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bpo-44958: Only reset sqlite3 statements when needed (GH-27844)
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Erlend Egeberg Aasland authored Sep 21, 2021
1 parent debd804 commit 050d103
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Showing 4 changed files with 82 additions and 46 deletions.
49 changes: 42 additions & 7 deletions Lib/sqlite3/test/test_regression.py
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Original file line number Diff line number Diff line change
Expand Up @@ -124,13 +124,14 @@ def test_type_map_usage(self):
"""
SELECT = "select * from foo"
con = sqlite.connect(":memory:",detect_types=sqlite.PARSE_DECLTYPES)
con.execute("create table foo(bar timestamp)")
con.execute("insert into foo(bar) values (?)", (datetime.datetime.now(),))
con.execute(SELECT).close()
con.execute("drop table foo")
con.execute("create table foo(bar integer)")
con.execute("insert into foo(bar) values (5)")
con.execute(SELECT).close()
cur = con.cursor()
cur.execute("create table foo(bar timestamp)")
cur.execute("insert into foo(bar) values (?)", (datetime.datetime.now(),))
cur.execute(SELECT)
cur.execute("drop table foo")
cur.execute("create table foo(bar integer)")
cur.execute("insert into foo(bar) values (5)")
cur.execute(SELECT)

def test_bind_mutating_list(self):
# Issue41662: Crash when mutate a list of parameters during iteration.
Expand Down Expand Up @@ -435,6 +436,40 @@ def test_return_empty_bytestring(self):
val = cur.fetchone()[0]
self.assertEqual(val, b'')

def test_table_lock_cursor_replace_stmt(self):
con = sqlite.connect(":memory:")
cur = con.cursor()
cur.execute("create table t(t)")
cur.executemany("insert into t values(?)", ((v,) for v in range(5)))
con.commit()
cur.execute("select t from t")
cur.execute("drop table t")
con.commit()

def test_table_lock_cursor_dealloc(self):
con = sqlite.connect(":memory:")
con.execute("create table t(t)")
con.executemany("insert into t values(?)", ((v,) for v in range(5)))
con.commit()
cur = con.execute("select t from t")
del cur
con.execute("drop table t")
con.commit()

def test_table_lock_cursor_non_readonly_select(self):
con = sqlite.connect(":memory:")
con.execute("create table t(t)")
con.executemany("insert into t values(?)", ((v,) for v in range(5)))
con.commit()
def dup(v):
con.execute("insert into t values(?)", (v,))
return
con.create_function("dup", 1, dup)
cur = con.execute("select dup(t) from t")
del cur
con.execute("drop table t")
con.commit()


if __name__ == "__main__":
unittest.main()
45 changes: 19 additions & 26 deletions Modules/_sqlite/cursor.c
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Original file line number Diff line number Diff line change
Expand Up @@ -104,12 +104,7 @@ cursor_clear(pysqlite_Cursor *self)
Py_CLEAR(self->row_cast_map);
Py_CLEAR(self->lastrowid);
Py_CLEAR(self->row_factory);
if (self->statement) {
/* Reset the statement if the user has not closed the cursor */
pysqlite_statement_reset(self->statement);
Py_CLEAR(self->statement);
}

Py_CLEAR(self->statement);
return 0;
}

Expand All @@ -121,6 +116,14 @@ cursor_dealloc(pysqlite_Cursor *self)
if (self->in_weakreflist != NULL) {
PyObject_ClearWeakRefs((PyObject*)self);
}
if (self->statement) {
/* A SELECT query will lock the affected database table(s), so we need
* to reset the statement to unlock the database before disappearing */
sqlite3_stmt *stmt = self->statement->st;
if (sqlite3_stmt_readonly(stmt)) {
pysqlite_statement_reset(self->statement);
}
}
tp->tp_clear((PyObject *)self);
tp->tp_free(self);
Py_DECREF(tp);
Expand Down Expand Up @@ -515,18 +518,19 @@ _pysqlite_query_execute(pysqlite_Cursor* self, int multiple, PyObject* operation
}
}

if (self->statement != NULL) {
/* There is an active statement */
pysqlite_statement_reset(self->statement);
}

/* reset description and rowcount */
Py_INCREF(Py_None);
Py_SETREF(self->description, Py_None);
self->rowcount = 0L;

if (self->statement) {
(void)pysqlite_statement_reset(self->statement);
/* A SELECT query will lock the affected database table(s), so we need
* to reset the statement to unlock the database before switching
* statements */
sqlite3_stmt *stmt = self->statement->st;
if (sqlite3_stmt_readonly(stmt)) {
pysqlite_statement_reset(self->statement);
}
}

PyObject *stmt = get_statement_from_cache(self, operation);
Expand All @@ -549,8 +553,6 @@ _pysqlite_query_execute(pysqlite_Cursor* self, int multiple, PyObject* operation
goto error;
}
}

pysqlite_statement_reset(self->statement);
pysqlite_statement_mark_dirty(self->statement);

/* We start a transaction implicitly before a DML statement.
Expand All @@ -570,6 +572,7 @@ _pysqlite_query_execute(pysqlite_Cursor* self, int multiple, PyObject* operation
break;
}

pysqlite_statement_reset(self->statement);
pysqlite_statement_mark_dirty(self->statement);

pysqlite_statement_bind_parameters(state, self->statement, parameters);
Expand All @@ -587,7 +590,6 @@ _pysqlite_query_execute(pysqlite_Cursor* self, int multiple, PyObject* operation
PyErr_Clear();
}
}
(void)pysqlite_statement_reset(self->statement);
_pysqlite_seterror(state, self->connection->db);
goto error;
}
Expand Down Expand Up @@ -646,13 +648,9 @@ _pysqlite_query_execute(pysqlite_Cursor* self, int multiple, PyObject* operation
}

if (rc == SQLITE_DONE && !multiple) {
pysqlite_statement_reset(self->statement);
Py_CLEAR(self->statement);
}

if (multiple) {
pysqlite_statement_reset(self->statement);
}
Py_XDECREF(parameters);
}

Expand Down Expand Up @@ -804,7 +802,6 @@ pysqlite_cursor_iternext(pysqlite_Cursor *self)
sqlite3_stmt *stmt = self->statement->st;
assert(stmt != NULL);
if (sqlite3_data_count(stmt) == 0) {
(void)pysqlite_statement_reset(self->statement);
Py_CLEAR(self->statement);
return NULL;
}
Expand All @@ -815,7 +812,7 @@ pysqlite_cursor_iternext(pysqlite_Cursor *self)
}
int rc = pysqlite_step(stmt);
if (rc == SQLITE_DONE) {
(void)pysqlite_statement_reset(self->statement);
Py_CLEAR(self->statement);
}
else if (rc != SQLITE_ROW) {
(void)_pysqlite_seterror(self->connection->state,
Expand Down Expand Up @@ -985,11 +982,7 @@ pysqlite_cursor_close_impl(pysqlite_Cursor *self, PyTypeObject *cls)
return NULL;
}

if (self->statement) {
(void)pysqlite_statement_reset(self->statement);
Py_CLEAR(self->statement);
}

Py_CLEAR(self->statement);
self->closed = 1;

Py_RETURN_NONE;
Expand Down
32 changes: 20 additions & 12 deletions Modules/_sqlite/statement.c
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Original file line number Diff line number Diff line change
Expand Up @@ -360,23 +360,31 @@ pysqlite_statement_bind_parameters(pysqlite_state *state,
}
}

int pysqlite_statement_reset(pysqlite_Statement* self)
void
pysqlite_statement_reset(pysqlite_Statement *self)
{
int rc;
sqlite3_stmt *stmt = self->st;
if (stmt == NULL || self->in_use == 0) {
return;
}

rc = SQLITE_OK;
#if SQLITE_VERSION_NUMBER >= 3020000
/* Check if the statement has been run (that is, sqlite3_step() has been
* called at least once). Third parameter is non-zero in order to reset the
* run count. */
if (sqlite3_stmt_status(stmt, SQLITE_STMTSTATUS_RUN, 1) == 0) {
return;
}
#endif

if (self->in_use && self->st) {
Py_BEGIN_ALLOW_THREADS
rc = sqlite3_reset(self->st);
Py_END_ALLOW_THREADS
int rc;
Py_BEGIN_ALLOW_THREADS
rc = sqlite3_reset(stmt);
Py_END_ALLOW_THREADS

if (rc == SQLITE_OK) {
self->in_use = 0;
}
if (rc == SQLITE_OK) {
self->in_use = 0;
}

return rc;
}

void pysqlite_statement_mark_dirty(pysqlite_Statement* self)
Expand Down
2 changes: 1 addition & 1 deletion Modules/_sqlite/statement.h
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Original file line number Diff line number Diff line change
Expand Up @@ -44,7 +44,7 @@ void pysqlite_statement_bind_parameters(pysqlite_state *state,
pysqlite_Statement *self,
PyObject *parameters);

int pysqlite_statement_reset(pysqlite_Statement* self);
void pysqlite_statement_reset(pysqlite_Statement *self);
void pysqlite_statement_mark_dirty(pysqlite_Statement* self);

int pysqlite_statement_setup_types(PyObject *module);
Expand Down

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