, data TEXT); create table if not exists main.two (node_id INTEGER PRIMARY KEY, data TEXT); create table if not exists main.mapping (node_id INTEGER REFERENCES two, resource_id TEXT REFERENCES one); insert into main.one(resource_id, data) values('A', 'A one thing'); insert into main.two(node_id, data) values(1, 'A two thing'); insert into main.mapping(resource_id, node_id) values('A', 1); insert into main.one(resource_id, data) values('B', 'Another one thing'); insert into main.two(node_id, data) values(2, 'Another two thing'); insert into main.mapping(resource_id, node_id) values('B', 2); insert into main.one(resource_id, data) values('C', 'Yet another one thing'); ''') for tbl in 'one', 'two', 'mapping': print 'TABLE main.%s:\n%s\n' % (tbl, '\n'.join(repr(r) for r in c.execute('select * from main.%s' % tbl).fetchall())) del_cmd = """delete from main.one where resource_id='B'""" print 'Attempting: %s' % (del_cmd,) try: c.execute(del_cmd) except Exception, e: print 'Failed to delete: %s' % e cmd = """delete from main.one where resource_id='C'""" print 'Attempting: %s' % (cmd,) c.execute(cmd) cmd = """delete from main.mapping where resource_id='B' AND node_id=2""" print '\nAttempting: %s' % (cmd,) c.execute(cmd) for tbl in 'one', 'two', 'mapping': print 'TABLE main.%s:\n%s\n' % (tbl, '\n'.join(repr(r) for r in c.execute('select * from main.%s' % tbl).fetchall())) print 'Attempting: %s' % (del_cmd,) c.execute(del_cmd) </code></pre> <p>I'd expect all of that to print the various table contents and progress. However, the very last DELETE violates a foreign key constraint that I cannot find:</p> <pre><code>$ python test.py version = 3.6.22, foreign keys = True TABLE main.one: (u'A', u'A one thing') (u'B', u'Another one thing') (u'C', u'Yet another one thing') TABLE main.two: (1, u'A two thing') (2, u'Another two thing') TABLE main.mapping: (1, u'A') (2, u'B') Attempting: delete from main.one where resource_id='B' Failed to delete: foreign key constraint failed Attempting: delete from main.one where resource_id='C' Attempting: delete from main.mapping where resource_id='B' AND node_id=2 TABLE main.one: (u'A', u'A one thing') (u'B', u'Another one thing') TABLE main.two: (1, u'A two thing') (2, u'Another two thing') TABLE main.mapping: (1, u'A') Attempting: delete from main.one where resource_id='B' Traceback (most recent call last): File "/tmp/test.py", line 49, in &lt;module&gt; c.execute(del_cmd) sqlite3.IntegrityError: foreign key constraint failed </code></pre> <p>WTF?</p>
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    1. PTQuestion
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    1. USGabe
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      1. VTUpMod
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      1. VTUpMod
    1. COCan you simplify the code presentation of the problem? I'd like to take a look but I'm not wading through all that, and many others won't either. Make a minimal demo and who knows, maybe the answer will pop out at you...
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      1. USalexis
    2. COI cut and pasted your code exactly as posted, and it ran fine, the delete didn't fail, and printing the tables afterward shows the row was deleted.
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      1. USsnapshoe
    3. COmita, which sqlite and python version?
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      1. USGabe
 

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