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bpo-33376: clear cursor->statement when setting cursor->reset #10250

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bpo-33376: clear cursor->statement when setting cursor->reset #10250

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Fix issue33376: clear cursor->statement when setting cursor->reset
cyang1 Oct 30, 2018
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cyang1 Oct 30, 2018
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42 changes: 42 additions & 0 deletions Lib/sqlite3/test/regression.py
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Original file line number Diff line number Diff line change
Expand Up @@ -381,6 +381,48 @@ def CheckCommitCursorReset(self):
counter += 1
self.assertEqual(counter, 3, "should have returned exactly three rows")

def CheckActionAfterRollbackCursorReset(self):
"""
Similar to `CheckCommitCursorReset`, `Connection::rollback()` resets
statements and cursors, which could cause statements to be reset again
when they shouldn't be.

See issue33376 for more details.
"""
con = sqlite.connect(":memory:")
con.executescript("""
create table t(c);
insert into t values(0);
insert into t values(1);
insert into t values(2);
""")

self.assertEqual(con.isolation_level, "")

curs = con.cursor()
curs.execute("BEGIN TRANSACTION")
curs.execute("select c from t")
con.rollback()

# Reusing the same statement from the statement cache, which has been
# reset by the rollback above.
gen = con.execute("select c from t")

# Would previously cause a spurious reset of the statement.
del curs

counter = 0
for i, row in enumerate(gen):
with self.subTest(i=i, row=row):
if counter == 0:
self.assertEqual(row[0], 0)
elif counter == 1:
self.assertEqual(row[0], 1)
elif counter == 2:
self.assertEqual(row[0], 2)

@mgedmin mgedmin Feb 8, 2019

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Why not self.assertEqual(row[0], counter)?

@cyang1 cyang1 Jul 10, 2020

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For consistency with the previous, very similar unit test. I don't have particularly strong opinions either way, but I generally value correctness > consistency > style.

I can change it if others feel strongly about this.

counter += 1
self.assertEqual(counter, 3, "should have returned exactly three rows")

def CheckBpo31770(self):
"""
The interpreter shouldn't crash in case Cursor.__init__() is called
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2018-10-30-14-34-26.bpo-33376.D4Xydk.rst
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@@ -0,0 +1,2 @@
Fixes spurious statement resets after a connection rollback in some
situations.
1 change: 1 addition & 0 deletions Modules/_sqlite/connection.c
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Expand Up @@ -238,6 +238,7 @@ void pysqlite_do_all_statements(pysqlite_Connection* self, int action, int reset
cursor = (pysqlite_Cursor*)PyWeakref_GetObject(weakref);
if ((PyObject*)cursor != Py_None) {
cursor->reset = 1;
Py_CLEAR(cursor->statement);
}
}
}
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